WO2000029365A2 - Preparation of polyoxymethylene dimethyl ethers by acid-activated catalytic conversion of methanol with formaldehyde - Google Patents
Preparation of polyoxymethylene dimethyl ethers by acid-activated catalytic conversion of methanol with formaldehyde Download PDFInfo
- Publication number
- WO2000029365A2 WO2000029365A2 PCT/US1999/020751 US9920751W WO0029365A2 WO 2000029365 A2 WO2000029365 A2 WO 2000029365A2 US 9920751 W US9920751 W US 9920751W WO 0029365 A2 WO0029365 A2 WO 0029365A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- formaldehyde
- methanol
- mixture
- catalyst
- dimethyl ether
- Prior art date
Links
- -1 polyoxymethylene dimethyl ethers Polymers 0.000 title claims abstract description 61
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 title claims description 44
- 238000002360 preparation method Methods 0.000 title description 8
- 239000002253 acid Substances 0.000 title description 5
- REHUGJYJIZPQAV-UHFFFAOYSA-N formaldehyde;methanol Chemical compound OC.O=C REHUGJYJIZPQAV-UHFFFAOYSA-N 0.000 title description 3
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims abstract description 446
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 425
- 239000003054 catalyst Substances 0.000 claims abstract description 142
- 238000000034 method Methods 0.000 claims abstract description 70
- 230000002378 acidificating effect Effects 0.000 claims abstract description 55
- 230000008569 process Effects 0.000 claims abstract description 50
- NKDDWNXOKDWJAK-UHFFFAOYSA-N dimethoxymethane Chemical compound COCOC NKDDWNXOKDWJAK-UHFFFAOYSA-N 0.000 claims abstract description 41
- 238000004821 distillation Methods 0.000 claims abstract description 37
- 238000009833 condensation Methods 0.000 claims abstract description 23
- 230000005494 condensation Effects 0.000 claims abstract description 23
- 230000001737 promoting effect Effects 0.000 claims abstract description 22
- 230000003213 activating effect Effects 0.000 claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 14
- 239000003957 anion exchange resin Substances 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 9
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims description 230
- 239000000203 mixture Substances 0.000 claims description 86
- 239000007788 liquid Substances 0.000 claims description 82
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 60
- 229910001868 water Inorganic materials 0.000 claims description 49
- 238000001179 sorption measurement Methods 0.000 claims description 48
- 239000007789 gas Substances 0.000 claims description 45
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 37
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 36
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 34
- 229910001882 dioxygen Inorganic materials 0.000 claims description 33
- 239000000446 fuel Substances 0.000 claims description 32
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 26
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 24
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 claims description 24
- 238000007254 oxidation reaction Methods 0.000 claims description 24
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 23
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 20
- 230000003647 oxidation Effects 0.000 claims description 20
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 19
- 230000015572 biosynthetic process Effects 0.000 claims description 19
- 239000011701 zinc Substances 0.000 claims description 19
- 229910052725 zinc Inorganic materials 0.000 claims description 19
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 18
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 18
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims description 18
- 229910052802 copper Inorganic materials 0.000 claims description 18
- 239000010949 copper Substances 0.000 claims description 18
- 235000019253 formic acid Nutrition 0.000 claims description 18
- 229910052711 selenium Inorganic materials 0.000 claims description 18
- 239000011669 selenium Substances 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 15
- 239000003085 diluting agent Substances 0.000 claims description 15
- 238000004519 manufacturing process Methods 0.000 claims description 15
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 14
- 239000001569 carbon dioxide Substances 0.000 claims description 13
- 229910052709 silver Inorganic materials 0.000 claims description 13
- 239000004332 silver Substances 0.000 claims description 13
- 239000003729 cation exchange resin Substances 0.000 claims description 12
- 229910052714 tellurium Inorganic materials 0.000 claims description 12
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims description 12
- 239000008246 gaseous mixture Substances 0.000 claims description 11
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 claims description 11
- 238000005839 oxidative dehydrogenation reaction Methods 0.000 claims description 11
- 229910001930 tungsten oxide Inorganic materials 0.000 claims description 11
- 229920001577 copolymer Polymers 0.000 claims description 9
- 239000012808 vapor phase Substances 0.000 claims description 9
- 150000002894 organic compounds Chemical class 0.000 claims description 8
- 229910052717 sulfur Inorganic materials 0.000 claims description 8
- 239000011593 sulfur Substances 0.000 claims description 8
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 7
- 229940023913 cation exchange resins Drugs 0.000 claims description 7
- 239000011347 resin Substances 0.000 claims description 7
- 229920005989 resin Polymers 0.000 claims description 7
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims description 6
- 238000009835 boiling Methods 0.000 claims description 6
- 238000002485 combustion reaction Methods 0.000 claims description 6
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 150000007524 organic acids Chemical class 0.000 claims description 3
- 235000005985 organic acids Nutrition 0.000 claims description 3
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 claims description 3
- 229910052901 montmorillonite Inorganic materials 0.000 claims description 2
- 229910000278 bentonite Inorganic materials 0.000 claims 1
- 239000000440 bentonite Substances 0.000 claims 1
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 claims 1
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 claims 1
- MYRTYDVEIRVNKP-UHFFFAOYSA-N divinylbenzene Substances C=CC1=CC=CC=C1C=C MYRTYDVEIRVNKP-UHFFFAOYSA-N 0.000 claims 1
- 239000002283 diesel fuel Substances 0.000 abstract description 15
- 235000019256 formaldehyde Nutrition 0.000 description 132
- 239000000047 product Substances 0.000 description 46
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 33
- 238000000066 reactive distillation Methods 0.000 description 26
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 24
- 239000000243 solution Substances 0.000 description 23
- 238000000926 separation method Methods 0.000 description 18
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 16
- 229930040373 Paraformaldehyde Natural products 0.000 description 15
- 238000003860 storage Methods 0.000 description 15
- 239000007921 spray Substances 0.000 description 14
- 229920002866 paraformaldehyde Polymers 0.000 description 13
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 12
- 239000000126 substance Substances 0.000 description 12
- 229910052757 nitrogen Inorganic materials 0.000 description 11
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 10
- 229910021536 Zeolite Inorganic materials 0.000 description 9
- 150000001335 aliphatic alkanes Chemical class 0.000 description 9
- 150000001875 compounds Chemical class 0.000 description 9
- 239000001257 hydrogen Substances 0.000 description 9
- 229910052739 hydrogen Inorganic materials 0.000 description 9
- 239000010457 zeolite Substances 0.000 description 9
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 8
- 239000007795 chemical reaction product Substances 0.000 description 8
- 239000008098 formaldehyde solution Substances 0.000 description 8
- 229920006324 polyoxymethylene Polymers 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 238000004891 communication Methods 0.000 description 7
- 229910044991 metal oxide Inorganic materials 0.000 description 7
- 235000012239 silicon dioxide Nutrition 0.000 description 7
- 239000006096 absorbing agent Substances 0.000 description 6
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 229920000642 polymer Polymers 0.000 description 6
- 239000010453 quartz Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000002360 explosive Substances 0.000 description 5
- 239000012530 fluid Substances 0.000 description 5
- 150000002484 inorganic compounds Chemical class 0.000 description 5
- 229910010272 inorganic material Inorganic materials 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 150000004706 metal oxides Chemical class 0.000 description 5
- 230000002829 reductive effect Effects 0.000 description 5
- 239000000779 smoke Substances 0.000 description 5
- 230000000153 supplemental effect Effects 0.000 description 5
- 238000003786 synthesis reaction Methods 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 239000002808 molecular sieve Substances 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 230000002441 reversible effect Effects 0.000 description 4
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 4
- BGJSXRVXTHVRSN-UHFFFAOYSA-N 1,3,5-trioxane Chemical compound C1OCOCO1 BGJSXRVXTHVRSN-UHFFFAOYSA-N 0.000 description 3
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 3
- 239000005751 Copper oxide Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 3
- 150000007513 acids Chemical class 0.000 description 3
- 229910000431 copper oxide Inorganic materials 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 239000011261 inert gas Substances 0.000 description 3
- 239000003456 ion exchange resin Substances 0.000 description 3
- 229920003303 ion-exchange polymer Polymers 0.000 description 3
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- JPJALAQPGMAKDF-UHFFFAOYSA-N selenium dioxide Chemical compound O=[Se]=O JPJALAQPGMAKDF-UHFFFAOYSA-N 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 2
- 150000001241 acetals Chemical class 0.000 description 2
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 2
- 229910000323 aluminium silicate Inorganic materials 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 238000010924 continuous production Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 239000000539 dimer Substances 0.000 description 2
- 150000005218 dimethyl ethers Chemical class 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012527 feed solution Substances 0.000 description 2
- 239000003502 gasoline Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000005984 hydrogenation reaction Methods 0.000 description 2
- OXVFDZYQLGRLCD-UHFFFAOYSA-N hydroxypioglitazone Chemical compound N1=CC(C(O)C)=CC=C1CCOC(C=C1)=CC=C1CC1C(=O)NC(=O)S1 OXVFDZYQLGRLCD-UHFFFAOYSA-N 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000012263 liquid product Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 235000010755 mineral Nutrition 0.000 description 2
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 2
- 239000011973 solid acid Substances 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 2
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- PFNQVRZLDWYSCW-UHFFFAOYSA-N (fluoren-9-ylideneamino) n-naphthalen-1-ylcarbamate Chemical compound C12=CC=CC=C2C2=CC=CC=C2C1=NOC(=O)NC1=CC=CC2=CC=CC=C12 PFNQVRZLDWYSCW-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical compound [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 1
- 239000005750 Copper hydroxide Substances 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 239000012494 Quartz wool Substances 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 230000029936 alkylation Effects 0.000 description 1
- 238000005804 alkylation reaction Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005899 aromatization reaction Methods 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 235000012216 bentonite Nutrition 0.000 description 1
- 229910052810 boron oxide Inorganic materials 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 229920001429 chelating resin Polymers 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 150000001879 copper Chemical class 0.000 description 1
- 229940116318 copper carbonate Drugs 0.000 description 1
- 229910001956 copper hydroxide Inorganic materials 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 1
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- GEZOTWYUIKXWOA-UHFFFAOYSA-L copper;carbonate Chemical compound [Cu+2].[O-]C([O-])=O GEZOTWYUIKXWOA-UHFFFAOYSA-L 0.000 description 1
- FMWMEQINULDRBI-UHFFFAOYSA-L copper;sulfite Chemical compound [Cu+2].[O-]S([O-])=O FMWMEQINULDRBI-UHFFFAOYSA-L 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 150000001983 dialkylethers Chemical class 0.000 description 1
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 1
- 125000004177 diethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- GZVBAOSNKYQKIT-UHFFFAOYSA-N dimethoxymethane Chemical compound COCOC.COCOC GZVBAOSNKYQKIT-UHFFFAOYSA-N 0.000 description 1
- KTFJRKWUACQCHF-UHFFFAOYSA-N dimethoxymethane;methanol Chemical compound OC.COCOC KTFJRKWUACQCHF-UHFFFAOYSA-N 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000001640 fractional crystallisation Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 150000002373 hemiacetals Chemical class 0.000 description 1
- 239000002638 heterogeneous catalyst Substances 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
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- 239000012535 impurity Substances 0.000 description 1
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- 238000006317 isomerization reaction Methods 0.000 description 1
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- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical group CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 1
- 239000002343 natural gas well Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000006187 pill Substances 0.000 description 1
- 229920001467 poly(styrenesulfonates) Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000008262 pumice Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- IRPLSAGFWHCJIQ-UHFFFAOYSA-N selanylidenecopper Chemical compound [Se]=[Cu] IRPLSAGFWHCJIQ-UHFFFAOYSA-N 0.000 description 1
- QYHFIVBSNOWOCQ-UHFFFAOYSA-N selenic acid Chemical compound O[Se](O)(=O)=O QYHFIVBSNOWOCQ-UHFFFAOYSA-N 0.000 description 1
- 229940000207 selenious acid Drugs 0.000 description 1
- MCAHWIHFGHIESP-UHFFFAOYSA-N selenous acid Chemical compound O[Se](O)=O MCAHWIHFGHIESP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 235000010265 sodium sulphite Nutrition 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
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- 239000007858 starting material Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 125000001273 sulfonato group Chemical group [O-]S(*)(=O)=O 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- LAJZODKXOMJMPK-UHFFFAOYSA-N tellurium dioxide Chemical compound O=[Te]=O LAJZODKXOMJMPK-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000003828 vacuum filtration Methods 0.000 description 1
- 229910001935 vanadium oxide Inorganic materials 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 150000003751 zinc Chemical class 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
- UGZADUVQMDAIAO-UHFFFAOYSA-L zinc hydroxide Chemical compound [OH-].[OH-].[Zn+2] UGZADUVQMDAIAO-UHFFFAOYSA-L 0.000 description 1
- 229910021511 zinc hydroxide Inorganic materials 0.000 description 1
- 229940007718 zinc hydroxide Drugs 0.000 description 1
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 1
- 229910000368 zinc sulfate Inorganic materials 0.000 description 1
- 229960001763 zinc sulfate Drugs 0.000 description 1
- GQLBMRKEAODAKR-UHFFFAOYSA-L zinc;selenate Chemical compound [Zn+2].[O-][Se]([O-])(=O)=O GQLBMRKEAODAKR-UHFFFAOYSA-L 0.000 description 1
- PEUPCBAALXHYHP-UHFFFAOYSA-L zinc;selenite Chemical compound [Zn+2].[O-][Se]([O-])=O PEUPCBAALXHYHP-UHFFFAOYSA-L 0.000 description 1
- HSYFJDYGOJKZCL-UHFFFAOYSA-L zinc;sulfite Chemical compound [Zn+2].[O-]S([O-])=O HSYFJDYGOJKZCL-UHFFFAOYSA-L 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L10/00—Use of additives to fuels or fires for particular purposes
- C10L10/08—Use of additives to fuels or fires for particular purposes for improving lubricity; for reducing wear
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/48—Preparation of compounds having groups
- C07C41/50—Preparation of compounds having groups by reactions producing groups
- C07C41/56—Preparation of compounds having groups by reactions producing groups by condensation of aldehydes, paraformaldehyde, or ketones
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L10/00—Use of additives to fuels or fires for particular purposes
- C10L10/02—Use of additives to fuels or fires for particular purposes for reducing smoke development
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Definitions
- the present invention relates to production of organic compounds, particularly polyoxymethylene dimethyl ethers, which are suitable components for blending into fuel having improved qualities for use in diesel engines. More specifically, it relates to providing a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst, and heating this feedstream with the heterogeneous acidic catalyst in a catalytic distillation column to convert methanol and formaldehyde present to methylal and higher polyoxymethylene dimethyl ethers and separate the methylal from the higher polyoxymethylene dimethyl ethers.
- the catalytic distillation column has a section containing an anion exchange resin whereby an essentially acid-free product is obtained which can be used directly as a blending component, or fractionated, as by further distillation, to provide more suitable components for blending into diesel fuel.
- Integrated processes of the invention also provide their own source of formaldehyde.
- the source of formaldehyde is an un-purified liquid stream derived from a mixture formed by oxidative dehydrogenation (oxy- dehydrogenation) of methanol, dimethyl ether and mixtures thereof using, for example, a catalyst based silver.
- methane is converted to methanol, and dimethyl ether is subsequently manufactured from methanol by passing a mixed vapor containing methanol and water over an alumina catalyst, as described in an article by Hutchings in New Scientist (3 July 1986) 35.
- Formaldehyde is a very important intermediate compound in the chemical industry.
- the extreme reactivity of the formaldehyde carbonyl group and the nature of the molecule as a basic building block has made formaldehyde an important feedstock for a wide variety of industrially important chemical compounds.
- formaldehyde has found its largest volume of application in the manufacture of phenol - formaldehyde resins, urea-formaldehyde resins and other polymers. Pure formaldehyde is quite uncommon since it polymerizes readily. It was usually obtained as an aqueous solution such as formalin, which contains only about 40 percent formaldehyde. However, more recently, formaldehyde is usually transported as an item of commerce in concentrations of 37 to 50 percent by weight.
- paraformaldehyde A solid source of formaldehyde called paraformaldehyde is also commercially available. Because of the reactivity of formaldehyde, its handling and separation require special attention. It is a gas above -19°C and is flammable or explosive in air at concentrations of about 7 to about 12 mol percent. Formaldehyde polymerizes with itself at temperatures below 100°C and more rapidly when water vapor or impurities are present. Since formaldehyde is usually transported in aqueous solutions of 50 percent by weight or lower concentration, producers have tended to locate close to markets and to ship the methanol raw material, which has a smaller volume.
- a catalytic distillation structure which comprises a catalyst component associated intimately with or surrounded by a resilient component, which component is comprised of at least 70 vol. percent open space for providing a matrix of substantially open space.
- resilient component are open-mesh, knitted, stainless wire (demister wire or an expanded aluminum); open-mesh, knitted, polymeric filaments of nylon, Teflon, etc.; and highly-open structure foamed material (reticulated polyurethane).
- the middle portion of the distillation column was furnished with stages from which the liquid components were withdrawn and pumped to the reactor units, which contained solid acid catalyst.
- the reactive solutions containing the resulting methylal were fed to the distillation column, where methylal was distilled as the overhead product.
- Polyoxymethylene dimethyl ethers are the best known members of the dialkyl ether polymers of formaldehyde. While diethyl and dipropyl polyoxymethylene ethers have been prepared, major attention has been given to the dimethyl ether polymers. Polyoxymethylene dimethyl ethers make up a homologous series of polyoxymethylene glycol derivatives having the structure represented by use of the type formula indicated below:
- acetals closely related to methylal, CH 3 OCH 2 OCH 3 , which may be regarded as the parent member of the group in which n of the type formula equals 1. They are synthesized by the action of methanol on aqueous formaldehyde or polyoxymethylene glycols in the presence of an acidic catalyst just as methylal is produced. On hydrolysis they are converted to formaldehyde and methanol. Like other acetals, they possess a high degree of chemical stability. They are not readily hydrolyzed under neutral or alkaline conditions, but are attacked by even relatively dilute acids. They are more stable than the polyoxymethylene diacetates.
- Polyoxymethylene dimethyl ethers are prepared in laboratory scale by heating polyoxymethylene glycols or paraformaldehyde with methanol in the presence ⁇ of a trace of sulfuric or hydrochloric acid in a sealed tube for 15 hours at 150°C, or for a shorter time (12 hours) at 165° to 180°C.
- Considerable pressure is caused by decomposition reactions, which produce carbon oxides, and by formation of some dimethyl ether.
- the average molecular weight of the ether products increases with the ratio of paraformaldehyde or polyoxymethylene to methanol in the charge.
- a high polymer is obtained with a 6 to 1 ratio of formaldehyde (as polymer) to methanol.
- the n value of the type formula CH3 ⁇ (CH2 ⁇ )nCH3 is greater than 100, generally in the range of
- the products are purified by washing with sodium sulfite solution, which does not dissolve the true dimethyl ethers, and may then be fractionated by fractional crystallization from various solvents.
- Crystalline aluminosilicates are the most prevalent and, as described in the patent literature and in the published journals, are designated by letters or other convenient symbols.
- Moulton and David W. Naegeli reported blending a mixture of alkoxy-terminated poly-oxymethylenes, having a varied mixture of molecular weights, with diesel fuel to form an improved fuel for autoignition engines.
- Two mixtures were produced by reacting paraformaldehyde with (i) methanol or (ii) methylal in a closed system for up to 7 hours and at temperatures of 150° to 240°C and pressures of 300 psi to 1,000 psi to form a product containing methoxy-terminated poly-oxymethylenes having a molecular weight of from about 80 to about 350 (polyoxymethylene dimethyl ethers).
- a 1.6 liter cylindrical reactor was loaded with a mixture of methanol and paraformaldehyde, in molar ratio of about 1 mole methanol to 3 moles paraformaldehyde, and in a second preparation, methylal (dimethoxymethane) and paraformaldehyde were combined in a molar ratio of about 1 mole methylal to about 5 moles paraformaldehyde.
- methylal (dimethoxymethane) and paraformaldehyde were combined in a molar ratio of about 1 mole methylal to about 5 moles paraformaldehyde.
- a small amount of formic acid about 0.1 percent by weight of the total reactants, was added as a catalyst.
- the same temperatures, pressures and reaction times are maintained as in the first. Disadvantages of these products include the presence of formic acid and thermal instability of methoxy-terminated poly- oxymethylenes under ambient pressure and acidic conditions.
- the base diesel fuel when blended with such mixtures in a volume ratio of from about 2 to about 5 parts diesel fuel to 1 part of the total mixture, is said to provide a higher- quality fuel having significantly improved lubricity and reduced smoke formation without degradation of the cetane number or smoke formation characteristics as compared to the base diesel fuel.
- This invention is directed to overcoming the problems set forth above in order to provide Diesel fuel having improved qualities. It is desirable to have a method of producing a high quality diesel fuel that has better fuel lubricity than conventional low-sulfur, low-aromatics diesel fuels, yet has comparable ignition quality and smoke generation characteristics. It is also desirable to have a method of producing such fuel which contains an additional blended component that is soluble in diesel fuel and has no carbon-to-carbon bonds. Furthermore, it is desirable to have such a fuel wherein the concentration of gums and other undesirable products is reduced.
- continuous processes of this invention comprise providing a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst, and heating the feedstream with the heterogeneous acidic catalyst under conditions of reaction sufficient to form an effluent of condensation comprising water, methanol and one or more polyoxymethylene dimethyl ethers having a structure represented by the type formula CH3 ⁇ (CH2 ⁇ )nCH3
- n is a number from 1 to about 10.
- Suitable soluble condensation promoting components capable of activating the heterogeneous acidic catalyst comprises at least one member of the group consisting of low boiling, monobasic organic acids, preferable the group consists of formic acid and acetic acid. More preferable soluble condensation promoting component capable of activating the heterogeneous acidic catalyst comprises at least formic acid .
- the heating of the feedstream with the acidic catalyst is carried out at in at least one catalytic distillation column having internal and/or external stages of contact with the acidic catalyst and internal zones to separate methylal from higher polyoxymethylene dimethyl ethers.
- at least a liquid portion of the effluent containing polyoxymethylene dimethyl ethers is contacted with an anion exchange resin disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
- the essentially acid-free mixture of polyoxymethylene dimethyl ethers is fractionated within a section of the distillation column below the stages of contact with the acidic catalyst to provide an aqueous side- stream which is withdrawn from the distillation column, and an essentially water- free mixture of polyoxymethylene dimethyl ethers having values of n greater than 1 which mixture is withdrawn from the distillation column near its bottom.
- a source of methanol can be admixed with the feedstream, and/or into the stages of contact with the acidic catalyst.
- Suitable acidic catalysts include at least one member of the group consisting of bentonites, montmorillonites, cation-exchange resins, and sulfonated fluoroalkylene resin derivatives, preferably comprises a sulfonated tetrafluoroethylene resin derivative.
- a preferred class of acidic catalysts comprises at least one cation-exchange resin of the group consisting- of styrene- divinylbenzene copolymers, acrylic acid-divinylbenzene copolymers, and methacrylic acid-divinylbenzene copolymers.
- the heating of the bottom stream with the acidic catalyst employs at least one distillation column with internal and/or external stages of contact with the acidic catalyst.
- Another aspect this invention is an integrated process which further comprises formation of the feedstream by a process comprising continuously contacting methanol in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, methanol, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture to predominantly condense methanol, and adsorb formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture comprising dihydrogen and carbon monoxide.
- a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, methanol, dihydrogen and carbon monoxide
- cooling the gaseous dehydrogenation mixture to
- the resulting liquid source of formaldehyde contains about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than 5 percent water, and is recovered by using at least one continuous adsorption column with cooling to temperatures in a range downward from about 100°C to 25°C.
- FIGURE 1 to FIGURE 4 are schematic flow diagrams depicting a preferred aspects of the present invention for continuous catalytic production of polyoxymethylene dimethyl ethers by chemical conversion of methanol and formaldehyde in which a feedstream comprising a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is heated with the heterogeneous acidic catalyst in a catalytic distillation column with internal stages of contact.
- a liquid portion of the effluent of condensation, containing polyoxymethylene dimethyl ethers is contacted with an anion exchange resin disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture, and fractionated to provide suitable components for blending into diesel fuel.
- the feedstream in the integrated process depicted in FIGURE 1 is a stream of formaldehyde in methanol derived from dehydrogenation of dimethyl ether.
- FIGURE 2 is a stream of formaldehyde in methanol derived from dehydrogenation of methanol.
- the feedstream in the integrated process depicted in FIGURE 3 is a stream of aqueous formaldehyde in methanol derived from oxidation of dimethyl ether.
- recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether, preheated against reactor product, and then fed to the formaldehyde reactor.
- the feedstream in the integrated process depicted in FIGURE 4 is a stream of aqueous formaldehyde in methanol derived from oxidative dehydrogenation of dimethyl ether.
- recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether, preheated against reactor product, and then fed to the formaldehyde reactor.
- the improved processes of the present invention employ a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst.
- Suitable component ⁇ include any acidic compound soluble in the feedstream, preferably an organic compound soluble in a feedstream of about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than 5 percent water.
- a preferred class of condensation promoting components capable of activating a heterogeneous acidic catalyst includes members of the group consisting of low boiling, monobasic organic acids, more preferably acetic acid or formic acid.
- effluent mixtures can comprise water, methanol, formaldehyde, methylal and other polyoxymethylene dimethyl ethers having a structure represented by the type formula
- n is a number ranging between 1 and about 15, preferably between 1 and about 10. More preferably the mixture contains a plurality of polyoxymethylene dimethyl ethers having values of n are in a range from 2 to about 7.
- Conditions of reaction include temperatures in a range from about 50° to about 300°C, preferably in a range from about 150° to about 250°C.
- Sources of dimethyl ether useful herein are predominantly dimethyl ether, preferably at least about 80 percent dimethyl ether by weight, and more preferably about 90 percent dimethyl ether by weight.
- Suitable dimethyl ether sources may contain other oxygen containing compounds such as alkanol and/or water, preferably not more than about 20 percent methanol and/or water by weight, and more preferably not more than about 15 percent methanol and/or water by weight.
- the ratio of formaldehyde to methanol in the feedstreams is any mole ratio which results in the production of the desired oxygenated organic compound.
- the ratio of formaldehyde to methanol is preferably between about 10: 1 and about 1 : 10 moles.
- the ratio of formaldehyde to methanol is preferably between about 5: 1 and about 1:5 moles. More preferably, the ratio of formaldehyde to methanol is between about 2: 1 and about 1:2 moles.
- the feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is heated in a catalytic distillation column with an acidic catalyst, which is heterogeneous to the feedstream, under conditions of reaction sufficient to convert formaldehyde and methanol present to methylal and higher polyoxymethylene dimethyl ethers.
- the solid acidic catalyst for use in the present invention include cation exchange resins, sulfonated fluoroalkylene resin derivatives, and crystalline aluminosilicates.
- Cation exchange resins that can be used in the present invention may be carboxylated or sulfonated derivatives, but sulfonated derivatives are preferred because of the high reaction yield that can be attained.
- Ion exchange resins that can be used may be gel-type cation exchange resins or macroporous (macroreticular) cation-exchange resins, but the latter as exemplified by Amberlite 200C of Organc Co, Ltd. and Lewalit SP112 of Bayer A.G. are preferred because of the high reaction yield that can be attained.
- useful ion exchange resins include a styrene-divinylbenzene copolymer, an acrylic acid-divinylbenzene copolymer, a methacrylic acid- divinylbenzene copolymer, etc.
- a sulfonated tetrafluoroethylene resin derivative (trade name, Naflon H) is preferably used as a sulfonated fluoroalkylene resin derivative.
- the ratio of formaldehyde to dimethyl ether in the feedstreams is any mole ratio which results in the production of the desired oxygenated organic compound.
- the ratio of formaldehyde to dimethyl ether is preferably between about 10: 1 and about 1:10 moles.
- the ratio of formaldehyde to dimethyl ether is preferably between about 5:1 and about 1 :5 moles. More preferably, the ratio of formaldehyde to dimethyl ether is between about 2: 1 and about 1:2 moles.
- a source of formaldehyde is formed by subjecting methanol in the vapor phase to dehydrogenation in the presence of a catalytically effective amount of a catalyst preferably containing copper and zinc as well as tellurium and/or selenium and/or sulfur, if appropriate in the form of the oxides.
- Oxide catalysts which can contain copper, zinc and tellurium, are particularly useful.
- One class of preferred catalysts comprises copper, zinc and selenium or tellurium as catalyst components in an atomic ratios of 1 :0.01- 0.5:0.005-0.5, preferably 1 :0.05-0.5:0.01-0.4, with the proviso that the amount of zinc is at least equal to the amount of selenium or tellurium present.
- the catalyst used in the present invention may be prepared by any one of conventional procedures known to those skilled in the art, for example, precipitation method, thermal decomposition method, or deposition and drying method. Any of these procedures may be properly selected based on the raw material to be used.
- Suitable raw materials for catalyst useful in the present invention include a copper salt of a mineral acid such as copper nitrate, copper chloride, copper sulfate, copper sulfite, copper hydroxide, copper oxide, basic copper carbonate, metallic copper, and the like as a source of copper; a zinc salt of a mineral acid such as zinc nitrate, zinc chloride, zinc sulfate, zinc sulfite, zinc hydroxide, zinc oxide, metallic zinc and the like as a source of zinc; and selenic acid, selenious acid, selenium oxide, or metallic selenium and the like as a source of selenium.
- zinc selenide, zinc selenate, zinc selenite, and the like may be used as a source of both zinc and selenium
- copper selenide may be used as a source of both copper and selenium.
- Such catalysts can be prepared, for example, by kneading copper oxide with zinc oxide and tellurium dioxide (and/or selenium dioxide and/or ammonium sulfate) in the presence of water, drying the mixture at 130° C. and then pressing it to form pills, with or without admixture of a carrier.
- Suitable raw materials may be formed to a particle having a desired shape which may be tablet, sphere or the like and the average diameter of the particles thus formed should be more than 1 mm, preferably 2 to 5 mm.
- Catalyst particles are then reduced in a reductive atmosphere, for example, in two steps, first at a temperature of 100° to 300°C, preferably 150° to 250°C for more than 0.2 hour, preferably 0.5 to 1 hour and then at the temperature of 500° to 750°C, preferably 600° to 700°C for more than 0.1 hour, preferably 0.5 to 1 hour.
- the copper oxide is completely or partially reduced to metallic copper, during use, by the hydrogen formed on dehydrogenation of methanol.
- the process may be carried out with the catalysts in the form of a fixed bed in the reaction vessel, for example a tubular reactor.
- a fluidized bed can also be used.
- methanol may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
- FIGURE 1 In integrated processes of this invention a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, formic acid, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde and formic acid therein; and separating the resulting liquid source of formaldehyde from a gaseous mixture comprising dihydrogen and carbon monoxide.
- a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous
- a mixture containing dimethyl ether in substantially liquid form is unloaded, for example from a road tanker (not shown), into dimethyl ether storage vessel 12 which supplies charge pump 1 4 through conduit 1 3 .
- Charge pump 1 4 transfers the liquid dimethyl ether through conduit 16 into manifold 92 which is in flow communication with heat exchanger 1 04 and formaldehyde reactor 90 through conduit 94.
- Formaldehyde reactor 90 contains particulate dehydrogenation catalyst disposed in a plurality of tubes of a vertical heat exchanger which is maintained at elevated temperatures by circulation of heating fluid to the shell side of formaldehyde reactor 90 through conduit 88 from furnace 80. Heating fluid is returned to furnace 80 through conduits 96 and 86 by means of pump 84. Natural gas or other suitable fuel is supplied to furnace fuel manifold 82 through conduit 74 from fuel supply 72 . As described below, at least a portion of the co- product hydrogen is used as fuel for combustion with air in furnace 80.
- CuZnTeO/Al2 ⁇ 3 or CuZnSeO/AhOg catalyzes the conversion of dimethyl ether to formaldehyde by a reversible dehydrogenation reaction at temperatures in a range from about 500° to 750°, preferably in a range from about 600° to 700°C:
- Gaseous effluent from formaldehyde reactor 90 is transferred through conduit 102 , cooled against the reactor feedstream in exchanger 104 and then passed through conduit 106 into an adsorption tower 100 where formaldehyde and dimethyl ether are separated from a mixture of gaseous co- products including hydrogen, methane, and oxides of carbon.
- Adsorption tower 100 contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with an adsorption liquid.
- Formaldehyde in methanol from the bottom of the adsorption tower is circulated in a pump-around to a lower section of the tower through conduits 1 12 and 1 1 6 , cooler 120 , and conduit 1 1 8 by means of pump 1 1 4 .
- Methanol is supplied to an upper section of the adsorption separation tower through conduit 122 by means of pump 48.
- Overhead temperatures are in a range of about 15° to about 55°C, preferably about 20° to about 40°C.
- a gaseous overhead stream including hydrogen, methane, and oxides of carbon is transferred through conduit 1 24 and into furnace fuel manifold 82 by means of blower 126.
- additional fuel such as natural gas is supplied to manifold 82 from a suitable fuel source 72 through conduit 74.
- Formaldehyde solution from the adsorption tower is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water.
- effluent from the adsorption tower is a valuable product in itself.
- a portion of the stream can optionally be diverted from adsorption tower 100 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether.
- the stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
- the adsorption liquid containing formaldehyde, formic acid and dimethyl ether in methanol is transferred from adsorption tower 100 through conduits 1 12 and 18 , by means of pump 1 14 , and into ether recovery column 30 , where unreacted dimethyl ether is separated from the effluent stream to form a resulting liquid mixture of formaldehyde, formic acid and methanol.
- a dimethyl ether fraction is taken overhead through conduit 32 and into condenser 34 where a liquid condensate is formed.
- a suitable portion of the liquid condensate is refluxed into column 30 through conduits 35 and 36 while another portion of the condensate is supplied to manifold " 92 through conduit, 37 and 39 by means of pump 38.
- Conduit 28 supplies pump 40 with liquid from the bottom of ether recovery column 30.
- a suitable portion of the liquid stream from the bottom of column 30 is transferred through conduits 41 and 42 , by means of pump 40 , and into reboiler 43 which is in flow communication with the bottom of the column through conduit 44.
- a liquid stream from the bottom of column 30 is transferred through conduit 45 into reactive distillation column 50 , where simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus.
- a stream containing methanol from storage vessel 46 maybe admixed with the feedstream, and/or into the stages of contact with the acidic catalyst of the reactive distillation column 50.
- Charge pump 48 can transfer methanol into the reactive distillation column 50 through conduits 47 and 49.
- Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter- currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
- the overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54.
- a suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56.
- a product stream containing methylal is transferred through conduit 57 to product storage (not shown).
- Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50.
- a suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66.
- a product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown).
- product storage not shown.
- an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
- An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 58.
- FIGURE 2 Still another preferred aspect of the invention is depicted schematically in FIGURE 2.
- a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting methanol in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, formic acid, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde and formic acid therein; and separating the resulting liquid source of formaldehyde from a gaseous mixture comprising dihydrogen and carbon monoxide.
- a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as
- gaseous methanol is dehydrogenated in the presence of catalytically effective amount of a catalyst consisting of copper, zinc and tellurium or selenium as catalyst components.
- a catalyst consisting of copper, zinc and tellurium or selenium as catalyst components.
- FIGURE 2 a mixture containing methanol in substantially liquid form is unloaded, for example from a road tanker (not shown), into methanol storage vessel 46 which supplies charge pump 48 through conduit 47.
- Charge pump 48 transfers the liquid methanol through conduit 42 and conduit 92 which is in flow communication with heat exchanger 104 and formaldehyde reactor 90 through conduit 94.
- Formaldehyde reactor 90 contains particulate dehydrogenation catalyst disposed in a plurality of tubes of a vertical heat exchanger which is maintained at temperatures from about 500° to 750°C by circulation of heating fluid to the shell side of formaldehyde reactor 90 through conduit 88 from furnace 80. Heating fluid is returned to furnace 80 through conduits 96 and 86 by means of pump 84. Natural gas or other suitable fuel is supplied to furnace fuel manifold 82 through conduit 81 from a suitable fuel source 83. As described below, at least a portion of the co-product hydrogen is used as fuel for combustion with air in furnace 80.
- CuZnTeO or CuZnSeO catalyzes the conversion of methanol to formaldehyde by a reversible dehydrogenation reaction at temperatures in a range from about 500° to 750°, preferably in a range from about 600° to 700°C:
- Gaseous effluent from formaldehyde reactor 90 is transferred through conduit 1 02 , cooled against the reactor feedstream in exchanger 104 and then passed through conduit 1 06 into a separation tower 1 00 where formaldehyde and methanol are separated from a mixture of gaseous co-products including hydrogen, methane, and oxides of carbon.
- Adsorption tower 1 00 contains a high efficiency packing or other means for contacting counter- currently the gaseous stream with an adsorption liquid.
- Adsorption liquid from the bottom of adsorption separation tower 1 00 is circulated in a pump-around on the adsorption tower through conduits 1 12 and 1 16 , cooler 120 , and conduit 1 1 8 by means of pump 1 14.
- Methanol is diverted from conduit 42 , through conduit 44 to supply pump 1 14.
- Overhead temperatures in separation tower 100 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C.
- a gaseous overhead stream including hydrogen, methane, and oxides of carbon is transferred through conduit 1 22 and into furnace fuel manifold 82 by means of blower 1 24.
- additional fuel such as natural gas is supplied to manifold 82 through conduit 81 from a suitable fuel source 83 .
- Formaldehyde solution from the adsorption tower is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water. It should be apparent that effluent from the adsorption tower is a valuable product in itself.
- a portion of the stream can optionally be diverted from adsorption tower 1 00 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether.
- the stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
- Adsorption liquid containing formaldehyde, formic acid and water in methanol is transferred from adsorption tower 1 00 through conduits 1 12 and 45 , by means of pump 1 1 4 , and into reactive distillation column 50.
- Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
- the overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54.
- a suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56.
- a product stream containing methylal is transferred through conduit 57 to product storage (not shown).
- Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50.
- a suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66.
- a product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown).
- product storage not shown.
- an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
- An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 58.
- FIGURE 3 Still another preferred aspect of the invention is depicted schematically in FIGURE 3.
- a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of an oxidation promoting catalyst comprising tungsten oxide as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous oxidation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
- a source of formaldehyde is formed by subjecting dimethyl ether in the vapor phase to hydration and oxidation in the_ presence a catalytically effective amount of an oxidation promoting catalyst comprising tungsten oxide as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous mixture to predominantly condense water and adsorb formaldehyde therein; and separating the resulting aqueous source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
- the ratio of dioxygen to total dimethyl ether is, according to the present invention, any mole ratio which results in the production of the desired source of formaldehyde.
- the ratio of dioxygen to ether and, if present, alkanol is preferably between about 1 : 1 and about 1 : 1000 moles. More preferably, the ratio of dioxygen to dimethyl ether is between about 1 : 1 and about 1 : 100 moles. Most preferably, the ratio of dioxygen to dimethyl ether is between about 1 : 1 and about 1 : 10 moles.
- Air 99 mol percent to 82.6 mol percent Reaction temperature: 200° to 450°C
- Dimethyl ether 3 mol percent to 12 mol percent Reaction temperature: 250° to 400°C.
- the dioxygen can be added to the reaction mixture as pure molecular oxygen, or diluted with an inert gas such as nitrogen or argon. It is preferred to keep the dioxygen at no more than 10 mole percent of the entire reaction feed so as 4o avoid the formation of explosive mixtures.
- dimethyl ether is oxidized with a source of dioxygen in the presence of an oxidation-promoting catalytic composition containing, as an essential ingredient, a metal oxide with or without up to about 10 percent of a supplemental inorganic compound based upon the total weight of metal oxide and supplemental inorganic compounds
- Suitable metal oxide catalysts have been developed for reacting dimethyl ether with a source of dioxygen to produce formaldehyde, as described in U.S. Patent Number 3,655,771, or U.S. Patent Number 4,753,916.
- Well known methods of preparing suitable tungsten oxide include adding to ammonium tungstate concentrated hydrochloric or nitric acid, to precipitate the oxide.
- Oxide is molded into tablets or supported on inert carriers, such as alumina, Carborundum, pumice or the like.
- vanadium oxide, boron oxide, molybdenum oxide, phosphoric acid, an ammonium salt thereof, ammonium chloride or the like is added to tungsten oxide in an amount of not more than 10%, in order to maintain the activity of tungsten oxide at the original level and to obtain a catalyst having a sufficient mechanical strength to withstand operating conditions during its useful catalytic life.
- the addition thereof results in the combination with tungsten oxide and consequently the aggregatability of powdered tungsten oxide is enhanced, molding of the oxide is facilitated and the oxide is hardened.
- tungsten oxide powder produced by any generally known method
- the resulting mixture is milled well with water into a paste.
- This paste is dried, ground into 12 mesh, size- controlled and shaped into tablets by a tablet-forming machine. These tablets are sufficiently dried, and thereafter calcined in air at 500°C for 7 to 8 hours to obtain very hard tablets.
- the present invention further provides a method for selective oxidation of dimethyl ether to formaldehyde in the presence of an catalytically effective amount of a composition of matter comprising ⁇ - Mo(i - x )W x O3, where x is a number between 0 and 1, preferably where x is a number between 0 and 0.5, and more preferably where x is 0 or a number between 0 and 0.1.
- a composition of matter comprising ⁇ - Mo(i - x )W x O3, where x is a number between 0 and 1, preferably where x is a number between 0 and 0.5, and more preferably where x is 0 or a number between 0 and 0.1.
- the selective oxidation of dimethyl ether to formaldehyde is conducted at temperatures in a range from about 200° to about 450°C, and more preferably in a range from about 250° to about 400°C.
- Preferred operating pressures are from about 1 to about
- One method for preparation of a composition comprising ⁇ - M ⁇ ( i- ⁇ )W x O 3 , comprises spray-drying a solution of molybdic acid or molybdic and tungstic acids in appropriate concentrations and heating the resulting powder at a temperature of from about 275° to about 450° C.
- Another method comprises sputtering a molybdenum or mixed metal oxide target in appropriate concentrations onto a thermally floating substrate in an atmosphere comprising oxygen and an inert gas wherein the oxygen is in an amount from about 5 to about 50 volume percent.
- Most preferred compositions comprising ⁇ - M ⁇ (i- x )W x ⁇ 3 are where x is 0 or a number between 0 and 0.05.
- This phase of the specified metal or mixed metal oxide has a distorted three dimensional RCO 3 structure based on corner-linked octahedra.
- the thermal stability of the beta phase of M0O 3 can be improved by tungsten substitution as evidenced by the beta to alpha transformation temperature of about 530°C of Moo .95 Wxo .05 Q 3 , compared to about 450°C of Mo ⁇ 3.
- compositions comprising the "beta" phase of the specified metal and mixed metal oxides ( ⁇ - M ⁇ (i- x )W x O3) can be prepared in films by sputtering or spin coating.
- dimethyl ether may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
- a mixture containing dimethyl ether in substantially liquid form is supplied from dimethyl ether storage vessel 12 to pump 1 4 through conduit 13 , and into feed manifold 92 through conduit 1 5.
- a recycle stream of wet gas is transferred into feed manifold 92 through conduit 98 .
- a gaseous stream containing dioxygen and dinitrogen from a source (not shown) is supplied to compressor 94 through conduit 93 .
- Compressed gas is transferred through conduit 95 , combined in feed manifold 92 with the recycle stream of wet gas from the formaldehyde adsorber and the dimethyl ether.
- the resulting feed mixture is heated against reactor effluent in heat exchanger 76 , and transferred into oxidation reactor 90 through conduit 91 .
- Oxidation reactor 90 is a vertical heat exchanger.
- the tubes are filled with catalyst pellets. (The upper and lower regions of the tubes contain pellets of inert material.)
- a portion of heat generated in the catalyst bed is diverted to steam generation within oxidation reactor 90 thereby providing cooling of effluent from the bed (not shown).
- a thermal fluid is vaporized on the shell side and circulated to a steam generator to generate steam at pressures of up to 300 psig.
- an oxidation-promoting catalyst preferably consisting essentially of a metal oxide component with or without a supplemental inorganic compound.
- tungsten oxide catalysts are used because they give almost complete oxidation to formaldehyde at much lower temperatures than are required for the silver-catalyzed dehydrogenation reaction.
- Gaseous effluent from oxidation reactor 90 is transferred through conduit 96 , cooled against the reactor feedstream in exchanger 76 and then passed through conduit 97 into spray column 1 00 where a solution of aqueous formaldehyde in methanol is formed.
- Formaldehyde solution from the bottom of spray column 1 00 at temperatures in a range downward from about 100°C to about 75°C, is supplied to pump 1 04 through conduit 103 .
- Formaldehyde solution from the spray column is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water and less than 350 ppm of formic acid.
- a portion of the stream can optionally be diverted from adsorption tower 100 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether.
- the stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
- the formaldehyde solution from pump 1 04 is combined with a solution of formaldehyde in methanol supplied from the bottom of adsorption column 1 10 through conduits 1 13 and 108 , by means of pump 1 14.
- the combination forms a stream which is circulated to the top of spray column 100 through conduit 106. It is important to maintain the temperature of the pump- around stream above about 70°C to prevent paraformaldehyde formation.
- a portion of the cooling required in spray column 100 may be obtained by including a heat exchanger in the flow through conduit 1 06.
- a gaseous overhead stream from spray column 100 is transferred through conduit 102 into adsorption column 1 1 0 , which contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with aqueous adsorption liquid.
- a solution of formaldehyde in methanol from the bottom of adsorption column 1 10 is circulated in a pump- around to a lower section of the column through conduits 1 13 and 1 1 5 , cooler 1 1 6 , and conduit 1 1 7 by means of rjump 1 14 .
- methanol for the adsorption is supplied to a section of adsorption column 1 10 by means of pump 48 through conduit 125 , cooler 126 , and conduit 128 . Further up the column, pump-arounds may be cooled to successively lower temperatures. In some configurations, the lower pump- around stream is not cooled at all.
- a vapor side draw from adsorption column 1 1 0 is transferred through conduit 1 12 and mixed with fresh air as previously described.
- the adsorber overhead passes through conduit 1 1 8 into condenser 122 .
- An appropriate amount of condensate is formed and refluxed to the top section of the adsorber column through conduit 124.
- Overhead temperatures in adsorption column 1 1 0 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C. Gases are vented from condenser 122 through conduit 120 to disposal, typically, in a thermal oxidation unit (not shown).
- the absorber overhead which contains trace amounts of formaldehyde (about 10-30 ppm), is treated in several ways by catalytic or thermal converter to oxidize hydrocarbons and recuperative heat exchange. Typically, 170 psig to 200 psig steam is generated to improve overall economics of preferred embodiments of the invention.
- a portion of the solution of formaldehyde in methanol is diverted from pump 1 04 into reactive distillation column 50 through conduit 45.
- reactive distillation column 50 simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus.
- a stream containing methanol from storage vessel 46 may by fed into the reactive distillation column 50.
- Charge pump 48 transfers methanol in substantially liquid form into the reactive distillation column 50 through conduits 47 and 49.
- Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
- the overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54.
- a suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56.
- a product stream containing methylal is transferred through conduit 58 to product storage (not shown).
- Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50.
- a suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66.
- a product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown).
- product storage not shown.
- an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
- An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 72.
- the side stream from column 50 is transferred by means of pump 74 through conduit 75 to waste disposal (not shown).
- tungsten oxide catalyzes the conversion of dimethyl ether to formaldehyde by an oxidation reaction at temperatures in a range from about 350° to about 600°C , preferably in a range from about 400° to about
- FIGURE 4 Still another preferred aspect of the invention is depicted schematically in FIGURE 4.
- a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of an oxidative dehydrogenation promoting catalyst comprising silver as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, methanol, dioxygen, diluent gas, carbon dioxide and water vapor; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
- recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether,
- dimethyl ether is oxidized with a source of dioxygen in the presence of an oxy-dehydrogenation catalytic composition containing, as an essential ingredient, .silver with or without up to about 10 percent of a supplemental inorganic compound based upon the total weight of metal oxide and supplemental inorganic compounds.
- Suitable oxy- dehydrogenation catalysts have been developed for converting methanol with a source of dioxygen to produce formaldehyde, as described in U.S. Patent Number 5,401 ,884, U.S. Patent
- the starting materials are fed through a silver-containing fixed-bed catalyst installed in a vertical tubular reactor.
- the catalyst preferably comprises silver crystals having a particle size of from 0.1 to 3 mm, in particular from 0.2 to 2.5 mm.
- the fixed- bed catalyst can have a multi-layer structure through arrangement of the silver crystals in layers of different particle size.
- the starting mixture of dimethyl ehter vapor, oxygen- containing gas, and, if used, steam and inert gas is preferably passed through the tubular reactor from top to bottom.
- the process is carried out in one step by passing the starting mixture through the fixed catalyst bed at from 550° to 750°C, in particular from 600° to 720°C, particularly advantageously at from 660° to 700°C.
- the process is preferably carried out continuously at from 0.5 to 3 bar, in particular at from 0.8 to 2 bar, preferably at from 1 to 1.5 bar.
- the residence times in the catalyst zone are from 0.001 to 1 second, preferably from 0.002 to 0.1 second.
- the reaction gases leaving the catalyst zone are advantageously cooled within a short time, for example to below 350°C.
- the cooled gas mixture can expediently be fed to an adsorption tower, in which the formaldehyde is washed out of the gas mixture by means of water.
- dimethyl ether may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
- a mixture containing dimethyl ether in substantially liquid form is supplied from dimethyl ether storage vessel 12 to pump 1 4 through conduit 13.
- Dimethyl ether is transferred through conduit 1 6 into feed manifold 92 .
- a recycle stream of wet gas is transferred into feed manifold 92 by means of blower 88.
- a gaseous stream containing dioxygen and dinitrogen from a source (not shown) is supplied to compressor 94 through conduit 93 .
- Compressed gas is transferred through conduit 95 , combined in feed manifold 92 with the recycle stream of wet gas from the formaldehyde adsorber and the dimethyl ether.
- the resulting mixture is heated against reactor effluent in heat exchanger 80 , and transferred into oxidation reactor 90 through conduit 82 and feed manifold 84
- Formaldehyde reactor 90 contains an oxidative dehydrogenation catalyst disposed in a thin layer directly above a vertical heat exchanger where effluent from the catalyst layer is promptly cooled.
- Boiler feed water at about 110° to 130°C is supplied through conduit 85 to the heat exchanger for generation of low pressure steam in the lower section of the formaldehyde reactor.
- the steam is transferred through conduit 86 , mixed with the preheated mixture of dimethyl ether, wet recycle gas and air stream in feed manifold 84 , and transferred into formaldehyde reactor 90. Steam is metered into the preheated methanol-air mixture to control the reactor outlet temperature.
- the mole ratio of fresh air feed to methanol is between 0.5 and 2.0, preferably about 1.25 and typically the mole ratio of dimethyl ether to steam is about 3.
- the pressure is only slightly above atmospheric. Since the catalyst layers are less than one inch in thickness, the pressure drop is negligible.
- metallic silver catalyzes the conversion of dimethyl ether to formaldehyde by a reversible dehydrogenation reaction at temperatures from about 500° to 700°C:
- the oxidative dehydrogenation catalyst is generally silver crystals supported on a stainless steel mesh, or a shallow bed of silver crystals, spherical particles, or granules.
- the reaction is endothermic, and theoretical equilibrium is approximately 50 percent yield at 400°C, 90 percent at 500°C, and 99 percent at 700°C.
- a portion of the hydrogen formed is oxidized to water. Formation of water is exothermic and provides heat to maintain the endothermic hydrogenation reaction. Heat is also provided by the direct oxidation of methanol:
- Methanol conversion in the reactor is typically between 65 percent and 80 percent, depending largely on the amount of steam introduced at the methanol vaporization step.
- Formaldehyde is lost by several side reactions, including those producing co-products including carbon monoxide, carbon dioxide, methane, formic acid, and methyl formate.
- Gaseous effluent from oxidation reactor 90 is transferred through conduit 96 , cooled against the reactor feedstream in exchanger 80 and then passed to an absorption system, where aqueous formaldehyde is absorbed in methanol.
- the effluent gases flow through conduit 98 into spray column 100 where a solution of formaldehyde is formed.
- Formaldehyde solution from the bottom of spray column 1 00 at temperatures in a range downward from about 100°C to about 75°C, is supplied to pump 104 through conduit 103.
- a portion of the aqueous formaldehyde is transferred through conduit 45 into reactive distillation column 50.
- Formaldehyde solution from the spray column is generally about 55 percent by weight formaldehyde, about 43 methanol weight percent about 2 weight percent water and less than 350 ppm of formic acid.
- a portion of the stream can optionally be diverted from adsorption tower 1 00 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether.
- the stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
- Formaldehyde solution is combined with a solution of formaldehyde supplied from the bottom of adsorption column 1 10 through conduits 1 13 and 108 , by means of pump 1 14 , and circulated to the top of spray column 100 through conduit 1 06 . It is important to maintain the temperature of the pump-around stream above about 70°C to prevent paraformaldehyde formation.
- a portion of the cooling required in spray column 1 00 may be obtained by including a heat exchanger in the flow through conduit 1 06 .
- a gaseous overhead stream from spray column 1 00 is transferred through conduit 1 02 into adsorption column 1 10 , which contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with aqueous adsorption liquid.
- a dilute aqueous formaldehyde from the bottom of adsorption column 1 10 is circulated in a pump-around to the bottom section of the column through conduits 1 13 and 1 15 , cooler 1 16 , and conduit 1 17 by means of pump 1 14.
- a liquid side stream is supplied to pump 124 through conduit 125 , transferred through manifold 127 , cooled in cooler 126 , and returned to adsorption column 1 10 through conduit 128 .
- the lower pump-around stream is not cooled at all.
- Caustic solution may be added to the chilled water to improve absorber performance, but it leaves traces of sodium as a contaminant in the product.
- a vapor side draw from adsorption column 1 1 0 is transferred through conduit 1 1 2 and mixed with fresh air as previously described.
- the adsorber overhead passes through conduit 1 1 8 into condenser 122 .
- An appropriate amount of condensate is formed and refluxed to the top section of the adsorber column through conduit 123 .
- Overhead temperatures in adsorption column 1 10 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C. Gases are vented from condenser 122 through conduit 120 to disposal, typically, in a thermal oxidation unit (not shown).
- the absorber overhead which contains trace amounts of formaldehyde (about 10-30 ppm), is treated in several ways by catalytic or thermal converter to oxidize hydrocarbons and recuperative heat exchange. Typically, 170 psig to 200 psig steam is generated to improve overall economics of preferred embodiments of the invention.
- a portion of the solution of formaldehyde in methanol is diverted from pump 104 into reactive distillation column 50 through conduit 45.
- reactive distillation column 50 simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus.
- a stream containing methanol from storage vessel 46 may by fed into the reactive distillation column 50.
- Charge pump 48 transfers methanol in substantially liquid form into the reactive distillation column 50 through conduits 47 and 49.
- Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
- the overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54.
- a suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduit 56.
- a product stream containing methylal is transferred through conduit 58 to product storage (not shown).
- Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50.
- a suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66.
- a product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown).
- an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
- An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 72.
- a catalyst of copper, zinc and selenium was used at several elevated temperatures to convert a liquid feedstream of aqueous methanol and a gaseous feedstream of dimethyl ether, nitrogen and dihydrogen.
- Effluent of the fixed bed reactor was a gaseous dehydrogenation mixture including formaldehyde, dimethyl ether, dihydrogen and carbon monoxide.
- a tubular quartz reactor was charged with 9.27 grams (5 cc) of the CuZnSe particles which had been sieved to 18-40 mesh.
- the tubular quartz reactor (approx. 10 mm inside diameter) was equipped with a quartz thermowell terminating at about the midpoint of the catalyst bed.
- a liquid feed solution was prepared using 13.06 grams of water and 17.33 grams of methanol. The resulting solution was fed by a syringe pump into a preheat zone above the catalyst bed. Using mass flow controllers, a gaseous feedstream of 26.9 percent by volume dimethyl ether, 6.62 volume percent nitrogen and a balance of dihydrogen was also fed to the top of the reactor.
- Liquid products from the reactor were collected in a cool
- a silver catalyst in the form of needles was used at several elevated temperatures to provide a source of formaldehyde by oxidative dehydrogenation of dimethyl ether, steam and methanol.
- a tubular quartz reactor was charged with 3.83 grams (1 cc) of the silver needles.
- the tubular quartz reactor (approx. 10 mm inside diameter) was equipped with a quartz thermowell terminating at about the midpoint of the catalyst bed. Quartz wool was placed above the catalyst zone to assist in vaporizing liquid feed.
- the liquid feed solution containing 18.6 percent methanol and 81.4 percent by weight water was fed by a syringe pump into the preheat zone above the catalyst bed.
- a silver catalyst in the form of needles was used at several elevated temperatures to provide a source of formaldehyde by nonoxidative dehydrogenation of dimethyl ether and steam.
- the liquid feed of water was fed by a syringe pump into the preheat zone above the catalyst bed.
- a gaseous feedstream of 89.1 percent by volume dimethyl ether and 10.9 volume percent nitrogen was also fed to the top of the reactor.
- Samples were collected while temperature of the catalyst bed was controlled to temperatures in a range from about 400° to about 650°C. Operating conditions and results are summarized in Table V.
- substantially is defined as occurring with sufficient frequency or being present in such proportions as to measurably affect macroscopic properties of an associated compound or system. Where the frequency or proportion for such impact is not clear, substantially is to be regarded as about twenty per cent or more.
- the term “essentially” is defined as absolutely except that small variations which have no more than a negligible effect on macroscopic qualities and final outcome are permitted, typically up to about one percent.
- HPE is higher polyoxymethylene dimethyl ethers which are CH3 ⁇ (CH2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
- HPE is higher polyoxymethylene dimethyl ethers which are CH 3 ⁇ (CH 2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
- HPE is higher polyoxymethylene dimethyl ethers which are CH3 ⁇ (CH2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
- HPE is higher polyoxymethylene dimethyl ethers which are CH3 ⁇ (CH2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
- HPE is higher polyoxymethylene dimethyl ethers which are CH 3 ⁇ (CH 2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
- HPE is higher polyoxymethylene dimethyl ethers which are CH3 ⁇ (CH2 ⁇ )nCH3 having n greater than 1
- MeO is methoxy moiety
- DME is dimethyl ether.
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- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
A particularly useful process which includes the steps of providing a feedstream comprising methanol, a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst and a source of formaldehyde; and heating this feedstream with the heterogeneous acidic catalyst in a catalytic distillation column to convert methanol and formaldehyde present to methylal and higher polyoxymethylene dimethyl ethers and to separate the methylal from the higher polyoxymethylene dimethyl ethers is disclosed. Advantageously, methylal and higher polyoxymethylene dimethyl ethers are formed and separated in a catalytic distillation column. By including within the column a section containing an anion exchange resin, an essentially acid-free product is obtained. Products can be used directly as a blending component, or fractionated, as by further distillation, to provide more suitable components for blending into diesel fuel.
Description
PREPARATION OF POLYOXYMF-THYLENE DIMETHYL ETHERS
BY ACLD- ACTIVATED CATALYTIC CONVERSION OF
METHANOL WITH FORMALDEHYDE
TECHNICAL FIELD
The present invention relates to production of organic compounds, particularly polyoxymethylene dimethyl ethers, which are suitable components for blending into fuel having improved qualities for use in diesel engines. More specifically, it relates to providing a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst, and heating this feedstream with the heterogeneous acidic catalyst in a catalytic distillation column to convert methanol and formaldehyde present to methylal and higher polyoxymethylene dimethyl ethers and separate the methylal from the higher polyoxymethylene dimethyl ethers. Advantageously, the catalytic distillation column has a section containing an anion exchange resin whereby an essentially acid-free product is obtained which can be used directly as a blending component, or fractionated, as by further distillation, to provide more suitable components for blending into diesel fuel.
Integrated processes of the invention also provide their own source of formaldehyde. Advantageously, the source of formaldehyde is an un-purified liquid stream derived from a mixture formed by oxidative dehydrogenation (oxy- dehydrogenation) of methanol, dimethyl ether and mixtures thereof using, for example, a catalyst based silver.
BACKGROUND OF THE INVENTION
Conversion of low molecular weight alkanes such as methane to synthetic fuels or chemicals has received increasing attention because low molecular weight alkanes are generally available from secure and reliable sources. For example, natural gas wells and oil wells currently produce vast quantities of
methane. Reported methods for converting low molecular weight alkanes to more easily transportable liquid fuels and chemical feedstocks can be conveniently categorized as direct oxidative routes and/or as indirect syngas routes. Direct oxidative routes convert lower alkanes to products such as methanol, gasoline, and relatively higher molecular weight alkanes. In contrast, indirect syngas routes typically involve production of synthesis gas as an intermediate product.
Routes are known for converting methane to dimethyl ether. For example, methane is steam reformed to produce synthesis gas. Thereafter, dimethyl ether and methanol can be manufactured simultaneously from the synthesis gas, as described in U.S. Patent No. 4,341 ,069 issued to Bell et al. They recommend a dimethyl ether synthesis catalyst having copper, zinc, and chromium co-precipitated on a gamma-alumina base.
Alternatively, methane is converted to methanol, and dimethyl ether is subsequently manufactured from methanol by passing a mixed vapor containing methanol and water over an alumina catalyst, as described in an article by Hutchings in New Scientist (3 July 1986) 35.
Formaldehyde is a very important intermediate compound in the chemical industry. The extreme reactivity of the formaldehyde carbonyl group and the nature of the molecule as a basic building block has made formaldehyde an important feedstock for a wide variety of industrially important chemical compounds. Historically, formaldehyde has found its largest volume of application in the manufacture of phenol - formaldehyde resins, urea-formaldehyde resins and other polymers. Pure formaldehyde is quite uncommon since it polymerizes readily. It was usually obtained as an aqueous solution such as formalin, which contains only about 40 percent formaldehyde. However, more recently, formaldehyde is usually transported as an item of commerce in concentrations of 37 to 50 percent by weight. A solid source of formaldehyde called paraformaldehyde is also commercially available.
Because of the reactivity of formaldehyde, its handling and separation require special attention. It is a gas above -19°C and is flammable or explosive in air at concentrations of about 7 to about 12 mol percent. Formaldehyde polymerizes with itself at temperatures below 100°C and more rapidly when water vapor or impurities are present. Since formaldehyde is usually transported in aqueous solutions of 50 percent by weight or lower concentration, producers have tended to locate close to markets and to ship the methanol raw material, which has a smaller volume.
It is known that some reactions may be carried out by means of catalytic distillation. In catalytic distillation, reaction and separation are carried out simultaneously in a distillation column with internal and/or external stages of contact with catalyst.
In U.S. Pat. No. 4,215,011, Smith, Jr. discloses a method for the separation of an isoolefin, preferably having four to six carbon atoms, from streams containing mixtures thereof with the corresponding normal olefm, wherein the mixture is fed into a reaction-distillation column containing a fixed-bed, acidic cation exchange resin and contacted with the acidic cation exchange resin to react the isoolefin with itself to form a dimer and the dimer is separated from the normal olefin, the particulate catalytic material, i.e., the acidic cation exchange resin, being contained in a plurality of closed cloth pockets, which pockets are arranged and supported in the column by wire mesh.
In U.S. Pat. No. 4,443,559, Smith, Jr. discloses a catalytic distillation structure which comprises a catalyst component associated intimately with or surrounded by a resilient component, which component is comprised of at least 70 vol. percent open space for providing a matrix of substantially open space. Examples of such resilient component are open-mesh, knitted, stainless wire (demister wire or an expanded aluminum); open-mesh, knitted, polymeric filaments of nylon, Teflon, etc.;
and highly-open structure foamed material (reticulated polyurethane).
In U.S. Pat. No. 5,113,015, David A. Palmer, K. D. Hansen and K. A. Fjare disclose to a process for recovering acetic acid from methyl acetate wherein the methyl acetate is hydrolyzed to methanol and acetic acid via catalytic distillation.
In German Democratic Republic DD 245 868 Al published May 20, 1987 in the text submitted by the applicant, preparation of methylal is carried out by reaction of methanol with trioxane, formalin or paraformaldehyde in the presence of a specific zeolite. Autoclave reactions of 1 to 8 hours are described using a zeolite of the "LZ40 type" with a ratio of silicon dioxide to alumina ratio of 78 at temperatures from 493 to 543 K. Methylal content of the product as high as 99.8 percent (without methanol) is reported for trioxane at 523 K for 3 hours. Reaction pressures did not exceed 5 MPa in the autoclave. Neither conversions nor selectivity are reported.
In U.S. Pat. No. 4,967,014, Junzo Masamoto, Junzo Ohtake and Mamoru Kawamura describe a process for formaldehyde production by reacting methanol with formaldehyde to form methylal, CH3OCH2CCH3, and then oxidizing the resulting methylal to obtain formaldehyde. In the methylal formation step, a solution containing methanol, formaldehyde and water was brought into solid-liquid contact with a solid acid catalyst, and a methylal-rich component was recovered as a distillate. This process employs reactive distillation performed using a distillation column and multireaction units. The middle portion of the distillation column was furnished with stages from which the liquid components were withdrawn and pumped to the reactor units, which contained solid acid catalyst. The reactive solutions containing the resulting methylal were fed to the distillation column, where methylal was distilled as the overhead product.
Polyoxymethylene dimethyl ethers are the best known members of the dialkyl ether polymers of formaldehyde. While diethyl and dipropyl polyoxymethylene ethers have been
prepared, major attention has been given to the dimethyl ether polymers. Polyoxymethylene dimethyl ethers make up a homologous series of polyoxymethylene glycol derivatives having the structure represented by use of the type formula indicated below:
CH3θ(CH2θ)n CH3
Chemically, they are acetals closely related to methylal, CH3OCH2OCH3, which may be regarded as the parent member of the group in which n of the type formula equals 1. They are synthesized by the action of methanol on aqueous formaldehyde or polyoxymethylene glycols in the presence of an acidic catalyst just as methylal is produced. On hydrolysis they are converted to formaldehyde and methanol. Like other acetals, they possess a high degree of chemical stability. They are not readily hydrolyzed under neutral or alkaline conditions, but are attacked by even relatively dilute acids. They are more stable than the polyoxymethylene diacetates.
Due to the relatively small differences in the physical properties (melting points, boiling points, and solubility) of adjacent members in this series, individual homologs are not readily separated. However, fractions having various average molecular weight values have been isolated. The normal boiling point temperature of a fraction having average n of 2 in the type formula is reported as 91° to 93°C. Boiling points at atmospheric pressure calculated from partial pressure equations range from 105.0°C for n of 2, to 242.3°C for n of 5. (Walker, Joseph Frederic, "Formaldehyde", Robert E. Krieger Publishing Co., issued as No. 159 of American Chemical Society Monograph series ( 1975), pages 167- 169)
Polyoxymethylene dimethyl ethers are prepared in laboratory scale by heating polyoxymethylene glycols or paraformaldehyde with methanol in the presence ~of a trace of sulfuric or hydrochloric acid in a sealed tube for 15 hours at 150°C, or for a shorter time (12 hours) at 165° to 180°C. Considerable pressure is caused by decomposition reactions,
which produce carbon oxides, and by formation of some dimethyl ether. The average molecular weight of the ether products increases with the ratio of paraformaldehyde or polyoxymethylene to methanol in the charge. A high polymer is obtained with a 6 to 1 ratio of formaldehyde (as polymer) to methanol. In these polymers, the n value of the type formula CH3θ(CH2θ)nCH3 is greater than 100, generally in the range of
300 to 500. The products are purified by washing with sodium sulfite solution, which does not dissolve the true dimethyl ethers, and may then be fractionated by fractional crystallization from various solvents.
U.S. Patent No. 2,449,469 in the names of W. F. Gresham and R. E. Brooks reported obtaining good yields of polyoxymethylene dimethyl ethers containing 2 to 4 formaldehyde units per molecule. This procedure is carried out by heating methylal with paraformaldehyde or concentrated formaldehyde solutions in the presence of sulfuric acid.
In the past, various molecular sieve compositions, natural and synthetic, have been found to be useful for a number of hydrocarbon conversion reactions. Among these are alkylation, aromatization, dehydrogenation and isomerization. Among the sieves which have been used are Type A, X, Y and those of the MFI crystal structure as shown in "Atlas of Zeolite Structure Types," Second Revised Edition, 1987, published on behalf of the Structure Commission of the International Zeolite Associates and incorporated by reference herein. Representative of the last group are ZSM-5 and AMS borosilicate molecular sieves.
Prior art developments have resulted in the formation of many synthetic crystalline materials. Crystalline aluminosilicates are the most prevalent and, as described in the patent literature and in the published journals, are designated by letters or other convenient symbols. Exemplary of these materials _are Zeolite A (Milton, in U.S. Patent No. 2,882,243), Zeolite X (Milton, in U.S. Pat. No. 2,882,244), Zeolite Y (Breck, in U.S. Patent No. 3,130,007), Zeolite ZSM-5 (Argauer, et al., in U.S. Patent No.
3,702,886), Zeolite ZSM-11 (Chu, in U.S. Patent No. 3,709,979), Zeolite ZSM-12 (Rosinski, et al., in U.S. Patent No. 3,832,449), and others.
It is well known that internal combustion engines have revolutionized transportation following their invention during the last decades of the 19th century. While others, including Benz and Gottleib Wilhelm Daimler, invented and developed engines using electric ignition of fuel such as gasoline, Rudolf C. K. Diesel invented and built the engine named for him which employs compression for autoignition of the fuel in order to utilize low- cost organic fuels. Development of improved diesel engines for use in automobiles has proceeded hand-in-hand with improvements in diesel fuel compositions, which today are typically derived from petroleum. Modern high performance diesel engines demand ever more advanced specification of fuel compositions, but cost remains an important consideration.
Even in newer, high performance diesel engines combustion of conventional fuel produces smoke in the exhaust. Oxygenated compounds and compounds containing few or no carbon-to- carbon chemical bonds, such as methanol and dimethyl ether, are known to reduce smoke and engine exhaust emissions. However, most such compounds have high vapor pressure and/or are nearly insoluble in diesel fuel, and they have poor ignition quality, as indicated by their cetane numbers. Furthermore, other methods of improving diesel fuels by chemical hydrogenation to reduce their sulfur and aromatics contents, also causes a reduction in fuel lubricity. Diesel fuels of low lubricity may cause excessive wear of fuel injectors and other moving parts which come in contact with the fuel under high pressures.
Recently, U.S. Patent No. 5,746,785 in the names of David S.
Moulton and David W. Naegeli reported blending a mixture of alkoxy-terminated poly-oxymethylenes, having a varied mixture of molecular weights, with diesel fuel to form an improved fuel for autoignition engines. Two mixtures were produced by reacting paraformaldehyde with (i) methanol or (ii) methylal in a
closed system for up to 7 hours and at temperatures of 150° to 240°C and pressures of 300 psi to 1,000 psi to form a product containing methoxy-terminated poly-oxymethylenes having a molecular weight of from about 80 to about 350 (polyoxymethylene dimethyl ethers). More specifically, a 1.6 liter cylindrical reactor was loaded with a mixture of methanol and paraformaldehyde, in molar ratio of about 1 mole methanol to 3 moles paraformaldehyde, and in a second preparation, methylal (dimethoxymethane) and paraformaldehyde were combined in a molar ratio of about 1 mole methylal to about 5 moles paraformaldehyde. In the second procedure, a small amount of formic acid, about 0.1 percent by weight of the total reactants, was added as a catalyst. The same temperatures, pressures and reaction times are maintained as in the first. Disadvantages of these products include the presence of formic acid and thermal instability of methoxy-terminated poly- oxymethylenes under ambient pressure and acidic conditions.
There is, therefore, a present need for catalytic processes to prepare oxygenated organic compounds, particularly polyoxymethylene dimethyl ethers, which do not have the above disadvantages. An improved process should be carried out advantageously in the liquid phase using a suitable condensation- promoting catalyst system, preferably a molecular sieve based catalyst which provides improved conversion and yield. Such an improved process which converts lower value compounds to higher polyoxymethylene dimethyl ethers would be particularly advantageous. Dimethyl ether is, for example, less expensive to produce than methanol on a methanol equivalent basis, and its condensation to polyoxymethylene dimethyl ethers does not produce water as a co-product.
The base diesel fuel, when blended with such mixtures in a volume ratio of from about 2 to about 5 parts diesel fuel to 1 part of the total mixture, is said to provide a higher- quality fuel having significantly improved lubricity and reduced smoke formation without degradation of the cetane number or smoke formation characteristics as compared to the base diesel fuel.
This invention is directed to overcoming the problems set forth above in order to provide Diesel fuel having improved qualities. It is desirable to have a method of producing a high quality diesel fuel that has better fuel lubricity than conventional low-sulfur, low-aromatics diesel fuels, yet has comparable ignition quality and smoke generation characteristics. It is also desirable to have a method of producing such fuel which contains an additional blended component that is soluble in diesel fuel and has no carbon-to-carbon bonds. Furthermore, it is desirable to have such a fuel wherein the concentration of gums and other undesirable products is reduced.
SUMMARY OF THE INVENTION
Economical processes are disclosed for production of a mixture of oxygenated organic compounds which are suitable components for blending into fuel having improved qualities for use in compression ignition internal combustion engines (diesel engines).
According to the present invention, there is now provided a continuous process for catalytic production of oxygenated organic compounds, particularly polyoxymethylene dimethyl ethers. More specifically, continuous processes of this invention comprise providing a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst, and heating the feedstream with the heterogeneous acidic catalyst under conditions of reaction sufficient to form an effluent of condensation comprising water, methanol and one or more polyoxymethylene dimethyl ethers having a structure represented by the type formula CH3θ(CH2θ)nCH3
in which formula n is a number from 1 to about 10. Advantageously, at least a liquid of the effluent containing polyoxymethylene dimethyl ethers is contacted with an anion- exchange resin to form an essentially acid-free mixture.
Suitable soluble condensation promoting components capable of activating the heterogeneous acidic catalyst comprises at least one member of the group consisting of low boiling, monobasic organic acids, preferable the group consists of formic acid and acetic acid. More preferable soluble condensation promoting component capable of activating the heterogeneous acidic catalyst comprises at least formic acid .
Preferably, the heating of the feedstream with the acidic catalyst is carried out at in at least one catalytic distillation column having internal and/or external stages of contact with the acidic catalyst and internal zones to separate methylal from higher polyoxymethylene dimethyl ethers. In a preferred embodiment of the invention at least a liquid portion of the effluent containing polyoxymethylene dimethyl ethers is contacted with an anion exchange resin disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture. Advantageously, the essentially acid-free mixture of polyoxymethylene dimethyl ethers is fractionated within a section of the distillation column below the stages of contact with the acidic catalyst to provide an aqueous side- stream which is withdrawn from the distillation column, and an essentially water- free mixture of polyoxymethylene dimethyl ethers having values of n greater than 1 which mixture is withdrawn from the distillation column near its bottom. A source of methanol can be admixed with the feedstream, and/or into the stages of contact with the acidic catalyst.
Suitable acidic catalysts include at least one member of the group consisting of bentonites, montmorillonites, cation-exchange resins, and sulfonated fluoroalkylene resin derivatives, preferably comprises a sulfonated tetrafluoroethylene resin derivative. A preferred class of acidic catalysts comprises at least one cation-exchange resin of the group consisting- of styrene- divinylbenzene copolymers, acrylic acid-divinylbenzene copolymers, and methacrylic acid-divinylbenzene copolymers. Preferably, the heating of the bottom stream with the acidic
catalyst employs at least one distillation column with internal and/or external stages of contact with the acidic catalyst.
Another aspect this invention is an integrated process which further comprises formation of the feedstream by a process comprising continuously contacting methanol in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, methanol, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture to predominantly condense methanol, and adsorb formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture comprising dihydrogen and carbon monoxide.
Preferably the resulting liquid source of formaldehyde contains about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than 5 percent water, and is recovered by using at least one continuous adsorption column with cooling to temperatures in a range downward from about 100°C to 25°C.
For a more complete understanding of the present invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawing and described below by way of examples of the invention.
BRIEF DESCRIPTION OF THE DRAWING
FIGURE 1 to FIGURE 4 are schematic flow diagrams depicting a preferred aspects of the present invention for continuous catalytic production of polyoxymethylene dimethyl ethers by chemical conversion of methanol and formaldehyde in which a feedstream comprising a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is heated with the heterogeneous acidic catalyst in a catalytic distillation column with internal stages of contact. A liquid
portion of the effluent of condensation, containing polyoxymethylene dimethyl ethers, is contacted with an anion exchange resin disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture, and fractionated to provide suitable components for blending into diesel fuel.
The feedstream in the integrated process depicted in FIGURE 1 is a stream of formaldehyde in methanol derived from dehydrogenation of dimethyl ether.
The feedstream in the integrated process depicted in
FIGURE 2 is a stream of formaldehyde in methanol derived from dehydrogenation of methanol.
The feedstream in the integrated process depicted in FIGURE 3 is a stream of aqueous formaldehyde in methanol derived from oxidation of dimethyl ether. In this aspect of invention, recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether, preheated against reactor product, and then fed to the formaldehyde reactor.
The feedstream in the integrated process depicted in FIGURE 4 is a stream of aqueous formaldehyde in methanol derived from oxidative dehydrogenation of dimethyl ether. In this aspect of invention, recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether, preheated against reactor product, and then fed to the formaldehyde reactor.
GENERAL DESCRIPTION
The improved processes of the present invention employ a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst. Suitable component^ include any acidic compound soluble in the feedstream, preferably an organic compound soluble in a feedstream of about 30 to about 85
percent by weight formaldehyde in methanol solution containing less than 5 percent water.
A preferred class of condensation promoting components capable of activating a heterogeneous acidic catalyst includes members of the group consisting of low boiling, monobasic organic acids, more preferably acetic acid or formic acid.
In general, after the feedstream is heated with the heterogeneous catalyst it will contain a mixture of organic oxygenates at least one of which is of higher molecular weight than the starting formaldehyde and methanol. For example, effluent mixtures can comprise water, methanol, formaldehyde, methylal and other polyoxymethylene dimethyl ethers having a structure represented by the type formula
CH3θ(CΗ2θ)nCH3
in which formula n is a number ranging between 1 and about 15, preferably between 1 and about 10. More preferably the mixture contains a plurality of polyoxymethylene dimethyl ethers having values of n are in a range from 2 to about 7. Conditions of reaction include temperatures in a range from about 50° to about 300°C, preferably in a range from about 150° to about 250°C.
Stoichiometry of this condensation may be expressed by the following equations;
CH3OCH3 + n CH20 => CH30(CH20)nCH3
2 CH2OH + m CH 0 => CH30(CH2θ)mCH3 + H2O
which may be combined as in the following equation when n is equal to m;
CH3CCH3 + 2 CH3OH + 2n CH2θ = 2 CH3θ(CH2θ)rιCH3 + H2O
As shown above, the synthesis of methylal and higher polyoxymethylene dimethyl ethers from dimethyl ether, methanol, and formaldehyde is a reversible reaction that yields
water as a co-product. Under certain conditions at least a portion of the water may be consumed in a dehydrogenation reaction expressed by the following equations;
CH3OCH3 + CH3OH + H20 - - > 3 CH20 + 3 H2
and
CH3OCH3 + H20 <=> 2 CH3OH
Sources of dimethyl ether useful herein are predominantly dimethyl ether, preferably at least about 80 percent dimethyl ether by weight, and more preferably about 90 percent dimethyl ether by weight. Suitable dimethyl ether sources may contain other oxygen containing compounds such as alkanol and/or water, preferably not more than about 20 percent methanol and/or water by weight, and more preferably not more than about 15 percent methanol and/or water by weight.
According to the present invention, the ratio of formaldehyde to methanol in the feedstreams is any mole ratio which results in the production of the desired oxygenated organic compound. The ratio of formaldehyde to methanol is preferably between about 10: 1 and about 1 : 10 moles. The ratio of formaldehyde to methanol is preferably between about 5: 1 and about 1:5 moles. More preferably, the ratio of formaldehyde to methanol is between about 2: 1 and about 1:2 moles.
The feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is heated in a catalytic distillation column with an acidic catalyst, which is heterogeneous to the feedstream, under conditions of reaction sufficient to convert formaldehyde and methanol present to methylal and higher polyoxymethylene dimethyl ethers. Examples of the solid acidic catalyst for use in the present invention include cation exchange resins, sulfonated fluoroalkylene resin derivatives, and crystalline aluminosilicates.
Cation exchange resins that can be used in the present invention may be carboxylated or sulfonated derivatives, but sulfonated derivatives are preferred because of the high reaction yield that can be attained. Ion exchange resins that can be used may be gel-type cation exchange resins or macroporous (macroreticular) cation-exchange resins, but the latter as exemplified by Amberlite 200C of Organc Co, Ltd. and Lewalit SP112 of Bayer A.G. are preferred because of the high reaction yield that can be attained. Specific examples of useful ion exchange resins include a styrene-divinylbenzene copolymer, an acrylic acid-divinylbenzene copolymer, a methacrylic acid- divinylbenzene copolymer, etc.
A sulfonated tetrafluoroethylene resin derivative (trade name, Naflon H) is preferably used as a sulfonated fluoroalkylene resin derivative.
The most desirable of these solid acidic catalysts are macroreticular cation exchange resins having sulfonate groups.
According to the present invention, the ratio of formaldehyde to dimethyl ether in the feedstreams is any mole ratio which results in the production of the desired oxygenated organic compound. The ratio of formaldehyde to dimethyl ether is preferably between about 10: 1 and about 1:10 moles. The ratio of formaldehyde to dimethyl ether is preferably between about 5:1 and about 1 :5 moles. More preferably, the ratio of formaldehyde to dimethyl ether is between about 2: 1 and about 1:2 moles.
According to an integrated process of the invention a source of formaldehyde is formed by subjecting methanol in the vapor phase to dehydrogenation in the presence of a catalytically effective amount of a catalyst preferably containing copper and zinc as well as tellurium and/or selenium and/or sulfur, if appropriate in the form of the oxides. Oxide catalysts which can contain copper, zinc and tellurium, are particularly useful. One class of preferred catalysts comprises copper, zinc and selenium or tellurium as catalyst components in an atomic ratios of 1 :0.01-
0.5:0.005-0.5, preferably 1 :0.05-0.5:0.01-0.4, with the proviso that the amount of zinc is at least equal to the amount of selenium or tellurium present.
Preparations of suitable catalysts for dehydrogenation of methanol according to the invention are described in, for example, U.S. Patent Number 4,014,939, U.S. Patent Number
4,054,609, and U.S. Patent Number 4,354,045 which patents are specifically incorporated herein in their entirety by reference.
The catalyst used in the present invention may be prepared by any one of conventional procedures known to those skilled in the art, for example, precipitation method, thermal decomposition method, or deposition and drying method. Any of these procedures may be properly selected based on the raw material to be used.
Suitable raw materials for catalyst useful in the present invention include a copper salt of a mineral acid such as copper nitrate, copper chloride, copper sulfate, copper sulfite, copper hydroxide, copper oxide, basic copper carbonate, metallic copper, and the like as a source of copper; a zinc salt of a mineral acid such as zinc nitrate, zinc chloride, zinc sulfate, zinc sulfite, zinc hydroxide, zinc oxide, metallic zinc and the like as a source of zinc; and selenic acid, selenious acid, selenium oxide, or metallic selenium and the like as a source of selenium. Further, zinc selenide, zinc selenate, zinc selenite, and the like may be used as a source of both zinc and selenium, and copper selenide may be used as a source of both copper and selenium.
Such catalysts can be prepared, for example, by kneading copper oxide with zinc oxide and tellurium dioxide (and/or selenium dioxide and/or ammonium sulfate) in the presence of water, drying the mixture at 130° C. and then pressing it to form pills, with or without admixture of a carrier. Suitable raw materials may be formed to a particle having a desired shape which may be tablet, sphere or the like and the average diameter of the particles thus formed should be more than 1 mm, preferably 2 to 5 mm. Catalyst particles are then reduced in a
reductive atmosphere, for example, in two steps, first at a temperature of 100° to 300°C, preferably 150° to 250°C for more than 0.2 hour, preferably 0.5 to 1 hour and then at the temperature of 500° to 750°C, preferably 600° to 700°C for more than 0.1 hour, preferably 0.5 to 1 hour.
In the oxide catalyst of the type mentioned, the copper oxide is completely or partially reduced to metallic copper, during use, by the hydrogen formed on dehydrogenation of methanol.
In some cases it is advantageous to reduce the catalyst prior to use, for example with gaseous hydrogen at 200° to 600°C.
The process may be carried out with the catalysts in the form of a fixed bed in the reaction vessel, for example a tubular reactor. However, a fluidized bed can also be used.
In the present method, methanol may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order to better communicate the present invention, still another preferred aspect of the invention is depicted schematically in FIGURE 1. In integrated processes of this invention a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, formic acid, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde and formic acid therein; and separating the resulting liquid source of formaldehyde from a gaseous mixture comprising dihydrogen and carbon monoxide.
Referring now to FIGURE 1, a mixture containing dimethyl ether in substantially liquid form is unloaded, for example from a road tanker (not shown), into dimethyl ether storage vessel 12 which supplies charge pump 1 4 through conduit 1 3 . Charge pump 1 4 transfers the liquid dimethyl ether through conduit 16 into manifold 92 which is in flow communication with heat exchanger 1 04 and formaldehyde reactor 90 through conduit 94.
Formaldehyde reactor 90 contains particulate dehydrogenation catalyst disposed in a plurality of tubes of a vertical heat exchanger which is maintained at elevated temperatures by circulation of heating fluid to the shell side of formaldehyde reactor 90 through conduit 88 from furnace 80. Heating fluid is returned to furnace 80 through conduits 96 and 86 by means of pump 84. Natural gas or other suitable fuel is supplied to furnace fuel manifold 82 through conduit 74 from fuel supply 72 . As described below, at least a portion of the co- product hydrogen is used as fuel for combustion with air in furnace 80.
In this embodiment of the invention, CuZnTeO/Al2θ3 or CuZnSeO/AhOg catalyzes the conversion of dimethyl ether to formaldehyde by a reversible dehydrogenation reaction at temperatures in a range from about 500° to 750°, preferably in a range from about 600° to 700°C:
CH3OCH3 + H2O <- - > 2CH2O + 2H2
Gaseous effluent from formaldehyde reactor 90 is transferred through conduit 102 , cooled against the reactor feedstream in exchanger 104 and then passed through conduit 106 into an adsorption tower 100 where formaldehyde and dimethyl ether are separated from a mixture of gaseous co- products including hydrogen, methane, and oxides of carbon. Adsorption tower 100 contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with an adsorption liquid. Formaldehyde in methanol from the bottom of the adsorption tower is circulated in a pump-around to a lower section of the tower through conduits 1 12 and 1 1 6 , cooler 120 ,
and conduit 1 1 8 by means of pump 1 1 4 . Methanol is supplied to an upper section of the adsorption separation tower through conduit 122 by means of pump 48. Overhead temperatures are in a range of about 15° to about 55°C, preferably about 20° to about 40°C.
A gaseous overhead stream including hydrogen, methane, and oxides of carbon is transferred through conduit 1 24 and into furnace fuel manifold 82 by means of blower 126. As needed additional fuel such as natural gas is supplied to manifold 82 from a suitable fuel source 72 through conduit 74.
Formaldehyde solution from the adsorption tower is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water.
It should be apparent that effluent from the adsorption tower is a valuable product in itself. A portion of the stream can optionally be diverted from adsorption tower 100 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether. The stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
The adsorption liquid containing formaldehyde, formic acid and dimethyl ether in methanol is transferred from adsorption tower 100 through conduits 1 12 and 18 , by means of pump 1 14 , and into ether recovery column 30 , where unreacted dimethyl ether is separated from the effluent stream to form a resulting liquid mixture of formaldehyde, formic acid and methanol. A dimethyl ether fraction is taken overhead through conduit 32 and into condenser 34 where a liquid condensate is formed. A suitable portion of the liquid condensate is refluxed into column 30 through conduits 35 and 36 while another portion of the condensate is supplied to manifold" 92 through conduit, 37 and 39 by means of pump 38.
Conduit 28 supplies pump 40 with liquid from the bottom of ether recovery column 30. A suitable portion of the liquid stream from the bottom of column 30 is transferred through conduits 41 and 42 , by means of pump 40 , and into reboiler 43 which is in flow communication with the bottom of the column through conduit 44. A liquid stream from the bottom of column 30 is transferred through conduit 45 into reactive distillation column 50 , where simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus. Optionally, a stream containing methanol from storage vessel 46 maybe admixed with the feedstream, and/or into the stages of contact with the acidic catalyst of the reactive distillation column 50. Charge pump 48 can transfer methanol into the reactive distillation column 50 through conduits 47 and 49.
Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter- currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
The overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54. A suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56. A product stream containing methylal is transferred through conduit 57 to product storage (not shown). Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50. A suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom
of the column by means of conduit 66. A product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown). Preferably, an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 58.
In order to better communicate the present invention, still another preferred aspect of the invention is depicted schematically in FIGURE 2. In integrated processes of this invention a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting methanol in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, formic acid, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde and formic acid therein; and separating the resulting liquid source of formaldehyde from a gaseous mixture comprising dihydrogen and carbon monoxide.
In the feedstream preparation aspect of the invention which is described herein below, gaseous methanol is dehydrogenated in the presence of catalytically effective amount of a catalyst consisting of copper, zinc and tellurium or selenium as catalyst components. Referring now to FIGURE 2, a mixture containing methanol in substantially liquid form is unloaded, for example from a road tanker (not shown), into methanol storage vessel 46 which supplies charge pump 48 through conduit 47. Charge pump 48 transfers the liquid methanol through conduit
42 and conduit 92 which is in flow communication with heat exchanger 104 and formaldehyde reactor 90 through conduit 94.
Formaldehyde reactor 90 contains particulate dehydrogenation catalyst disposed in a plurality of tubes of a vertical heat exchanger which is maintained at temperatures from about 500° to 750°C by circulation of heating fluid to the shell side of formaldehyde reactor 90 through conduit 88 from furnace 80. Heating fluid is returned to furnace 80 through conduits 96 and 86 by means of pump 84. Natural gas or other suitable fuel is supplied to furnace fuel manifold 82 through conduit 81 from a suitable fuel source 83. As described below, at least a portion of the co-product hydrogen is used as fuel for combustion with air in furnace 80.
In this embodiment of the invention, CuZnTeO or CuZnSeO catalyzes the conversion of methanol to formaldehyde by a reversible dehydrogenation reaction at temperatures in a range from about 500° to 750°, preferably in a range from about 600° to 700°C:
CH3OH <- - > CH2O + H2
Gaseous effluent from formaldehyde reactor 90 is transferred through conduit 1 02 , cooled against the reactor feedstream in exchanger 104 and then passed through conduit 1 06 into a separation tower 1 00 where formaldehyde and methanol are separated from a mixture of gaseous co-products including hydrogen, methane, and oxides of carbon. Adsorption tower 1 00 contains a high efficiency packing or other means for contacting counter- currently the gaseous stream with an adsorption liquid. Adsorption liquid from the bottom of adsorption separation tower 1 00 is circulated in a pump-around on the adsorption tower through conduits 1 12 and 1 16 , cooler 120 , and conduit 1 1 8 by means of pump 1 14. Methanol is diverted from conduit 42 , through conduit 44 to supply pump 1 14. Overhead temperatures in separation tower 100 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C. A gaseous overhead stream including hydrogen, methane,
and oxides of carbon is transferred through conduit 1 22 and into furnace fuel manifold 82 by means of blower 1 24. As needed additional fuel such as natural gas is supplied to manifold 82 through conduit 81 from a suitable fuel source 83 .
Formaldehyde solution from the adsorption tower is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water. It should be apparent that effluent from the adsorption tower is a valuable product in itself. A portion of the stream can optionally be diverted from adsorption tower 1 00 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether. The stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
Adsorption liquid containing formaldehyde, formic acid and water in methanol is transferred from adsorption tower 1 00 through conduits 1 12 and 45 , by means of pump 1 1 4 , and into reactive distillation column 50. Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
The overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54. A suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56. A product stream containing methylal is transferred through conduit 57 to product storage (not shown). Conduit 59 supplies pump 60 with liquid containing higher molecular weight
polyoxymethylene dimethyl ethers from the bottom of column 50. A suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66. A product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown). Preferably, an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 58.
In order to better communicate the present invention, still another preferred aspect of the invention is depicted schematically in FIGURE 3. In this integrated process a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of an oxidation promoting catalyst comprising tungsten oxide as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous oxidation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
According to an integrated process of the invention a source of formaldehyde is formed by subjecting dimethyl ether in the vapor phase to hydration and oxidation in the_ presence a catalytically effective amount of an oxidation promoting catalyst comprising tungsten oxide as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising
formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous mixture to predominantly condense water and adsorb formaldehyde therein; and separating the resulting aqueous source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
According to this aspect of the present invention, the ratio of dioxygen to total dimethyl ether is, according to the present invention, any mole ratio which results in the production of the desired source of formaldehyde. The ratio of dioxygen to ether and, if present, alkanol is preferably between about 1 : 1 and about 1 : 1000 moles. More preferably, the ratio of dioxygen to dimethyl ether is between about 1 : 1 and about 1 : 100 moles. Most preferably, the ratio of dioxygen to dimethyl ether is between about 1 : 1 and about 1 : 10 moles.
Operating conditions of reaction usually fall in the following ranges: Dimethyl ether: 1 mol percent up to 17.4 mol percent
Air: 99 mol percent to 82.6 mol percent Reaction temperature: 200° to 450°C
Space velocity: 1 ,000-20,000 hr" l
Preferable conditions are as follows:
Dimethyl ether: 3 mol percent to 12 mol percent Reaction temperature: 250° to 400°C.
Space velocity: 1 ,000-10,000 hr- 1
The dioxygen can be added to the reaction mixture as pure molecular oxygen, or diluted with an inert gas such as nitrogen or argon. It is preferred to keep the dioxygen at no more than 10 mole percent of the entire reaction feed so as 4o avoid the formation of explosive mixtures.
According to the present invention, within the oxidation reaction zone dimethyl ether is oxidized with a source of dioxygen in the presence of an oxidation-promoting catalytic composition containing, as an essential ingredient, a metal oxide with or without up to about 10 percent of a supplemental inorganic compound based upon the total weight of metal oxide and supplemental inorganic compounds
Suitable metal oxide catalysts have been developed for reacting dimethyl ether with a source of dioxygen to produce formaldehyde, as described in U.S. Patent Number 3,655,771, or U.S. Patent Number 4,753,916.
Well known methods of preparing suitable tungsten oxide include adding to ammonium tungstate concentrated hydrochloric or nitric acid, to precipitate the oxide. Oxide is molded into tablets or supported on inert carriers, such as alumina, Carborundum, pumice or the like. Advantageously, vanadium oxide, boron oxide, molybdenum oxide, phosphoric acid, an ammonium salt thereof, ammonium chloride or the like is added to tungsten oxide in an amount of not more than 10%, in order to maintain the activity of tungsten oxide at the original level and to obtain a catalyst having a sufficient mechanical strength to withstand operating conditions during its useful catalytic life. The addition thereof results in the combination with tungsten oxide and consequently the aggregatability of powdered tungsten oxide is enhanced, molding of the oxide is facilitated and the oxide is hardened.
For example, 5 percent by weight of phosphoric acid is added to tungsten oxide powder, produced by any generally known method, and the resulting mixture is milled well with water into a paste. This paste is dried, ground into 12 mesh, size- controlled and shaped into tablets by a tablet-forming machine. These tablets are sufficiently dried, and thereafter calcined in air at 500°C for 7 to 8 hours to obtain very hard tablets.
The present invention further provides a method for selective oxidation of dimethyl ether to formaldehyde in the
presence of an catalytically effective amount of a composition of matter comprising β - Mo(i -x)Wx O3, where x is a number between 0 and 1, preferably where x is a number between 0 and 0.5, and more preferably where x is 0 or a number between 0 and 0.1. Using such catalytic material, the selective oxidation of dimethyl ether to formaldehyde is conducted at temperatures in a range from about 200° to about 450°C, and more preferably in a range from about 250° to about 400°C. Preferred operating pressures are from about 1 to about 100 kPa, and more preferably from about 6 to about 15 kPa.
One method for preparation of a composition comprising β - Mθ(i-χ)Wx O3, comprises spray-drying a solution of molybdic acid or molybdic and tungstic acids in appropriate concentrations and heating the resulting powder at a temperature of from about 275° to about 450° C. Another method comprises sputtering a molybdenum or mixed metal oxide target in appropriate concentrations onto a thermally floating substrate in an atmosphere comprising oxygen and an inert gas wherein the oxygen is in an amount from about 5 to about 50 volume percent. Most preferred compositions comprising β - Mθ(i-x)Wxθ3, are where x is 0 or a number between 0 and 0.05. This phase of the specified metal or mixed metal oxide has a distorted three dimensional RCO3 structure based on corner-linked octahedra. The thermal stability of the beta phase of M0O3, can be improved by tungsten substitution as evidenced by the beta to alpha transformation temperature of about 530°C of Moo.95Wxo.05Q3, compared to about 450°C of Moθ3.
Another method for preparation of a composition comprising the "beta" phase of the specified metal and mixed metal oxides (β - Mθ(i-x)Wx O3) can be prepared in films by sputtering or spin coating.
In the present method, dimethyl ether may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
Referring now to the upper portion of FIGURE 3, a mixture containing dimethyl ether in substantially liquid form is supplied from dimethyl ether storage vessel 12 to pump 1 4 through conduit 13 , and into feed manifold 92 through conduit 1 5. By means of blower 78 a recycle stream of wet gas is transferred into feed manifold 92 through conduit 98 . A gaseous stream containing dioxygen and dinitrogen from a source (not shown) is supplied to compressor 94 through conduit 93 . Compressed gas is transferred through conduit 95 , combined in feed manifold 92 with the recycle stream of wet gas from the formaldehyde adsorber and the dimethyl ether. The resulting feed mixture is heated against reactor effluent in heat exchanger 76 , and transferred into oxidation reactor 90 through conduit 91 .
The mole ratio of fresh air feed to dimethyl ether is about 3.5, and the mole ratio of recycled gas to fresh air feed is about 2.1. Oxidation reactor 90 is a vertical heat exchanger. The tubes are filled with catalyst pellets. (The upper and lower regions of the tubes contain pellets of inert material.) Typically, a portion of heat generated in the catalyst bed is diverted to steam generation within oxidation reactor 90 thereby providing cooling of effluent from the bed (not shown). A thermal fluid is vaporized on the shell side and circulated to a steam generator to generate steam at pressures of up to 300 psig.
Within the oxidation reaction zone of reactor 90 is an oxidation-promoting catalyst, preferably consisting essentially of a metal oxide component with or without a supplemental inorganic compound. In a preferred embodiment on this invention, tungsten oxide catalysts are used because they give almost complete oxidation to formaldehyde at much lower temperatures than are required for the silver-catalyzed dehydrogenation reaction.
Gaseous effluent from oxidation reactor 90 is transferred through conduit 96 , cooled against the reactor feedstream in exchanger 76 and then passed through conduit 97 into spray column 1 00 where a solution of aqueous formaldehyde in
methanol is formed. Formaldehyde solution from the bottom of spray column 1 00 , at temperatures in a range downward from about 100°C to about 75°C, is supplied to pump 1 04 through conduit 103 . Formaldehyde solution from the spray column is generally from about 30 to about 85 percent by weight formaldehyde in methanol solution containing less than about 5 percent water and less than 350 ppm of formic acid.
It should be apparent that effluent from the spray column is a valuable product in itself. A portion of the stream can optionally be diverted from adsorption tower 100 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether. The stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
The formaldehyde solution from pump 1 04 is combined with a solution of formaldehyde in methanol supplied from the bottom of adsorption column 1 10 through conduits 1 13 and 108 , by means of pump 1 14. The combination forms a stream which is circulated to the top of spray column 100 through conduit 106. It is important to maintain the temperature of the pump- around stream above about 70°C to prevent paraformaldehyde formation. Optionally, a portion of the cooling required in spray column 100 may be obtained by including a heat exchanger in the flow through conduit 1 06.
A gaseous overhead stream from spray column 100 is transferred through conduit 102 into adsorption column 1 1 0 , which contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with aqueous adsorption liquid. A solution of formaldehyde in methanol from the bottom of adsorption column 1 10 is circulated in a pump- around to a lower section of the column through conduits 1 13 and 1 1 5 , cooler 1 1 6 , and conduit 1 1 7 by means of rjump 1 14 .
As needed, methanol for the adsorption is supplied to a section of adsorption column 1 10 by means of pump 48 through conduit 125 , cooler 126 , and conduit 128 . Further up the
column, pump-arounds may be cooled to successively lower temperatures. In some configurations, the lower pump- around stream is not cooled at all.
A vapor side draw from adsorption column 1 1 0 is transferred through conduit 1 12 and mixed with fresh air as previously described. The adsorber overhead passes through conduit 1 1 8 into condenser 122 . An appropriate amount of condensate is formed and refluxed to the top section of the adsorber column through conduit 124. Overhead temperatures in adsorption column 1 1 0 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C. Gases are vented from condenser 122 through conduit 120 to disposal, typically, in a thermal oxidation unit (not shown).
The absorber overhead, which contains trace amounts of formaldehyde (about 10-30 ppm), is treated in several ways by catalytic or thermal converter to oxidize hydrocarbons and recuperative heat exchange. Typically, 170 psig to 200 psig steam is generated to improve overall economics of preferred embodiments of the invention.
A portion of the solution of formaldehyde in methanol is diverted from pump 1 04 into reactive distillation column 50 through conduit 45. In reactive distillation column 50 simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus. Optionally, a stream containing methanol from storage vessel 46 may by fed into the reactive distillation column 50. Charge pump 48 transfers methanol in substantially liquid form into the reactive distillation column 50 through conduits 47 and 49.
Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight
polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
The overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54. A suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduits 55 and 56. A product stream containing methylal is transferred through conduit 58 to product storage (not shown). Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50. A suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66. A product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown). Preferably, an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 72. The side stream from column 50 is transferred by means of pump 74 through conduit 75 to waste disposal (not shown).
In this embodiment of the invention, tungsten oxide catalyzes the conversion of dimethyl ether to formaldehyde by an oxidation reaction at temperatures in a range from about 350° to about 600°C , preferably in a range from about 400° to about
500°C:
CH3OCH3 + O2 - - > 2CH 0 + H θ"
In this case, a large excess of air is necessary to obtain maximum yields and to avoid explosive feed concentrations.
Some flexibility exists in the explosive limits, depending upon the temperature, pressure, and normal moisture content of the air. However, normal practical limitations appear to set a lower boundary between 8 mol percent and 10 mol percent in the reactor feed.
Several side reactions occur, especially those producing carbon monoxide, formic acid, and dimethyl ether. However, because of a lower reaction temperature, the extent of these reactions is smaller than in the silver-catalyzed process.
In order to better communicate the present invention, still another preferred aspect of the invention is depicted schematically in FIGURE 4. In this integrated process a feedstream comprising methanol, formaldehyde and a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst is provided by contacting dimethyl ether in the vapor phase with a catalytically effective amount of an oxidative dehydrogenation promoting catalyst comprising silver as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, methanol, dioxygen, diluent gas, carbon dioxide and water vapor; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor. In this aspect of invention, recycle gas from the formaldehyde absorber is combined with air, mixed with dimethyl ether, preheated against reactor product, and then fed to the formaldehyde reactor.
According to the present invention, within the oxidation reaction zone dimethyl ether is oxidized with a source of dioxygen in the presence of an oxy-dehydrogenation catalytic composition containing, as an essential ingredient, .silver with or without up to about 10 percent of a supplemental inorganic compound based upon the total weight of metal oxide and supplemental inorganic compounds. Suitable oxy-
dehydrogenation catalysts have been developed for converting methanol with a source of dioxygen to produce formaldehyde, as described in U.S. Patent Number 5,401 ,884, U.S. Patent
Number 5,102,838, U.S. Patent Number 4,786,743, U.S. Patent Number 4,521 ,618, U.S. Patent Number 4,474,996 and U.S. Patent Number 4,359,587.
The starting materials are fed through a silver-containing fixed-bed catalyst installed in a vertical tubular reactor. The catalyst preferably comprises silver crystals having a particle size of from 0.1 to 3 mm, in particular from 0.2 to 2.5 mm. The fixed- bed catalyst can have a multi-layer structure through arrangement of the silver crystals in layers of different particle size.
The starting mixture of dimethyl ehter vapor, oxygen- containing gas, and, if used, steam and inert gas is preferably passed through the tubular reactor from top to bottom.
Otherwise, the process is carried out in one step by passing the starting mixture through the fixed catalyst bed at from 550° to 750°C, in particular from 600° to 720°C, particularly advantageously at from 660° to 700°C. The process is preferably carried out continuously at from 0.5 to 3 bar, in particular at from 0.8 to 2 bar, preferably at from 1 to 1.5 bar. The residence times in the catalyst zone are from 0.001 to 1 second, preferably from 0.002 to 0.1 second. The reaction gases leaving the catalyst zone are advantageously cooled within a short time, for example to below 350°C. The cooled gas mixture can expediently be fed to an adsorption tower, in which the formaldehyde is washed out of the gas mixture by means of water.
In the present method, dimethyl ether may be used alone, or methanol and dimethyl ether can be used in admixture with each other to produce formaldehyde.
Referring now to the upper portion of FIGURE 4, a mixture containing dimethyl ether in substantially liquid form is supplied from dimethyl ether storage vessel 12 to pump 1 4 through
conduit 13. Dimethyl ether is transferred through conduit 1 6 into feed manifold 92 . A recycle stream of wet gas is transferred into feed manifold 92 by means of blower 88. A gaseous stream containing dioxygen and dinitrogen from a source (not shown) is supplied to compressor 94 through conduit 93 . Compressed gas is transferred through conduit 95 , combined in feed manifold 92 with the recycle stream of wet gas from the formaldehyde adsorber and the dimethyl ether. The resulting mixture is heated against reactor effluent in heat exchanger 80 , and transferred into oxidation reactor 90 through conduit 82 and feed manifold 84
Formaldehyde reactor 90 contains an oxidative dehydrogenation catalyst disposed in a thin layer directly above a vertical heat exchanger where effluent from the catalyst layer is promptly cooled. Boiler feed water at about 110° to 130°C is supplied through conduit 85 to the heat exchanger for generation of low pressure steam in the lower section of the formaldehyde reactor. The steam is transferred through conduit 86 , mixed with the preheated mixture of dimethyl ether, wet recycle gas and air stream in feed manifold 84 , and transferred into formaldehyde reactor 90. Steam is metered into the preheated methanol-air mixture to control the reactor outlet temperature. The mole ratio of fresh air feed to methanol is between 0.5 and 2.0, preferably about 1.25 and typically the mole ratio of dimethyl ether to steam is about 3. The pressure is only slightly above atmospheric. Since the catalyst layers are less than one inch in thickness, the pressure drop is negligible.
In this embodiment of the invention, metallic silver catalyzes the conversion of dimethyl ether to formaldehyde by a reversible dehydrogenation reaction at temperatures from about 500° to 700°C:
CH3OCH3 + l/2 02 - - > 2CH20 + H2
The oxidative dehydrogenation catalyst is generally silver crystals supported on a stainless steel mesh, or a shallow bed of silver crystals, spherical particles, or granules. The reaction is
endothermic, and theoretical equilibrium is approximately 50 percent yield at 400°C, 90 percent at 500°C, and 99 percent at 700°C. To conveniently sustain elevated reaction temperatures required to obtain high yields, a portion of the hydrogen formed is oxidized to water. Formation of water is exothermic and provides heat to maintain the endothermic hydrogenation reaction. Heat is also provided by the direct oxidation of methanol:
CH3OH + 1/2 O2 - - > CH2O + H2O
These reactions are rapid and therefore the process is essentially adiabatic. At 650°C, the reaction is substantially complete with contact times of less than 0.01 second. Methanol conversion in the reactor is typically between 65 percent and 80 percent, depending largely on the amount of steam introduced at the methanol vaporization step. Formaldehyde is lost by several side reactions, including those producing co-products including carbon monoxide, carbon dioxide, methane, formic acid, and methyl formate.
To minimize side reactions, it is important to avoid excess oxygen and to operate with exposure time of products and reactants to the catalyst at high temperatures as short as possible. An excess of methanol or methanol and steam is also important, serving to avoid an explosive feed composition. A mixture containing between 6.7 mol percent and 36.5 mol percent methanol in air at 1 atm constitutes a severe explosion hazard.
Gaseous effluent from oxidation reactor 90 is transferred through conduit 96 , cooled against the reactor feedstream in exchanger 80 and then passed to an absorption system, where aqueous formaldehyde is absorbed in methanol. The effluent gases flow through conduit 98 into spray column 100 where a solution of formaldehyde is formed. Formaldehyde solution from the bottom of spray column 1 00 , at temperatures in a range downward from about 100°C to about 75°C, is supplied to pump 104 through conduit 103. A portion of the aqueous
formaldehyde is transferred through conduit 45 into reactive distillation column 50. Formaldehyde solution from the spray column is generally about 55 percent by weight formaldehyde, about 43 methanol weight percent about 2 weight percent water and less than 350 ppm of formic acid.
It should be apparent that effluent from the spray column is a valuable product in itself. A portion of the stream can optionally be diverted from adsorption tower 1 00 for delivery to a destination (not shown) where the stream may subsequently be separated to recover, for example, formaldehyde and methanol and/or dimethyl ether. The stream can alternatively be utilized as a source of feed stock for chemical manufacturing.
Formaldehyde solution is combined with a solution of formaldehyde supplied from the bottom of adsorption column 1 10 through conduits 1 13 and 108 , by means of pump 1 14 , and circulated to the top of spray column 100 through conduit 1 06 . It is important to maintain the temperature of the pump-around stream above about 70°C to prevent paraformaldehyde formation. Optionally, a portion of the cooling required in spray column 1 00 may be obtained by including a heat exchanger in the flow through conduit 1 06 .
A gaseous overhead stream from spray column 1 00 is transferred through conduit 1 02 into adsorption column 1 10 , which contains a high efficiency packing or other means for contacting counter-currently the gaseous stream with aqueous adsorption liquid. A dilute aqueous formaldehyde from the bottom of adsorption column 1 10 is circulated in a pump-around to the bottom section of the column through conduits 1 13 and 1 15 , cooler 1 16 , and conduit 1 17 by means of pump 1 14.
Further up the column pump-arounds are be cooled to successively lower temperatures. In this embodiment of the invention a liquid side stream is supplied to pump 124 through conduit 125 , transferred through manifold 127 , cooled in cooler 126 , and returned to adsorption column 1 10 through conduit 128 .
In some configurations, the lower pump-around stream is not cooled at all. Caustic solution may be added to the chilled water to improve absorber performance, but it leaves traces of sodium as a contaminant in the product.
A vapor side draw from adsorption column 1 1 0 is transferred through conduit 1 1 2 and mixed with fresh air as previously described.
The adsorber overhead passes through conduit 1 1 8 into condenser 122 . An appropriate amount of condensate is formed and refluxed to the top section of the adsorber column through conduit 123 . Overhead temperatures in adsorption column 1 10 are in a range of about 15° to about 55°C, preferably about 30° to about 40°C. Gases are vented from condenser 122 through conduit 120 to disposal, typically, in a thermal oxidation unit (not shown).
The absorber overhead, which contains trace amounts of formaldehyde (about 10-30 ppm), is treated in several ways by catalytic or thermal converter to oxidize hydrocarbons and recuperative heat exchange. Typically, 170 psig to 200 psig steam is generated to improve overall economics of preferred embodiments of the invention.
A portion of the solution of formaldehyde in methanol is diverted from pump 104 into reactive distillation column 50 through conduit 45. In reactive distillation column 50 simultaneous chemical reaction and multicomponent distillation are carried out coextensively in the same high efficiency, continuous separation apparatus. Optionally, a stream containing methanol from storage vessel 46 may by fed into the reactive distillation column 50. Charge pump 48 transfers methanol in substantially liquid form into the reactive distillation column 50 through conduits 47 and 49.
Solid acidic catalyst is present in the reactive distillation column 50 to allow solutions containing water, methanol, formaldehyde, methylal and one or more other
polyoxymethylene dimethyl ethers to be brought into solid-liquid contact counter-currently with the catalyst to form products including methylal and higher molecular weight polyoxymethylene dimethyl ethers. More volatile reaction products are taken overhead from the high efficiency separation apparatus, whereas water and less volatile reaction products are carried down the high efficiency separation apparatus.
The overhead vapor stream from reactive distillation column 50 is transferred through conduit 52 into condenser 54. A suitable portion of condensate from condenser 54 is refluxed into reactive distillation column 50 through conduit 56. A product stream containing methylal is transferred through conduit 58 to product storage (not shown). Conduit 59 supplies pump 60 with liquid containing higher molecular weight polyoxymethylene dimethyl ethers from the bottom of column 50. A suitable portion of liquid from the bottom of column 50 is transferred, by means of pump 60 , through conduits 62 and 63 into reboiler 64 which is in flow communication with the bottom of the column by means of conduit 66. A product stream containing higher molecular weight polyoxymethylene dimethyl ethers is transferred through conduit 68 to product storage (not shown). Preferably, an anion exchange resin is disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
An aqueous side stream containing low levels of unreacted formaldehyde and/or methanol is discharged from column 50 through conduit 72.
In view of the features and advantages of the continuous catalytic processes for direct condensation of formaldehyde and dimethyl ether to form a mixture containing one or more polyoxymethylene dimethyl ethers in accordance with this invention, as compared to the known methanol condensation systems previously used, the following example is given.
EXAMPLES 1 and 2
In these Examples a catalyst of copper, zinc and selenium was used at several elevated temperatures to convert a liquid feedstream of aqueous methanol and a gaseous feedstream of dimethyl ether, nitrogen and dihydrogen. Effluent of the fixed bed reactor was a gaseous dehydrogenation mixture including formaldehyde, dimethyl ether, dihydrogen and carbon monoxide.
A tubular quartz reactor was charged with 9.27 grams (5 cc) of the CuZnSe particles which had been sieved to 18-40 mesh. The tubular quartz reactor (approx. 10 mm inside diameter) was equipped with a quartz thermowell terminating at about the midpoint of the catalyst bed.
A liquid feed solution was prepared using 13.06 grams of water and 17.33 grams of methanol. The resulting solution was fed by a syringe pump into a preheat zone above the catalyst bed. Using mass flow controllers, a gaseous feedstream of 26.9 percent by volume dimethyl ether, 6.62 volume percent nitrogen and a balance of dihydrogen was also fed to the top of the reactor.
Liquid products from the reactor were collected in a cool
(0°C) 25 mL flask for subsequent weighing and GC analysis. Gases exiting the collection flask were analyzed by on-line GC using both TCD and FID detectors. Samples of liquid products were collected during sampling intervals of 40 and 80 minutes over an approximately 6 hour period of operation. Gas analyses were obtained by GC during each sampling interval.
Samples were collected while temperature of the catalyst bed was controlled to temperatures of about 600°C. Each sample was about 2.5 or 7 grams. Operating conditions and results are summarized in Tables I and II.
EXAMPLE 3
Products of several condensation runs were composited, and the composite vacuum filtered through a medium glass frit.
A 90 gram aliquot of filtrate was shaken with 20 grams of basic ion-exchange resin beads (DOWEX 66) which were then allowed to settle for one hour. The resulting supernatant liquid was then gravity filtered through a medium paper filter. A suitable amount (54 grams) of molecular sieve type 3 A, which had been activated by calcination at about 538°C, was mixed into the filtrate, and the mixture allowed to stand overnight at ambient temperatures. Liquid was separated from the sieve by vacuum filtration through a medium glass frit. A 45.97 gram aliquot of this acid- free, dry filtrate was charged to a small distillation apparatus consisting of a 100 mL 3-neck flask, a fractionating column and condenser. The charge was distilled into eight overhead fractions which were collected at temperature cuts according to the following schedule.
Schedule of Overhead and Bottom Temperatures
Fraction Temperatures. °C
Numl ?er Overhead Bottom
1 42 to 46 70 to 94
2 47 to 76 95 to 109
3 77 to 94 110 to 118
4 95 to 100 119 to 127
5 101 to 107 128 to 136
6 108 to 112 137 to 146
7 113 to 123 147 to 162
8 124 to 150 163 to 174
White solids (possibly paraformaldehyde) were observed in the column and condenser during cuts 2 through 4, but not thereafter. Composition of the distilled fraction and bottoms are given in Table III.
EXAMPLE 4
In this Example a silver catalyst in the form of needles was used at several elevated temperatures to provide a source of formaldehyde by oxidative dehydrogenation of dimethyl ether, steam and methanol. A tubular quartz reactor was charged with 3.83 grams (1 cc) of the silver needles. The tubular quartz reactor (approx. 10 mm inside diameter) was equipped with a quartz thermowell terminating at about the midpoint of the catalyst bed. Quartz wool was placed above the catalyst zone to assist in vaporizing liquid feed. The liquid feed solution containing 18.6 percent methanol and 81.4 percent by weight water was fed by a syringe pump into the preheat zone above the catalyst bed. Using mass flow controllers, a gaseous feedstream of 59.93 percent by volume dimethyl ether, 31.59 volume percent nitrogen and 8.48 percent by volume dioxygen was also fed to the top of the reactor. Samples were collected while temperature of the catalyst bed was controlled to temperatures in a range from about 400° to about 650°C. Operating conditions and results are summarized in Table IV.
EXAMPLE 5
In this Example a silver catalyst in the form of needles was used at several elevated temperatures to provide a source of formaldehyde by nonoxidative dehydrogenation of dimethyl ether and steam. The liquid feed of water was fed by a syringe pump into the preheat zone above the catalyst bed. Using mass flow controllers, a gaseous feedstream of 89.1 percent by volume dimethyl ether and 10.9 volume percent nitrogen was also fed to the top of the reactor. Samples were collected while temperature of the catalyst bed was controlled to temperatures in a range from about 400° to about 650°C. Operating conditions and results are summarized in Table V.
For the purposes of the present invention, "predominantly" is defined as more than about fifty percent. "Substantially" is defined as occurring with sufficient frequency or being present in
such proportions as to measurably affect macroscopic properties of an associated compound or system. Where the frequency or proportion for such impact is not clear, substantially is to be regarded as about twenty per cent or more. The term "essentially" is defined as absolutely except that small variations which have no more than a negligible effect on macroscopic qualities and final outcome are permitted, typically up to about one percent.
Table I
Dehydrogenation of Dimethyl Ether
Using a Catalyst of Copper, Zinc and Selenium
Temperature, ° C 599 596
Run Time, min 40 80
Gas Feed, mol percent
Nitrogen 6.62 6.62
DME 26.90 26.90
Dihydrogen 66.48 66.48
Liquid Feed, weight percent
Methanol 57.03 57.03
Water 42.97 42.97
Feed Rates
Gas scc/min 135 135
Liquid mL/min 0.07563 0.07563
Conversions, mole percent
Methanol 55.62 58.29
DME 17.33 14.87
Net MeO 27.75 26.69
Selectivities, percent
CO 3.66 3.27
002 13.94 15.08
Formaldehyde 66.29 67.15
Methylal 0 0
HPE 0..311 0..312
DME/MeOH 6.07 6.75
Carbon Balance 92.57 93.39
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety, and DME is dimethyl ether.
Table II
Dehydrogenation of Dimethyl Ether
Using a Catalyst of Copper, Zinc and Selenium
Temperature, ° C 599 596
Run Time, min 210 275
Gas Feed, mol percent
Nitrogen 6.62 6.62
DME 26.90 26.90
Dihydrogen 66.48 66.48
Liquid Feed, weight percent
Methanol 57.03 57.03
Water 42.97 42.97
Feed Rates
Gas scc/min 135 135
Liquid mL/min 0.07563 0.07563 Conversions, mole percent
Methanol 51.17 51.70
DME 13.64 16.33
Net MeO 23.63 25.95
Selectivities, percent
CO 2.78 2.80
002 15.15 17.31
Formaldehyde 70.63 68.01
Methylal 0 0
HPE 0..318 0..306
DME/MeOH 5.96 5.83
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety, and DME is dimethyl ether.
TABLE III
COMPOSITION OF OVERHEAD FRACTIONS AND BOTTOMS
Compound CH3θ(CH2θ)nCH3 where the value of n is:
Fraction Methylal Methanol Hemiacetals Trioxane 2 3 4 5 6 7
Starting 49.95 0.0 0.69 2.42 22.60 12.42 6.40 3.15 1 .45 0.61
1 97.21 0.95 0.05 0.0 0.46 0 0 0 0 0
2 93.83 2.52 0.38 0.0 2.84 0 0 0 0 0
3 20.81 12.92 8.85 2.39 54.80 0. 17 0 0 0 0
4 3.24 1 1 . 12 6.40 4.49 74.19 0.57 0 0 0 0
5 0.56 8.47 2.29 5.83 82.07 0.78 0 0 0 0
6 0.40 3.10 0. 16 7.21 88.05 1.08 0 0 0 0
7 0.43 0.99 0.0 9.38 86.60 2.55 0.05 0 0 0
8 0.32 0.47 0.0 1 1.77 82.98 4.37 0.08 0 0 0
Bottoms 0.2*9 0.02 0.0 0.54 1 .10 49.49 26. 19 13.05 6.34 2.96
Table IV Oxidative Dehydrogenation of Dimethyl Ether Using a Catalyst of Silver Needles
Temperature, ° C 397 508
Run Time, min 60 100
Gas Feed, mol percent
Nitrogen 31.59 31.69
DME 59.93 59.93
Dioxygen 8.48 8.48
Liquid Feed, weight percent
Methanol 18.6 18.6
Water 81.4 81.4
Feed Rates
Gas scc/min 146 146
Liquid mL/min 0.4125 0.4125
Conversions, mole percent
Methanol 9.21 10.55
DME 15.44 16.41
Net MeO 14.01 15.08
Dioxygen 94.40 93.85
Selectivities, percent
Light Alkanes 1.37 4.07
CO 18.19 20.15
CQ2 9.06 7.92
Formaldehyde 56.57 59.16
Methylal 0 0
HPE 0 0
DME/Methanol 3.23 3.20
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety, and DME is dimethyl ether.
Table IV Continued
Oxidative Dehydrogenation of Dimethyl Ether
Using a Catalyst of Silver Needles
Temperature, ° C 614 660
Run Time, min 150 195
Gas Feed, mol percent
Nitrogen 31.59 31.69
DME 59.93 59.93
Dioxygen 8.48 8.48
Liquid Feed, weight percent
Methanol 18.6 18.6
Water 81.4 81.4
Feed Rates
Gas scc/min 146 146
Liquid mL/min 0.4125 0.4125
Conversions, mole percent
Methanol 13.53 15.30
DME 17.18 23.94
Net MeO 16.34 21.96
Dioxygen 94.28 94.53
Selectivities, percent
Light Alkanes 19.47 28.59
CO 25.41 20.15
C02 5.29 3.39
Formaldehyde 45.79 37.70
Methylal 0 0
HPE 0 0
DME/Methanol 3.30 3.10
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety, and DME is dimethyl ether.
Table V
Nonoxidative Dehydrogenation of Dimethyl Ether
Using a Catalyst of Silver Needles
Temperature, ° C 408 51 1
Run Time, min 1 15 175
Gas Feed, mol percent
Nitrogen 10.9 10.9
DME 89.1 89.1
Liquid Feed, weight percent
Water 100 100
Feed Rates
Gas scc/min 102 102
Liquid mL/min 0.07563 0.07563
Conversions, mole percent
DME 3.63 2.56
Net MeO 3.63 2.56
Selectivities, percent
Light Alkanes 46.21 46.48
CO 0 0
002 0 0
Formaldehyde 53.79 53.52
Methylal 0 0
HPE 0 0
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety, and DME is dimethyl ether.
Table V Continued
Nonoxidative Dehydrogenation of Dimethyl Ether
Using a Catalyst of Silver Needles
Temperature, ° C 612 650
Run Time, min 290 465
Gas Feed, mol percent
Nitrogen 10.9 10.9
DME 89.1 89.1
Liquid Feed, weight percent
Water 100 100
Feed Rates
Gas scc/min 102 102
Liquid mL/min 0.07563 0.07563
Conversions, mole percent
DME 9.38 23.39
Net MeO 9.36 23.28
Selectivities, percent
Light Alkanes 53.06 52.51
CO 5.51 14.96
Cθ2 0.34 0.25
Formaldehyde 41.10 32.29
Methylal 0 0
HPE 0 0
Where HPE is higher polyoxymethylene dimethyl ethers which are CH3θ(CH2θ)nCH3 having n greater than 1, MeO is methoxy moiety and DME is dimethyl ether.
Claims
1. A process for catalytic production of a mixture of oxygenated organic compounds suitable as a blending component of fuel for use in compression ignition internal combustion engines, which process comprises providing a feedstream comprising methanol, a soluble condensation promoting component capable of activating a heterogeneous acidic catalyst, and a source of formaldehyde; and heating the feedstream with the heterogeneous acidic catalyst under conditions of reaction sufficient to form an effluent of condensation comprising water, methanol and one or more polyoxymethylene dimethyl ethers having a structure represented by the type formula
CH3θ(CH2θ)nCH3
in which formula n is a number from 1 to about 10.
2. The process according to claim 1 wherein the soluble condensation promoting component capable of activating the heterogeneous acidic catalyst comprises at least one member of the group consisting of low boiling, monobasic organic acids.
3. The process according to claim 1 wherein at least a liquid of the effluent containing polyoxymethylene dimethyl ethers is contacted with an anion exchange resin to form an essentially acid-free mixture.
4. The process according to claim 2 wherein the acidic catalyst comprises at least one member of the group consisting of bentonite, montmorillonite, cation exchange resins, and sulfonated fluoroalkylene resin derivatives.
5. The process according to claim 2 wherein the acidic catalyst comprises at least one cation exchange resin of the group consisting of styrene-divinylbenzene copolymers, -acrylic acid- divinylbenzene copolymers, and methacrylic acid-divinylbenzene copolymers.
6. The process according to claim 2 wherein the acidic catalyst comprises a sulfonated tetrafluoroethylene resin derivative.
7. The process according to claim 1 wherein the heating of the feedstream with the acidic catalyst is carried out at temperatures in a range from about 45° to about 90°C and employs at least one catalytic distillation column having internal and/or external stages of contact with the acidic catalyst and internal zones to separate methylal from higher polyoxymethylene dimethyl ethers.
8. The process according to claim 7 wherein at least a liquid portion of the effluent containing polyoxymethylene dimethyl ethers is contacted with an anion exchange resin disposed within a section of the distillation column below the stages of contact with the acidic catalyst to form an essentially acid-free mixture.
9. The process according to claim 8 wherein the essentially acid-free mixture of polyoxymethylene dimethyl ethers is fractionated within a section of the distillation column below the stages of contact with the acidic catalyst to provide an aqueous side-stream which is withdrawn from the distillation column, and an essentially water-free mixture of polyoxymethylene dimethyl ethers having values of n greater than 1 which mixture is withdrawn from the distillation column near its bottom.
10. The process according to claim 7 wherein a source of methanol is admixed with the feedstream, and/or into the stages of contact with the acidic catalyst.
11. The process according to claim 1 which further comprises formation of the feedstream by a process comprising continuously contacting methanol in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid comprising methanol and adsorbing formaldehyde therein; and separating a gaseous mixture, comprising predominantly dihydrogen and carbon monoxide, from resulting liquid comprising dimethyl ether, methanol, formaldehyde and formic acid.
12. The process according to claim 1 which further comprises formation of the feedstream by a process comprising continuously contacting dimethyl ether in the vapor phase with a catalytically effective amount of a catalyst consisting of copper, zinc and a member selected from the group consisting of sulfur, selenium and tellurium as catalyst components at elevated temperatures to form a gaseous dehydrogenation mixture comprising formaldehyde, dimethyl ether, dihydrogen and carbon monoxide; cooling the gaseous dehydrogenation mixture with an adsorption liquid comprising methanol and adsorbing formaldehyde therein; and separating a gaseous mixture, comprising predominantly dihydrogen and carbon monoxide, from resulting liquid comprising dimethyl ether, methanol, formaldehyde and formic acid.
13. The process according to claim 1 1 or claim 12 wherein the catalyst comprises copper, zinc and selenium or tellurium as catalyst components in atomic ratios of 1 :0.05- 0.5:0.01-0.5 with the proviso that the amount of zinc is at least equal to the amount of selenium or tellurium present in the catalyst, and wherein the elevated temperatures are in a range from about 500° to about 750°C.
14. The process according to claim 1 which further comprises formation of the feedstream by a process comprising continuously contacting a gaseous feedstream. comprising dimethyl ether, dioxygen and diluent with a catalytically effective amount of an oxidation promoting catalyst comprising tungsten oxide as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous oxidation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
15. The process according to claim 1 which further comprises formation of the feedstream by a process comprising continuously contacting a gaseous feedstream comprising dimethyl ether, dioxygen and diluent with a catalytically effective amount of an oxidative dehydrogenation promoting catalyst comprising silver as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, dimethyl ether, dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor; cooling the gaseous oxidation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
16. A process for oxidative dehydrogenation of dimethyl ether to form a source of formaldehyde by a process comprising continuously contacting a gaseous feedstream comprising dimethyl ether, dioxygen and diluent gas with a catalytically effective amount of an oxidative dehydrogenation promoting catalyst comprising silver as an essential catalyst component at elevated temperatures to form a gaseous mixture comprising formaldehyde, methanol, dioxygen, diluent gas, carbon dioxide and water vapor; cooling the gaseous dehydrogenation mixture with an adsorption liquid and adsorbing formaldehyde therein; and separating the resulting liquid source of formaldehyde from a mixture of gases comprising dioxygen, diluent, carbon monoxide, carbon dioxide and water vapor.
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US09/190,315 | 1998-11-12 | ||
US09/190,699 US6265528B1 (en) | 1998-11-12 | 1998-11-12 | Preparation of polyoxymethylene dimethyl ethers by acid-activated catalytic conversion of methanol with formaldehyde formed by oxy-dehydrogenation of dimethyl ether |
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Family Cites Families (2)
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AT305231B (en) * | 1971-03-04 | 1973-02-12 | Oesterr Hiag Werke Ag | Continuous process for the production of methylal |
DD245868A1 (en) * | 1985-04-30 | 1987-05-20 | Leuna Werke Veb | PROCESS FOR PREPARING FORMALS |
-
1999
- 1999-09-09 AU AU60324/99A patent/AU6032499A/en not_active Abandoned
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