US20060036112A1

US20060036112A1 - Process for the production of carboxylic acids

Info

Publication number: US20060036112A1
Application number: US11/254,909
Authority: US
Inventors: Carlo Fumagalli; Francesco Minisci; Roberto Pirola
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-05-15
Filing date: 2005-10-21
Publication date: 2006-02-16
Also published as: EP1282591B1; ATE294770T1; DE60110582D1; JP2003533500A; AU2001262283A1; WO2001087815A3; EP1282591A2; ES2241826T3; US20030144549A1; DE60110582T2; US7012155B2; WO2001087815A2

Abstract

Aliphatic carboxylic acids of formulae (Ib) R¹—COOH (Ia) and R²—COOH wherein R¹is tertiary C_4-20-alkyl and R²together are —(CH₂)_n— with n=3 to 10, are produced by oxidizing an aliphatic or alicyclic ketone of the formula (II):

wherein R¹and R²are as defined above, with molecular oxygen in the presence of a soluble manganese (II) compound. The process has a high selectivity and is carried out under very mild conditions. It is especially useful for the production of dicarboxylic acids, such as, adipic acid, from cyclic ketones.

Description

The invention relates to a process for the production of carboxylic acids by the oxidation of aliphatic or alicyclic ketones.
Aliphatic carboxylic acids and their derivatives are compounds of particular industrial interest. In particular, dicarboxylic acids such as adipic acid, 1,8-octanedioic acid (suberic acid) or 1,12-dodecanedioic acid are valuable starting materials for the synthesis of polyamides and other polymeric materials.
Several syntheses of dicarboxylic acids starting from cyclic ketones are known in the art, some of them being performed on a commercial scale. The most commonly used oxidant is nitric acid, although some other oxidants have been investigated, too. The nitric acid oxidation has several drawbacks, resulting mainly from the corrosivity of nitric acid and the byproducts formed, in particular nitrous oxide which has been found to cause environmental problems.
The technical problem to be solved by the present invention was to provide a selective and high-yield process for the production of aliphatic carboxylic or dicarboxylic acids from aliphatic or cycloaliphatic ketones using a non-corrosive and environmentally friendly oxidant.
According to the present invention, this problem has been solved by the process of claim 1.
It has been found that aliphatic carboxylic acids of the general formulae
R¹—COOH (Ia)
and
R²—COOH (Ib)

wherein R¹is tertiary C_4-20-alkyl
and R²is selected from hydrogen and C_1-6-alkyl,
or R¹and R²together are —(CH₂)_n— with n=3 to 10,
can be prepared by oxidizing ketones of the general formula
wherein R¹and R²are as defined above,
with molecular oxygen in the presence of a soluble manganese(II) compound.

Here and hereinbelow, C_1-6-alkyl is to be understood as any linear or branched primary, secondary or tertiary alkyl group having 1 to 6 carbon atoms, in particular groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl and so on.
Tertiary C_4-20-alkyl is to be understood as any tertiary alkyl group having 4 to 20 carbon atoms, in particular groups such as tert-butyl (1,1-dimethylethyl) or tert-pentyl (1,1-dimethylpropyl).
The process according to the invention is applicable to the oxidation of open-chain (aliphatic) ketones as well as alicyclic ketones, the former yielding a pair of monocarboxylic acids and the latter yielding a dicarboxylic acid.
In a preferred embodiment, R¹and R²together are —(CH₂)_n— and n is an integer selected from 3, 4, 5, 6 and 10, corresponding to the alicyclic ketones cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone and cyclododecanone as starting materials and the dicarboxylic acids glutaric acid (1,5-pentanedioic acid), adipic acid (1,6-hexanedioic acid), pimelic acid (1,7-heptanedioic acid), suberic acid (1,8-octanedioic acid) and 1,12-dodecanedioic acid as products.
In another preferred embodiment, R¹is tert-butyl and R²is hydrogen, the starting material being methyl tert-butyl ketone and the products (Ia) and (Ib) pivalic acid and formic acid, respectively.
Preferably, the soluble manganese(II) compound is manganese(II) nitrate. Other manganese(II) salts such as manganese(II) acetate may also be used.
More preferably, manganese(II) nitrate is used in an amount of 0.1 of 4 mol %, based on the amount of ketone (II).
The conversion rate and selectivity of the oxidation may be further improved by adding at least one compound selected from the group consisting of nitric acid, soluble cobalt(II) compounds and soluble copper(II) compounds in an amount of 0.1 to 5 mol %, based on the amount of ketone (II).
Preferably, the oxidation reaction is carried out in a solvent comprising at least one C_2-5-alkanoic acid. More preferably, acetic acid is used as solvent.
In a preferred embodiment, the molecular oxygen is used either in essentially pure form or in a gaseous mixture containing up to 90 vol % of nitrogen, e. g., ordinary air. Preferably, the total pressure is about 1 bar (i. e., ambient pressure) to 20 bar, more preferably about 1 bar to 5 bar.
The reaction temperature is preferably 0° C. to 100° C., more preferably 20° C. to 70° C. As the oxidation is exothermic, external cooling may be necessary to avoid thermal excursions.
Preferably, the oxidation reaction is carried out in a solvent, the weight ratio solvent/ketone being from 4 to 20 (i. e., 4:1 to 20:1). Besides the preferred alkanoic acids, any solvent which is essentially inert under the reaction conditions may be employed.
The invention is further illustrated by the following non-limiting examples.

EXAMPLE 1

Adipic Acid

A solution containing 25 mmol of cyclohexanone, 0.5 mmol of manganese(II) nitrate, 0.5 mmol of cobalt(II) nitrate and 1.5 mmol of nitric acid in 25 ml of acetic acid was stirred for 5 h at 40° C. in an oxygen atmosphere under ambient pressure. Subsequently, the acetic acid was distilled off. The residue was found to consist mainly of adipic acid with some glutaric acid and a small amount of unreacted starting material. The conversion of cyclohexanone was found to be 97.5%, the selectivity of the oxidation to adipic acid being 93.4%.

EXAMPLES 2-8, COMPARATIVE EXAMPLES 1-3

Adipic Acid

The procedure of Example 1 was repeated with different catalysts (without addition of nitric acid) at 20° C. or 40° C. The conditions and results are shown in Table 1.

TABLE 1


Example No.	Catalyst [mmol]	Temperature [° C.]	Conversion [%]	Selectivity [%]

2	Mn(NO₃)₂/ 0.5	20	68.7	92.2
	Co(NO₃)₂/ 0.5
3	Mn(NO₃)₂/ 0.5	20	34.6	81.7
4	Mn(OAc)₂/ 0.5	20	9.1	83.1
5	Mn(NO₃)₂/ 0.5	40	90.6	89.1
	Co(NO₃)₂/ 0.5
6	Mn(OAc)₂/ 0.5	40	19.3	90.1
	Co(OAc)₂/ 0.5
7	Mn(NO₃)₂/ 0.5	40	91.6	89.5
	Cu(NO₃)₂/ 0.5
8	Mn(OAc)₂/ 0.5	40	17.1	91.2
	Cu(OAc)₂/ 0.5
C1	Co(NO₃)₂/ 0.5	20	6.2	80.3
C2	Co(OAc)₂/ 0.5	20	trace	—
C3	Cu(NO₃)₂/ 0.5	20	trace	—

EXAMPLE 9

Adipic Acid

The procedure of Example 1 was repeated using 50 mmol of cyclohexanone instead of 25 mmol. The conversion of cyclohexanone was 95.7%, the selectivity 91.8%.

EXAMPLE 10

Adipic Acid

The procedure of Example 1 was repeated using air at 5 bar instead of oxygen at 1 bar. The conversion of cyclohexanone was 95.7%, the selectivity 92.6%.

EXAMPLES 11-14

The procedure of Example 1 was repeated using several different ketones as starting materials and a reaction temperature of 60° C. The results are compiled in Table 2.

	TABLE 2


	Conversion		Selectivity

Example No.	Ketone	[%]	Product	[%]

11	Cyclopentanone	98.2	Glutaric acid	91.7
12	Cycloheptanone	99.1	Pimelic acid	92.6
13	Cyclooctanone	97.3	Suberic acid	93.4
14	Cyclododecanone	98.6	1,12-	92.3
			Dodecane-
			dioic acid

EXAMPLE 15

Pivalic Acid

The procedure of Example 1 was repeated using methyl tert-butyl ketone instead of cyclohexanone and 70° C. reaction temperature. The conversion was 89.6%, the selectivity 96.4%. Formic acid was formed as second product (Ib).

Claims

1. A process for the production of aliphatic carboxylic acids of the general formulae

R¹—COOH (Ia)

and

R²—COOH (Ib)

wherein R¹is tertiary C_4-20-alkyl

and R²is selected from hydrogen and C_1-6-alkyl,

or R¹and R²together are —(CH₂)_n— with n=3 to 10,

comprising oxidizing a ketone of formula

wherein R¹and R²are as defined above,

with molecular oxygen in the presence of a soluble manganese(II) compound.

2. The process of claim 1, wherein R¹and R²together are —(CH₂)_n— with n=3, 4, 5, 6 or 10.

3. (canceled)

4. The process of claim 3, wherein the soluble manganese (II) compound is manganese (II) nitrate.

5. The process of claim 4, wherein the amount of manganese (II) nitrate is 0.1 to 4 mol % with respect to the amount of ketone (II).

6. The process of claim 5, wherein at least one additive selected from the group consisting of nitric acid, soluble cobalt (II) compounds and soluble copper(II) compounds is used in an amount of 0.1 to 5 mol % with respect to the amount of ketone (II).

7. The process of claim 6, wherein the oxidation is carried out in a solvent comprising at least one C_2-5-alkanoic acid.

8. The process of claim 7, wherein the molecular oxygen is used in essentially pure form or in a gaseous mixture containing up to 90 vol % of nitrogen and the total pressure is about 1 to 20 bar.

9. The process of claim 8, wherein the reaction temperature is 0 to 100° C.

10. The process of claim 9, wherein a solvent is present in an amount corresponding to a weight ratio solvent/ketone of 4 to 20.

11. The process of claim 1, wherein the soluble manganese (II) compound is manganese (II) nitrate.

12. The process of claim 11, wherein the amount of manganese (II) nitrate is 0.1 to 4 mol % with respect to the amount of ketone (II).

13. The process of claim 12, wherein at least one additive selected from the group consisting of nitric acid, soluble cobalt (II) compounds and soluble copper (II) compounds, is used in an amount of 0.1 to 5 mol % with respect to the amount of ketone (II).

14. The process of claim 2, wherein the soluble manganese (II) compound is manganese (II) nitrate.

15. The process of claim 14, wherein the amount of manganese (II) nitrate is 0.1 to 4 mol % with respect to the amount of ketone (II).

16. The process of claim 15, wherein at least one additive selected from the group consisting of nitric acid, soluble cobalt (II) compounds and soluble copper (II) compounds, is used in an amount of 0.1 to 5 mol % with respect to the amount of ketone (II).

17. The process of claim 1, wherein the oxidation is carried out in a solvent comprising at least one C_2-5-alkanoic acid.

18. The process of claim 1, wherein the molecular oxidation is used in essentially pure form or in a gaseous mixture containing up to 90 vol % of nitrogen, and the total pressure is about 1 bar to 20 bar.

19. The process of claim 1, wherein the reaction temperature is 0 to 100° C.

20. The process of claim 15, wherein the reaction temperature is 20 to 70° C.

21. The process of claim 1, wherein a solvent is present in an amount corresponding to a weight ratio solvent/ketone of 4 to 20.

22. The process of claim 9, wherein the reaction temperature is 20 to 70° C.

23. The process of claim 1, wherein the reaction temperature is 20 to 70° C.

24. A process for the production of aliphatic carboxylic acids of formulae:

R¹—COOH (1a)

and

R²—COOH (1b)

wherein R¹and R²together are —(CH₂)_n— and n is 3 to 10,

consisting of oxidizing a ketone of formula:

wherein R¹and R²are as defined above,

with molecular oxygen, in essentially pure form or in gaseous mixture with nitrogen, in the presence of a member selected from the group consisting of (a) a soluble manganese (II) salt, a soluble cobalt (II) salt and nitric acid, (b) a soluble manganese (II) salt and nitric acid, and (c) a soluble manganese (II) salt, a soluble copper (II) salt and nitric acid, and optionally in the presence of at least one solvent.