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WO1996033015A1 - Pretreatment of catalyst support to enhance catalytic dehydrogenation of a hydroquinone - Google Patents

Pretreatment of catalyst support to enhance catalytic dehydrogenation of a hydroquinone Download PDF

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Publication number
WO1996033015A1
WO1996033015A1 PCT/US1996/002532 US9602532W WO9633015A1 WO 1996033015 A1 WO1996033015 A1 WO 1996033015A1 US 9602532 W US9602532 W US 9602532W WO 9633015 A1 WO9633015 A1 WO 9633015A1
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WO
WIPO (PCT)
Prior art keywords
catalyst
catalyst support
earth metal
rare earth
support
Prior art date
Application number
PCT/US1996/002532
Other languages
French (fr)
Inventor
Scott W. Cowley
Mark A. Plummer
Original Assignee
Marathon Oil Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Marathon Oil Company filed Critical Marathon Oil Company
Priority to AU51733/96A priority Critical patent/AU5173396A/en
Publication of WO1996033015A1 publication Critical patent/WO1996033015A1/en
Priority to MXPA/A/1997/006862A priority patent/MXPA97006862A/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C46/00—Preparation of quinones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0205—Impregnation in several steps
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
    • C01B17/0495—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by dissociation of hydrogen sulfide into the elements
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the present invention relates to a process for preparing a catalyst system used to dehydrogenate a hydroquinone, and more particularly, to such a process wherein the support of the catalyst system is pretreated to enhance the conversion of the hydroquinone to its corresponding quinone and hydrogen.
  • Catalytic dehydrogenation of a hydroquinone to its corresponding quinone and hydrogen is generally known.
  • the following publications incorporated herein by reference; Plummer, "Sulfur and Hydrogen from H 2 S", Hydrocarbon Processing, April 1987; U.S. Patent 4,592,905 to Plummer ⁇ t at, and U.S. Patent 5,334,363 to Plummer. all teach processes for recovering solid sulfur and hydrogen gas from a gas stream containing hydrogen suifide, wherein the step of catalytically dehydrogenating an anthrahydroquinone to its corresponding anthraquinone and hydrogen is integral to each process.
  • hydrogen suifide contained in a gas stream such as a hydrocarbon refinery off-gas
  • a solvent also having an anthraquinone dissolved therein.
  • the hydrogen suifide and anthraquinone are reacted in solution to obtain solid sulfur and the corresponding anthrahydroquinone of the anthraquinone.
  • the solid sulfur product is recovered from the reaction solution and the anthraquinone is regenerated for recycle to the hydrogen suifide reaction step by catalytically dehydrogenating the anthrahydroquinone.
  • Hydrogen gas also results as a product of the anthraquinone regeneration step.
  • the process taught by Plummer in Hydrocarbon Processing investigates a number of different supported metal catalyst systems for use in the regeneration step to determine the effect of the different systems on the conversion of anthrahydroquinone to its corresponding anthraquinone. It is believed that the selectivity of the conversion step is strongly dependent on the catalyst system parameters, which, if improperly selected, can undesirably result in reduced yields of the corresponding anthraquinone and concurrently increased yields of less desirable compounds, such as the corresponding anthrone and anthranol.
  • the Plummer process found that the specific type of metal catalyst selected is an important parameter for the catalytic conversion of the anthrahydroquinone to anthraquinone.
  • the Plummer process also found that the catalytic dehydrogenation step is strongly dependent on the characteristics of the material selected as a support for the metal catalyst.
  • selective dehydrogenation of the anthrahydroquinone back to anthraquinone is favored by the use of only slightly acidic catalyst supports such as silica or alumina, or by the use of basic supports such as magnesium oxide. More acidic catalyst supports such as silica-alumina undesirably yield relatively low conversions of anthrahydroquinone to anthraquinone and yield relatively high conversions of anthrahydroquinone to anthrone.
  • the present invention recognizes a need for an improved catalytic dehydrogenation process that converts a hydroquinone to hydrogen gas and its corresponding quinone. Accordingly, it is an object of the present invention to provide a catalytic dehydrogenation process having enhanced selectivity for the conversion of a hydroquinone to its corresponding quinone. More particularly, it is an object of the present invention to provide a catalyst system including a catalyst support, having enhanced selectivity for the catalytic conversion of a hydroquinone to its corresponding quinone. It is further an object of the present invention to provide a process for pretr ⁇ ating a catalyst support that enhances the selectivity thereof when employed in a process for catalytically converting a hydroquinone to its corresponding quinone.
  • the present invention is a process for preparing a catalyst system containing a catalyst support and an associated catalyst used to catalytically dehydrogenate a hydroquinone, selectively converting the hydroquinone to its corresponding quinone and hydrogen gas.
  • the present invention is a process for pretreating the catalyst support used in conjunction with the associated catalyst to dehydrogenate the hydroquinone.
  • the present invention is the catalyst system prepared in accordance with the process disclosed herein.
  • the present invention is a process employing a quinone to recover sulfur and gaseous hydrogen from a hydrogen sulfide-containing gas stream, wherein the catalyst system of the present invention is used to regenerate the quinone from its corresponding hydroquinone.
  • the present process of pretreating a catalyst support comprises selecting a porous catalyst support from among sized alumina or silica and calcining the selected support.
  • the calcined support is contacted with an aqueous solution containing a salt selected from the group consisting of alkali metal salts, alkaline earth metal salts, rare earth metal salts, and mixtures thereof, thereby treating the surface of the support with the selected salt.
  • the salt-treated support is then dried and calcined converting the salt to a corresponding metal oxide.
  • the desired pretreated catalyst support is produced thereby, having a sufficient quantity of metal oxide placed on the catalyst support to reduce the acidity of the support.
  • the present process of preparing a catalyst system comprises selecting a metal catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof.
  • a pretreated catalyst support prepared in the above-described manner is contacted with an aqueous solution containing the selected metal catalyst, preferably in a metal salt form.
  • the metal catalyst solution augments the metal oxide on the pretreated catalyst support with the selected metal catalyst.
  • the metal catalyst-treated catalyst support is then dried and caldned producing the desired catalyst system thereby, comprising the catalyst placed on the pretreated catalyst support.
  • the catalyst system of the present invention has enhanced utility in the selective conversion of a hydroquinone to its corresponding quinone and hydrogen gas. The invention will be further understood, both as to its use and composition, from the accompanying description.
  • the figure is a plot of temperature programmed desorption (TPD) profiles for a catalyst support treated in accordance with the process of the present invention and for a comparable untreated catalyst support.
  • TPD temperature programmed desorption
  • the present invention relates to the catalytic dehydrogenation of a hydroquinone to its corresponding quinone and hydrogen (H 2 ).
  • Hydroquinones having utility herein include anthrahydroquinones, benzohydroquinones, naphthahydroquinones, and mixtures thereof.
  • Corresponding quinones having utility herein include anthraquinones, benzoquinones, naphthaquinones, and mixtures thereof, respectively.
  • the dehydrogenation reaction is typically one stage of a multi-stage industrial process, wherein the quinone is regenerated from the hydroquinone for use in another stage of the process and hydrogen is recovered as a product gas.
  • the dehydrogenation reaction is employed to regenerate a quinone from a hydroquinone as a stage of an industrial process to recover sulfur from hydrogen suifide (H 2 S).
  • a selected quinone is dissolved in a selected polar organic solvent.
  • Suitable polar organic solvents include N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N- dimethylformamaide, sulfolane (tetrahydrothiophene- 1 ,1 -dioxide), acetonitrile, 2-nitropropane, propylene carbonate and mixtures thereof.
  • the most preferred solvent is N-methyl-2-pyrrolidinone (NMP).
  • Suitable quinones are those having relatively high solubilities in the above-listed polar organic solvents, and include such anthraquinones as ethyl anthraquinone, t-butyl anthraquinone, t- amyl anthraquinone, s-amyl anthraquinone or mixtures thereof.
  • the quinone-containing solvent is fed to an H 2 S conversion reactor along with a feed gas stream containing a hydrogen suifide gas. If the feed gas stream additionally contains large quantities of other gases that are inert to the process, such as nitrogen, carbon dioxide, methane or other low molecular weight hydrocarbon gases, the feed gas stream is initially contacted with the quinone-containing solvent in an absorber ahead of the H j S conversion reactor.
  • gases such as nitrogen, carbon dioxide, methane or other low molecular weight hydrocarbon gases
  • the solvent preferentially solubilizes the hydrogen suifide in the feed gas stream upon contact forming a reaction solution that is maintained in the reactor at a temperature from about 0°C to about 70 °C, an H 2 S partial pressure from about 0.05 to about 4.0 atmospheres, and for a time sufficient to convert the hydrogen suifide and quinone in the reaction solution to insoluble sulfur and the corresponding hydroquinone.
  • the reaction solution Upon conversion of the reactants, the reaction solution is removed from the H 2 S conversion reactor and the insoluble sulfur product, in the form of -- , or other sulfur polymers, is separated from the reaction solution by filtration, centrifugation or any other means known in the art.
  • the remainder of the reaction solution which contains the polar organic solvent, hydroquinone, any unreacted quinone, and any un reacted constituents of the feed gas stream, is heated to a temperature from about 100°C to about 150°C at atmospheric pressure and fed to a flash tank. Any unreacted feed gas constituents, such as hydrogen suifide and carbon dioxide, are recovered from the reaction solution in the flash tank and recycled to the H 2 S conversion reactor.
  • the remaining solution is withdrawn from the flash tank and preferably heated further to a temperature from about 150°C to about 350 °C at a pressure at least sufficient to prevent solvent boiling.
  • the heated solution is then fed to a dehydrogenation reactor where the hydroquinone is catalytically converted to quinone and hydrogen gas under the above-stated temperature and pressure conditions.
  • a catalyst system including a metal catalyst and a catalyst support, wherein the catalyst system is prepared in a specific manner, unexpectedly results in improved hydrogen and quinone selectivity when a hydroquinone is catalytically dehydrogenated.
  • pretreatment of the catalyst support in a specific manner to reduce the acidity thereof unexpectedly results in improved hydrogen and quinone selectivity.
  • the present invention results in decreased production of undesirable by-products, such as anthrones and/or anthranols, during the dehydrogenation reaction.
  • Pretreatment of the catalyst support comprises selecting a porous catalyst support from among either alumina (Al j 0 3 ) or silica (SiO ).
  • the catalyst support has a surface area of at least about 100 m*/g and preferably at least about 200 m 2 /g.
  • the catalyst support can be crushed and sieved to a desired average particle size greater than about 0.3 mm, and preferably greater than about 0.5 mm.
  • the sized catalyst support is calcined for several hours or more at a temperature of at least about 120°C, and preferably at least about 500°C.
  • the calcined support is then contacted with an aqueous solution of a salt selected from the group consisting of alkali metal salts, alkaline earth metal salts, rare earth metal salts, and mixtures thereof.
  • a salt selected from the group consisting of alkali metal salts, alkaline earth metal salts, rare earth metal salts, and mixtures thereof.
  • a preferred salt is a rare earth metal salt, such as a salt of lanthanum, and in particular lanthanum nitrate.
  • Contacting of the catalyst support with the salt solution can be accomplished by metering a solution of the selected salt onto the support while mixing and shaking the support to obtain good contacting between the support surface and the selected salt.
  • Contacting of the catalyst support with the salt solution can alternatively be accomplished by other means apparent to the skilled artisan. In any case, contacting between the catalyst support and the selected salt places the selected salt on the surface of the catalyst support.
  • Treatment of the catalyst support is completed by removing the salt- treated support from the aqueous salt solution and drying the support with an air flow heated to a temperature of at least about 120°C.
  • the dried catalyst support is then caJ ⁇ ned, preferably under substantially the same conditions as described above, thereby converting the selected salt on the surface of the catalyst support to a corresponding basic alkali metal oxide, alkaline earth metal oxide, rare earth metal oxide, or mixture thereof, respectively.
  • a preferred basic metal oxide is a rare earth metal oxide, such as an oxide of lanthanum.
  • a sufficient quantity of the basic metal oxide is placed on the support to reduce the acidity thereof.
  • the amount of metal oxide placed on the catalyst support is generally within a range between about 1.0 weight % and about 10.0 weight %, and preferably within a range between about 2.0 weight % and about 5.0 weight %.
  • Preparation of the catalyst system is implemented with selection of a metal catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof.
  • the platinum group metals as defined herein consist of platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os) and indium (Ir). Of the metal catalysts disclosed herein the platinum group metals are preferred, and platinum is most preferred.
  • the selected metal catalyst is placed on the pretreated catalyst support by contacting the pretreated catalyst support with a solution of the selected metal catalyst, preferably in the form of one of its salts, such as a solution of platinum chloride.
  • Contacting of the catalyst support with the selected metal catalyst solution can be accomplished in substantially the same manner as described above or, alternatively, by other means apparent to the skilled artisan. In any case, contacting between the catalyst support and the selected metal catalyst solution places the metal catalyst on the surface of the catalyst support augmenting the metal oxide treatment. A sufficient quantity of the metal catalyst is placed on the support to enable effective performance of the resulting catalyst system in the conversion of hydroquinone to its corresponding quinone.
  • the amount of metal catalyst placed on the pretreated catalyst support is generally within a range between about 0.01 weight % and about 3.0 weight %, and preferably within a range between about 0.1 weight % and about 2.0 weight %.
  • the resulting catalyst system is then dried and calcined in substantially the same manner as described above.
  • the catalyst system prepared in the manner of the present invention has specific utility in the above-described dehydrogenation reaction of the sulfur recovery process, wherein the catalyst converts a hydroquinone dissolved in the polar solvent to hydrogen gas that is recovered as a commercial product and to the corresponding quinone that is recycled to the H 2 S conversion reactor.
  • a series of test runs are performed in a dehydrogenation reactor to determine the selectivity that different catalyst systems exhibit in the conversion of an anthrahydroquinone to its corresponding anthraquinone and hydrogen.
  • the reactor feed composition for all runs is prepared comprising a mixture of t-butyl anthrahydroquinone (H BAQ) and t-butyl anthraquinone (TBAQ) in a N-methyl-2-pyrrolidinone (NMP) solvent.
  • H BAQ t-butyl anthrahydroquinone
  • TBAQ t-butyl anthraquinone
  • NMP N-methyl-2-pyrrolidinone
  • the relative quantity of total quinone species (H-TBAQ and TBAQ) in the feed is 25 % by weight.
  • the mole ratio of HJBAQ to TBAQ in the feed is 76.0:24.0.
  • the catalytic dehydrogenation reactor is charged with a different catalyst system comprising a catalyst and a catalyst support.
  • the reactor is a packed stainless steel tube having a diameter of 1.27 cm.
  • the different catalyst systems are characterized below:
  • the silica (Si0 2 ) type catalyst support is Davidson 57 having a pore volume of 1.0 cm 3 and contains 99.5 % Si0 2 by weight.
  • the alumina (AljO, ) type catalyst support is Norton having a pore volume of 0.57 to 0.67 cm 3 and contains 99.85 % A ⁇ O, by weight.
  • Each of the catalyst supports has a surface area of 260 m 2 /g.
  • Catalyst system A is a catalyst system of the present invention having a pretreated catalyst support prepared in accordance with the manner described herein.
  • the support is initially crushed and sieved to an average particle size of 0.56 mm.
  • the sized support is calcined overnight at a temperature of 500 °C.
  • Lanthanum oxide (LajOa) is placed on the calcined support by dropwise adding an aqueous solution of lanthanum nitrate to the support while continuously mixing and shaking the support, thereby producing a lanthanum nitrate on the support surface.
  • the treated support is then dried with air flow for 2 hours at 120*C and calcined overnight at 500 °C to obtain the desired lanthanum oxide-treated support.
  • a platinum (Pt) catalyst is then placed on the pretreated support by dropwise adding an aqueous solution of platinum chloride (PtCI to the pretreated support while continuously mixing and shaking the support.
  • the catalyst system is dried with air flow for 2 hours at 120°C, calcined overnight at 500°C, cooled to room temperature, and stored in a desiccator for use.
  • Catalyst systems B and C are prior art catalyst systems prepared in substantially the same manner as described above, but without pretreatment of the catalyst support.
  • the alumina catalyst support is crushed and sieved to a particle size from 14 to 20 mesh.
  • the amount of catalyst system charged to the packed bed of the reactor in each run is 7.8 cm,.
  • the reactor is maintained at a temperature between 265°C and 275°C and at a hydrogen pressure between 430 kPa and 500 kPa.
  • the feed is retained in the dehydrogenation reactor for a residence time of 1 minute.
  • the product is then removed from the reactor and analyzed to determine the degree of total HjTBAQ conversion and conversion of H 2 TBAQ to TBAQ and hydrogen. The results are set forth in the table below.
  • Run 1 demonstrates the enhanced performance of a catalyst system of the present invention for selectively converting H 2 TBAQ to TBAQ and hydrogen.
  • the catalyst system of run 1 has a pretreated catalyst support as compared to the prior art catalyst systems of runs 2 and 3 having untreated catalyst supports.
  • Sample 1 is an alumina catalyst support treated in accordance with the process of the present invention, placing lanthanum oxide on the catalyst support.
  • Sample 2 is an alumina catalyst support substantially identical to the catalyst support of Sample 1 , but lacking a lanthanum oxide treatment.
  • Each sample is initially contacted with ammonia to saturate the surface thereof.
  • the ammonia saturated samples are then heated to drive off the adsorbed ammonia, while measuring the amount of ammonia desorbed as a function of temperature by a technique termed temperature programmed 96/33015 1 1 PC17US96/02532
  • TPD deso ⁇ tion
  • the desorbed ammonia from each sample is collected in sulfuric add solutions and the solutions are titrated upon completion of the TPD runs to determine the total amount of desorbed ammonia from each sample.
  • the results of the TPD runs are shown in the Figure, wherein a TPD profile for each sample is generated by plotting the intensity of the ammonia signal on the y-axis (which is proportional to the rate of ammonia desorption) against temperature on the x-axis.
  • the amount of ammonia desorbed from the sample is a function of the amount of ammonia adsorbed onto the sample, which in turn is a function of the acidity of the sample. Accordingly, a sample having more ammonia desorbed therefrom is relatively more acidic than a sample having less ammonia desorbed therefrom.
  • the TPD profile of Sample 2 in the Figure shows that untreated alumina contains both weak and strong acid sites.
  • the weak acid sites are evidenced on the TPD profile of Sample 2 by a temperature peak around 290°C, corresponding to a maximum desorption rate at this temperature.
  • the strong acid sites are evidenced on the TPD profile of Sample 2 by a pronounced shoulder centered around 400 °C.
  • the area under the TPD profile of Sample 2 is greater than that of Sample 1 indicating that the treated alumina desorbs less ammonia than the untreated alumina and is, therefore, less acidic than the untreated alumina
  • the TPD profile of Sample 1 exhibits a temperature peak around 290°C corresponding to the temperature peak of Sample 2, indicating the presence of weak acid sites on Sample 1 , there are fewer such sites on Sample 1 as evidenced by a lower peak.
  • the TPD profile of Sample 1 also does not exhibit the shoulder centered around 400 ⁇ C exhibited by the TPD profile of Sample 2, suggesting that treatment of the alumina catalyst support in the manner of the present invention substantially reduces the number of strong acid sites thereon.
  • the first sample is a palladium catalyst on a ⁇ -alumina support that has been prepared in accordance with the process of the present invention, pretreating the catalyst support by placing lanthanum oxide thereon.
  • the second sample is a palladium catalyst on a ⁇ -alumina support substantially identical to the treated catalyst support of the first sample, but lacking lanthanum oxide.
  • the catalyst concentration of both samples is 0.5 % by weight.
  • the lanthanum oxide concentration of the first sample is 7.0 % by weight.
  • a methanol dehydration reaction is carried out in the presence of each catalyst system sample at 300°C and the relative rates of dimethyl ether (DME) production for each sample are measured.
  • DME dimethyl ether
  • a higher rate of DME production indicates the presence of more acid sites on the catalyst system because such sites are required for the dehydration reaction.
  • DME production in the presence of the first sample is 1.5 mole %, while DME production in the presence of the second sample is 10.9 mole %.

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Abstract

A process is provided for preparing a catalyst system containing a catalyst support and an associated catalyst used to catalytically dehydrogenate a hydroquinone. In accordance with the process, the catalyst support is pretreated by selecting a porous alumina of silica catalyst support and contacting it with an aqueous solution of an alkali metal salt, alkaline earth metal salt, or rare earth metal salt to produce the corresponding metal oxide on the surface of the support in a quantity sufficient to reduce the acidity thereof. The metal oxide-treated support is then contacted with a metal catalyst to produce a catalyst system having enhanced utility in the selective conversion of a hydroquinone to its corresponding quinone and hydrogen gas.

Description

PRETREATMENTOFACATALYSTSUPPORTTOENHANCE CATALYTICDEHYDROGENATIONOFAHYDROQUINONE
This is a continuation-in-part application of application Serial No. 08/315,174 filed on September 29, 1994, which is a continuation-in-part application of application Serial No. 08/172,007 filed on December 22, 1993.
BACKGROUND OF THE INVENTION Technical Field: The present invention relates to a process for preparing a catalyst system used to dehydrogenate a hydroquinone, and more particularly, to such a process wherein the support of the catalyst system is pretreated to enhance the conversion of the hydroquinone to its corresponding quinone and hydrogen.
Background Information:
Catalytic dehydrogenation of a hydroquinone to its corresponding quinone and hydrogen is generally known. For example, the following publications incorporated herein by reference; Plummer, "Sulfur and Hydrogen from H2S", Hydrocarbon Processing, April 1987; U.S. Patent 4,592,905 to Plummer βt at, and U.S. Patent 5,334,363 to Plummer. all teach processes for recovering solid sulfur and hydrogen gas from a gas stream containing hydrogen suifide, wherein the step of catalytically dehydrogenating an anthrahydroquinone to its corresponding anthraquinone and hydrogen is integral to each process. In accordance with the above-referenced prior art processes, hydrogen suifide contained in a gas stream, such as a hydrocarbon refinery off-gas, is dissolved in a solvent also having an anthraquinone dissolved therein. The hydrogen suifide and anthraquinone are reacted in solution to obtain solid sulfur and the corresponding anthrahydroquinone of the anthraquinone. The solid sulfur product is recovered from the reaction solution and the anthraquinone is regenerated for recycle to the hydrogen suifide reaction step by catalytically dehydrogenating the anthrahydroquinone. Hydrogen gas also results as a product of the anthraquinone regeneration step. The process taught by Plummer in Hydrocarbon Processing investigates a number of different supported metal catalyst systems for use in the regeneration step to determine the effect of the different systems on the conversion of anthrahydroquinone to its corresponding anthraquinone. It is believed that the selectivity of the conversion step is strongly dependent on the catalyst system parameters, which, if improperly selected, can undesirably result in reduced yields of the corresponding anthraquinone and concurrently increased yields of less desirable compounds, such as the corresponding anthrone and anthranol. The Plummer process found that the specific type of metal catalyst selected is an important parameter for the catalytic conversion of the anthrahydroquinone to anthraquinone. The Plummer process also found that the catalytic dehydrogenation step is strongly dependent on the characteristics of the material selected as a support for the metal catalyst. In particular, the Plummer process found that selective dehydrogenation of the anthrahydroquinone back to anthraquinone is favored by the use of only slightly acidic catalyst supports such as silica or alumina, or by the use of basic supports such as magnesium oxide. More acidic catalyst supports such as silica-alumina undesirably yield relatively low conversions of anthrahydroquinone to anthraquinone and yield relatively high conversions of anthrahydroquinone to anthrone.
The present invention recognizes a need for an improved catalytic dehydrogenation process that converts a hydroquinone to hydrogen gas and its corresponding quinone. Accordingly, it is an object of the present invention to provide a catalytic dehydrogenation process having enhanced selectivity for the conversion of a hydroquinone to its corresponding quinone. More particularly, it is an object of the present invention to provide a catalyst system including a catalyst support, having enhanced selectivity for the catalytic conversion of a hydroquinone to its corresponding quinone. It is further an object of the present invention to provide a process for pretrβating a catalyst support that enhances the selectivity thereof when employed in a process for catalytically converting a hydroquinone to its corresponding quinone. It is yet another object of the present invention to provide a process for recovering sulfur and gaseous hydrogen from a hydrogen sulfide-containing gas stream employing a quinone, wherein a dehydrogenation catalyst effectively regenerates the quinone from its corresponding hydroquinone. These objects and others are achieved in accordance with the invention described hereafter.
SUMMARY OF THE INVENTION
In accordance with one embodiment, the present invention is a process for preparing a catalyst system containing a catalyst support and an associated catalyst used to catalytically dehydrogenate a hydroquinone, selectively converting the hydroquinone to its corresponding quinone and hydrogen gas. In accordance with another embodiment, the present invention is a process for pretreating the catalyst support used in conjunction with the associated catalyst to dehydrogenate the hydroquinone. In accordance with a further embodiment, the present invention is the catalyst system prepared in accordance with the process disclosed herein. In accordance with a more particular embodiment, the present invention is a process employing a quinone to recover sulfur and gaseous hydrogen from a hydrogen sulfide-containing gas stream, wherein the catalyst system of the present invention is used to regenerate the quinone from its corresponding hydroquinone.
The present process of pretreating a catalyst support comprises selecting a porous catalyst support from among sized alumina or silica and calcining the selected support. The calcined support is contacted with an aqueous solution containing a salt selected from the group consisting of alkali metal salts, alkaline earth metal salts, rare earth metal salts, and mixtures thereof, thereby treating the surface of the support with the selected salt. The salt-treated support is then dried and calcined converting the salt to a corresponding metal oxide. The desired pretreated catalyst support is produced thereby, having a sufficient quantity of metal oxide placed on the catalyst support to reduce the acidity of the support.
The present process of preparing a catalyst system comprises selecting a metal catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof. A pretreated catalyst support prepared in the above-described manner is contacted with an aqueous solution containing the selected metal catalyst, preferably in a metal salt form. The metal catalyst solution augments the metal oxide on the pretreated catalyst support with the selected metal catalyst. The metal catalyst-treated catalyst support is then dried and caldned producing the desired catalyst system thereby, comprising the catalyst placed on the pretreated catalyst support. The catalyst system of the present invention has enhanced utility in the selective conversion of a hydroquinone to its corresponding quinone and hydrogen gas. The invention will be further understood, both as to its use and composition, from the accompanying description.
BRIEF DESCRIPTION OF THE DRAWINfi
The figure is a plot of temperature programmed desorption (TPD) profiles for a catalyst support treated in accordance with the process of the present invention and for a comparable untreated catalyst support.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention relates to the catalytic dehydrogenation of a hydroquinone to its corresponding quinone and hydrogen (H2). Hydroquinones having utility herein include anthrahydroquinones, benzohydroquinones, naphthahydroquinones, and mixtures thereof. Corresponding quinones having utility herein include anthraquinones, benzoquinones, naphthaquinones, and mixtures thereof, respectively. The dehydrogenation reaction is typically one stage of a multi-stage industrial process, wherein the quinone is regenerated from the hydroquinone for use in another stage of the process and hydrogen is recovered as a product gas.
For example, the dehydrogenation reaction is employed to regenerate a quinone from a hydroquinone as a stage of an industrial process to recover sulfur from hydrogen suifide (H2S). In the sulfur recovery process, a selected quinone is dissolved in a selected polar organic solvent. Suitable polar organic solvents include N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N- dimethylformamaide, sulfolane (tetrahydrothiophene- 1 ,1 -dioxide), acetonitrile, 2-nitropropane, propylene carbonate and mixtures thereof. The most preferred solvent is N-methyl-2-pyrrolidinone (NMP). Suitable quinones are those having relatively high solubilities in the above-listed polar organic solvents, and include such anthraquinones as ethyl anthraquinone, t-butyl anthraquinone, t- amyl anthraquinone, s-amyl anthraquinone or mixtures thereof.
The quinone-containing solvent is fed to an H2S conversion reactor along with a feed gas stream containing a hydrogen suifide gas. If the feed gas stream additionally contains large quantities of other gases that are inert to the process, such as nitrogen, carbon dioxide, methane or other low molecular weight hydrocarbon gases, the feed gas stream is initially contacted with the quinone-containing solvent in an absorber ahead of the HjS conversion reactor. In any case, the solvent preferentially solubilizes the hydrogen suifide in the feed gas stream upon contact forming a reaction solution that is maintained in the reactor at a temperature from about 0°C to about 70 °C, an H2S partial pressure from about 0.05 to about 4.0 atmospheres, and for a time sufficient to convert the hydrogen suifide and quinone in the reaction solution to insoluble sulfur and the corresponding hydroquinone.
Upon conversion of the reactants, the reaction solution is removed from the H2S conversion reactor and the insoluble sulfur product, in the form of -- , or other sulfur polymers, is separated from the reaction solution by filtration, centrifugation or any other means known in the art. The remainder of the reaction solution, which contains the polar organic solvent, hydroquinone, any unreacted quinone, and any un reacted constituents of the feed gas stream, is heated to a temperature from about 100°C to about 150°C at atmospheric pressure and fed to a flash tank. Any unreacted feed gas constituents, such as hydrogen suifide and carbon dioxide, are recovered from the reaction solution in the flash tank and recycled to the H2S conversion reactor. The remaining solution is withdrawn from the flash tank and preferably heated further to a temperature from about 150°C to about 350 °C at a pressure at least sufficient to prevent solvent boiling. The heated solution is then fed to a dehydrogenation reactor where the hydroquinone is catalytically converted to quinone and hydrogen gas under the above-stated temperature and pressure conditions.
In accordance with the present invention, it has been discovered that a catalyst system including a metal catalyst and a catalyst support, wherein the catalyst system is prepared in a specific manner, unexpectedly results in improved hydrogen and quinone selectivity when a hydroquinone is catalytically dehydrogenated. In particular, it has been discovered that pretreatment of the catalyst support in a specific manner to reduce the acidity thereof unexpectedly results in improved hydrogen and quinone selectivity. Correspondingly, the present invention results in decreased production of undesirable by-products, such as anthrones and/or anthranols, during the dehydrogenation reaction.
Pretreatment of the catalyst support comprises selecting a porous catalyst support from among either alumina (Alj03) or silica (SiO ). The catalyst support has a surface area of at least about 100 m*/g and preferably at least about 200 m2/g. The catalyst support can be crushed and sieved to a desired average particle size greater than about 0.3 mm, and preferably greater than about 0.5 mm. The sized catalyst support is calcined for several hours or more at a temperature of at least about 120°C, and preferably at least about 500°C. The calcined support is then contacted with an aqueous solution of a salt selected from the group consisting of alkali metal salts, alkaline earth metal salts, rare earth metal salts, and mixtures thereof. A preferred salt is a rare earth metal salt, such as a salt of lanthanum, and in particular lanthanum nitrate.
Contacting of the catalyst support with the salt solution can be accomplished by metering a solution of the selected salt onto the support while mixing and shaking the support to obtain good contacting between the support surface and the selected salt. Contacting of the catalyst support with the salt solution can alternatively be accomplished by other means apparent to the skilled artisan. In any case, contacting between the catalyst support and the selected salt places the selected salt on the surface of the catalyst support. Treatment of the catalyst support is completed by removing the salt- treated support from the aqueous salt solution and drying the support with an air flow heated to a temperature of at least about 120°C. The dried catalyst support is then caJάned, preferably under substantially the same conditions as described above, thereby converting the selected salt on the surface of the catalyst support to a corresponding basic alkali metal oxide, alkaline earth metal oxide, rare earth metal oxide, or mixture thereof, respectively. A preferred basic metal oxide is a rare earth metal oxide, such as an oxide of lanthanum.
A sufficient quantity of the basic metal oxide is placed on the support to reduce the acidity thereof. The amount of metal oxide placed on the catalyst support is generally within a range between about 1.0 weight % and about 10.0 weight %, and preferably within a range between about 2.0 weight % and about 5.0 weight %.
Preparation of the catalyst system is implemented with selection of a metal catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof. The platinum group metals as defined herein consist of platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os) and indium (Ir). Of the metal catalysts disclosed herein the platinum group metals are preferred, and platinum is most preferred. The selected metal catalyst is placed on the pretreated catalyst support by contacting the pretreated catalyst support with a solution of the selected metal catalyst, preferably in the form of one of its salts, such as a solution of platinum chloride.
Contacting of the catalyst support with the selected metal catalyst solution can be accomplished in substantially the same manner as described above or, alternatively, by other means apparent to the skilled artisan. In any case, contacting between the catalyst support and the selected metal catalyst solution places the metal catalyst on the surface of the catalyst support augmenting the metal oxide treatment. A sufficient quantity of the metal catalyst is placed on the support to enable effective performance of the resulting catalyst system in the conversion of hydroquinone to its corresponding quinone. The amount of metal catalyst placed on the pretreated catalyst support is generally within a range between about 0.01 weight % and about 3.0 weight %, and preferably within a range between about 0.1 weight % and about 2.0 weight %. The resulting catalyst system is then dried and calcined in substantially the same manner as described above.
The catalyst system prepared in the manner of the present invention has specific utility in the above-described dehydrogenation reaction of the sulfur recovery process, wherein the catalyst converts a hydroquinone dissolved in the polar solvent to hydrogen gas that is recovered as a commercial product and to the corresponding quinone that is recycled to the H2S conversion reactor.
The following examples demonstrate the practice and utility of the present invention, but are not to be construed as limiting the scope thereof.
EXAMPLE 1
A series of test runs are performed in a dehydrogenation reactor to determine the selectivity that different catalyst systems exhibit in the conversion of an anthrahydroquinone to its corresponding anthraquinone and hydrogen.
The reactor feed composition for all runs is prepared comprising a mixture of t-butyl anthrahydroquinone (H BAQ) and t-butyl anthraquinone (TBAQ) in a N-methyl-2-pyrrolidinone (NMP) solvent. The relative quantity of total quinone species (H-TBAQ and TBAQ) in the feed is 25 % by weight. The mole ratio of HJBAQ to TBAQ in the feed is 76.0:24.0.
In each test run, the catalytic dehydrogenation reactor is charged with a different catalyst system comprising a catalyst and a catalyst support. The reactor is a packed stainless steel tube having a diameter of 1.27 cm. The different catalyst systems are characterized below:
Catalyst Catalyst Wt % on Support Oxide W-%Q*fe
System Type Supped Type Iypβ nπftmpn-t
A Pt 2.75 Si02 LaA 2.50 B Pt 2.75 Si02
C Cr203 12 AIA
The silica (Si02) type catalyst support is Davidson 57 having a pore volume of 1.0 cm3 and contains 99.5 % Si02 by weight. The alumina (AljO, ) type catalyst support is Norton having a pore volume of 0.57 to 0.67 cm3 and contains 99.85 % A^O, by weight. Each of the catalyst supports has a surface area of 260 m2/g.
Catalyst system A is a catalyst system of the present invention having a pretreated catalyst support prepared in accordance with the manner described herein. The support is initially crushed and sieved to an average particle size of 0.56 mm. The sized support is calcined overnight at a temperature of 500 °C. Lanthanum oxide (LajOa) is placed on the calcined support by dropwise adding an aqueous solution of lanthanum nitrate
Figure imgf000011_0001
to the support while continuously mixing and shaking the support, thereby producing a lanthanum nitrate on the support surface. The treated support is then dried with air flow for 2 hours at 120*C and calcined overnight at 500 °C to obtain the desired lanthanum oxide-treated support. A platinum (Pt) catalyst is then placed on the pretreated support by dropwise adding an aqueous solution of platinum chloride (PtCI to the pretreated support while continuously mixing and shaking the support. The catalyst system is dried with air flow for 2 hours at 120°C, calcined overnight at 500°C, cooled to room temperature, and stored in a desiccator for use.
Catalyst systems B and C are prior art catalyst systems prepared in substantially the same manner as described above, but without pretreatment of the catalyst support. The alumina catalyst support is crushed and sieved to a particle size from 14 to 20 mesh.
The amount of catalyst system charged to the packed bed of the reactor in each run is 7.8 cm,. The reactor is maintained at a temperature between 265°C and 275°C and at a hydrogen pressure between 430 kPa and 500 kPa. In each run, the feed is retained in the dehydrogenation reactor for a residence time of 1 minute. The product is then removed from the reactor and analyzed to determine the degree of total HjTBAQ conversion and conversion of H2TBAQ to TBAQ and hydrogen. The results are set forth in the table below.
TABLE OF RESULTS
Run Catalyst H2TBAQ Conversion (mole%)
No. System Total To TBAO
1 A 100 53
2 B 95 32
3 C 21 0
Run 1 demonstrates the enhanced performance of a catalyst system of the present invention for selectively converting H2TBAQ to TBAQ and hydrogen. The catalyst system of run 1 has a pretreated catalyst support as compared to the prior art catalyst systems of runs 2 and 3 having untreated catalyst supports.
EXAMPLE 2 An analytical procedure is performed on a pair of catalyst support samples to determine the relative acidities of the two samples. Sample 1 is an alumina catalyst support treated in accordance with the process of the present invention, placing lanthanum oxide on the catalyst support. Sample 2 is an alumina catalyst support substantially identical to the catalyst support of Sample 1 , but lacking a lanthanum oxide treatment.
Each sample is initially contacted with ammonia to saturate the surface thereof. The ammonia saturated samples are then heated to drive off the adsorbed ammonia, while measuring the amount of ammonia desorbed as a function of temperature by a technique termed temperature programmed 96/33015 1 1 PC17US96/02532
desoφtion (TPD). The desorbed ammonia from each sample is collected in sulfuric add solutions and the solutions are titrated upon completion of the TPD runs to determine the total amount of desorbed ammonia from each sample. The results of the TPD runs are shown in the Figure, wherein a TPD profile for each sample is generated by plotting the intensity of the ammonia signal on the y-axis (which is proportional to the rate of ammonia desorption) against temperature on the x-axis. The amount of ammonia desorbed from the sample is a function of the amount of ammonia adsorbed onto the sample, which in turn is a function of the acidity of the sample. Accordingly, a sample having more ammonia desorbed therefrom is relatively more acidic than a sample having less ammonia desorbed therefrom.
The TPD profile of Sample 2 in the Figure shows that untreated alumina contains both weak and strong acid sites. The weak acid sites are evidenced on the TPD profile of Sample 2 by a temperature peak around 290°C, corresponding to a maximum desorption rate at this temperature. The strong acid sites are evidenced on the TPD profile of Sample 2 by a pronounced shoulder centered around 400 °C. The area under the TPD profile of Sample 2 is greater than that of Sample 1 indicating that the treated alumina desorbs less ammonia than the untreated alumina and is, therefore, less acidic than the untreated alumina Although the TPD profile of Sample 1 exhibits a temperature peak around 290°C corresponding to the temperature peak of Sample 2, indicating the presence of weak acid sites on Sample 1 , there are fewer such sites on Sample 1 as evidenced by a lower peak. The TPD profile of Sample 1 also does not exhibit the shoulder centered around 400 βC exhibited by the TPD profile of Sample 2, suggesting that treatment of the alumina catalyst support in the manner of the present invention substantially reduces the number of strong acid sites thereon.
The measured value of total ammonia desorbed from Sample 2 is 3.6 std cnf/g and the measured value of total ammonia desorbed from Sample 1 is 2.9 std cnf/g, confirming the findings of the TPD profiles that the present treatment process favorably reduces the acidity of the alumina catalyst support. EXAMPLE 3
An analytical procedure is performed on a pair of catalyst system samples to determine the relative acidities of the two samples. The first sample is a palladium catalyst on a γ-alumina support that has been prepared in accordance with the process of the present invention, pretreating the catalyst support by placing lanthanum oxide thereon. The second sample is a palladium catalyst on a γ-alumina support substantially identical to the treated catalyst support of the first sample, but lacking lanthanum oxide. The catalyst concentration of both samples is 0.5 % by weight. The lanthanum oxide concentration of the first sample is 7.0 % by weight.
A methanol dehydration reaction is carried out in the presence of each catalyst system sample at 300°C and the relative rates of dimethyl ether (DME) production for each sample are measured. A higher rate of DME production indicates the presence of more acid sites on the catalyst system because such sites are required for the dehydration reaction. DME production in the presence of the first sample is 1.5 mole %, while DME production in the presence of the second sample is 10.9 mole %. The results show that the catalyst system prepared by the process of the present invention has substantially fewer acid sites than a comparable catalyst system lacking lanthanum oxide on the catalyst support.
While the foregoing preferred embodiments of the invention have been described and shown, it is understood that alternatives and modifications, such as those suggested and others, may be made thereto and fall within the scope of the present invention.

Claims

We claim: 1. A process for preparing a dehydrogenation catalyst system to convert a hydroquinone to a corresponding quinone and hydrogen comprising: selecting a catalyst support from the group consisting of alumina and silica; placing a sufficient quantity of a rare earth metal oxide on said catalyst support to reduce the acidity thereof; selecting a catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof; and placing said catalyst on said catalyst support to form a catalyst system. 2. The process of claim 1 wherein said rare earth metal oxide is placed on said catalyst support by contacting said catalyst support with a corresponding rare earth metal salt in solution. 3. The process of claim 1 wherein said rare earth metal oxide is lanthanum oxide. 4. The process of claim 2 wherein said corresponding rare earth metal salt is lanthanum nitrate. 5. The process of claim 1 wherein said catalyst is platinum. 6. The process of claim 2 further comprising calcining said catalyst support after contacting said catalyst support with said rare earth metal salt. 7. The process of claim 1 further comprising calcining said catalyst support after placing said catalyst thereon. 8. The process of claim 1 wherein said catalyst is placed on said catalyst support by contacting said catalyst support with a solution of a corresponding catalyst metal salt. 9. A process for preparing a dehydrogenation catalyst system used to convert a hydroquinone to a corresponding quinone and hydrogen comprising: selecting a catalyst support from the group consisting of alumina and silica; 14
placing a sufficient quantity of a metal oxide on said catalyst support to reduce the acidity thereof by contacting said catalyst support with a corresponding metal salt in solution and calcining said catalyst support to convert said corresponding metal salt to said metal oxide, wherein said metal oxide is selected from the group consisting of rare earth metal oxides, alkaline earth metal oxides, alkali metal oxides, and mixtures thereof, and said corresponding metal salt is selected from the group consisting of rare earth metal salts, alkaline earth metal salts, alkali metal salts, and mixtures thereof; selecting a catalyst from the group consisting of cobalt, nickel, the platinum group metals, and mixtures thereof; and placing said catalyst on said catalyst support by contacting said catalyst support with a solution of a corresponding catalyst metal salt to form a catalyst system. 10. The process of claim 9 further comprising calcining said catalyst system after placing said catalyst on said catalyst support. 11. A process for treating a catalyst support of a catalyst used to convert a hydroquinone to a corresponding quinone and hydrogen comprising : selecting a catalyst support from the group consisting of alumina and silica; and placing a sufficient quantity of a rare earth metal oxide on said catalyst support to reduce the acidity thereof. 12. The process of claim 11 wherein said rare earth metal oxide is placed on said catalyst support by contacting said catalyst support with a corresponding rare earth metal salt in solution. 13. The process of claim 11 wherein said rare earth metal oxide is lanthanum oxide. 14. The process of claim 12 wherein said corresponding rare earth metal salt is lanthanum nitrate. 15. The process of claim 12 further comprising calcining said catalyst support after contacting said catalyst support with said corresponding rare earth metal salt. 16. A dehydrogenation catalyst system comprising : a catalyst support having a porous surface, said catalyst support selected from the group consisting of alumina and silica; a rare earth metal oxide positioned on said surface of said catalyst support in a quantity sufficient to reduce the acidity thereof; and a catalyst positioned on said surface of said catalyst support, said catalyst selected from the group consisting of cobalt, nickel, the platinum group metals, and mixtures thereof. 17. The catalyst system of claim 16 wherein said rare earth metal oxide is lanthanum oxide. 18. The catalyst system of claim 16 wherein said catalyst is platinum. 19. A process for catalytically converting a hydroquinone to a corresponding quinone and hydrogen comprising: selecting a catalyst support from the group consisting of alumina and silica; placing a sufficient quantity of a metal oxide selected from the group consisting of rare earth metal oxides, alkaline earth metal oxides, alkali metal oxides, and mixtures thereof, on said catalyst support to reduce the acidity thereof; selecting a catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof; placing said catalyst on said catalyst support to form a catalyst system; converting a hydroquinone in the presence of said catalyst system to hydrogen and a corresponding quinone of said hydroquinone. 20. The process of claim 19 wherein said metal oxide is a rare earth metal oxide. 21. The process of claim 19 wherein said hydroquinone is selected from the group consisting of anthrahydroquinones, naphthahydroquinones, benzohydroquinones, and mixtures thereof. 22. A process for produdng sulfur and hydrogen from hydrogen suifide gas comprising: reacting hydrogen suifide gas with a quinone to produce sulfur and a corresponding hydroquinone of said quinone; recovering said sulfur; and regenerating said quinone from said corresponding hydroquinone by contacting said hydroquinone with a catalyst system prepared by the steps comprising; selecting a catalyst support from the group consisting of alumina and silica; pladng a suffident quantity of a metal oxide selected from the group consisting of rare earth metal oxides, alkaline earth metal oxides, alkali metal oxides, and mixtures thereof, on said catalyst support to reduce the acidity thereof; selecting a catalyst from the group consisting of nickel, cobalt, the platinum group metals, and mixtures thereof; and pladng said catalyst on said catalyst support to form said catalyst system. 23. The process of daim 22 wherein said metal oxide is a rare earth metal oxide. 24. The process of daim 22 wherein said quinone is selected from the group consisting of anthraquinones, naphthaquinones, benzoquinones, and mixtures thereof.
PCT/US1996/002532 1995-04-18 1996-02-22 Pretreatment of catalyst support to enhance catalytic dehydrogenation of a hydroquinone WO1996033015A1 (en)

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EP1031377A3 (en) * 1999-02-26 2001-06-27 dmc2 Degussa Metals Catalysts Cerdec AG Catalytic material and method for its preparation
US8105969B2 (en) * 2008-12-29 2012-01-31 Fina Technology Inc. Catalyst with an ion-modified binder
WO2020091418A1 (en) * 2018-10-31 2020-05-07 에스케이이노베이션 주식회사 Cobalt-based monoatomic dehydrogenation catalyst and method for preparing olefin corresponding to paraffin from paraffin by using same
KR20200049209A (en) * 2018-10-31 2020-05-08 에스케이이노베이션 주식회사 Cobalt-based Single-atom Dehydrogenation Catalysts and Method for Producing Corresponding Olefins from Paraffins Using the Same
KR102563207B1 (en) 2018-10-31 2023-08-02 에스케이이노베이션 주식회사 Cobalt-based Single-atom Dehydrogenation Catalysts and Method for Producing Corresponding Olefins from Paraffins Using the Same
US12161999B2 (en) 2018-10-31 2024-12-10 Sk Innovation Co., Ltd. Cobalt-based single-atom dehydrogenation catalysts and method for producing corresponding olefins from paraffins using the same
US20210402379A1 (en) 2020-06-25 2021-12-30 Sk Innovation Co., Ltd. Cobalt-Based Single-Atom Dehydrogenation Catalysts Having Improved Thermal Stability and Method for Producing Olefins From Corresponding Paraffins by Using the Same
US11766664B2 (en) 2020-06-25 2023-09-26 Sk Innovation Co., Ltd. Cobalt-based single-atom dehydrogenation catalysts having improved thermal stability and method for producing olefins from corresponding paraffins by using the same
US12064750B2 (en) 2020-09-17 2024-08-20 Sk Innovation Co., Ltd. Cobalt-based single-atom dehydrogenation catalysts having high selectivity and regenerability and method for producing corresponding olefins from paraffins using the same

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