JP2001131112A - Method for simultaneously producing adipic acid and aromatic carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method without emitting harmful substances such as N2O, NOX, etc., in a method for producing adipic acid and an aromatic carboxylic acid. SOLUTION: An aromatic aldehyde and cyclohexane are cooxidized with molecular oxygen in the presence of a cobalt catalyst to produce the aromatic carboxylic acid and adipic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for simultaneously producing adipic acid and an aromatic carboxylic acid. Adipic acid is used as a raw material for various organic chemical products such as nylon-6,6 and urethane raw materials, plasticizers, and aromatic carboxylic acid is used as a raw material for various organic chemical products such as PVC stabilizers and plasticizers. .

[0002]

2. Description of the Related Art Adipic acid can be cyclohexanol alone or a mixture of cyclohexanol and cyclohexanone (K
/ A oil) with nitric acid (Chemtec, September 1974, p. 555-559).
This method requires expensive exhaust gas treatment equipment for treating N ₂ O and NOx generated by nitric acid oxidation. In addition, an aromatic carboxylic acid (for example, metatoluic acid) is produced by oxidizing an aromatic compound (for example, meta-xylene) substituted with a methyl group with air in the presence of a carboxyl group (Japanese Patent Application Laid-Open No. HEI 9-279516). 9-124
No. 548). The method of oxidizing with nitric acid has the same problems as described above, and the method of obtaining an aromatic carboxylic acid by air oxidation has a low yield.

Further, JP-A-10-286467 discloses that substrates (hydrocarbons, heterocyclic compounds) are present in the presence of an oxidation catalyst system comprising an imide compound and an element selected from Groups 3 to 12 of the periodic table. Compounds, alcohols, ketones, aldehydes, etc.) with oxygen to produce ketones, alcohols,
Methods for obtaining oxides such as aldehydes and carboxylic acids have been proposed. In this method, N generated by nitric acid oxidation
_Although the problem of the treatment of ₂ O and NOx can be solved, it is difficult to implement industrially due to the low reaction rate.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to produce adipic acid and aromatic carboxylic acids without producing expensive catalysts or harmful substances such as N ₂ O and NOx. It is to provide an industrially advantageous production method at a high speed.

[0005]

Means for Solving the Problems The present inventor has made intensive studies to achieve the above object, and found that aromatic aldehyde and cyclohexane are co-oxidized and co-oxidized with molecular oxygen to achieve an industrially feasible rate. The present inventors have found that adipic acid and an aromatic carboxylic acid can be obtained with good selectivity and have reached the present invention. That is, the present invention is a method for simultaneously producing adipic acid and aromatic carboxylic acid, wherein aromatic aldehyde and cyclohexane are co-oxidized with molecular oxygen to produce aromatic carboxylic acid and adipic acid.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the aromatic aldehyde used as a raw material in the present invention, benzaldehyde, o,
m, p-tolualdehyde, 2,4-dimethylbenzaldehyde, 2,5-dimethylbenzaldehyde, 3,4-dimethylbenzaldehyde, p-ethylbenzaldehyde, p-methoxybenzaldehyde, p-cuminaldehyde, biphenylaldehyde, n-butylbenzaldehyde , P-phenoxybenzaldehyde, 2,4,5-trimethylbenzaldehyde, 2,4,6-trimethylbenzaldehyde, 2,3,4-
Trimethylbenzaldehyde and the like.

[0007] These aromatic aldehydes are produced by industrially carrying out a Gattermann-Koch reaction formalizing an aromatic hydrocarbon into an aromatic aldehyde. And 2,4,5-trimethylbenzaldehyde is industrially produced on a large scale, and is suitably used as a raw material of the present invention. The aromatic carboxylic acids p-tolylic acid, dimethylbenzoic acid, 2,4,5-trimethylbenzoic acid and the like obtained therefrom can be used as they are, but p-tolylic acid is a terephthalic acid raw material and dimethylbenzoic acid. Is used as a raw material of trimellitic acid, and 2,4,5-trimethylbenzoic acid is also used as a raw material of pyromellitic acid.

In the present invention, the supply ratio of the aromatic aldehyde and cyclohexane to the reaction system is 0.0
1: 1 to 1: 1, preferably 0.03: 1 to 0.5: 1
Range. If the supply ratio of the aromatic aldehyde is further increased, the selectivity of the aromatic carboxylic acid decreases. Further, when the supply ratio of the aromatic aldehyde is further reduced, the oxidation rate of cyclohexane is reduced, and the yield of adipic acid and its intermediates (cyclohexanone and cyclohexanol) is reduced.

Molecular oxygen is used as an oxidizing agent for the co-oxidation reaction between the aromatic aldehyde and cyclohexane. The molecular oxygen is supplied in the form of pure oxygen, air, air with an increased oxygen concentration, a mixed gas of oxygen and an inert gas (carbon dioxide, nitrogen), and the like. In general, air is used. The reaction temperature ranges from 60 to 150 ° C, preferably from 80 to 130 ° C. If the reaction temperature is too low, the reaction rate will be low and the selectivity for adipic acid and its intermediates will be low. If the reaction temperature is too high, the selectivity of aromatic carboxylic acid and adipic acid will be low. The reaction pressure is preferably under pressure.
The conditions are selected within a range of 5 to 5 MPa so that the solvent maintains a liquid phase during the reaction. It is preferable that the oxygen partial pressure be in the range of 0.01 to 0.2 MPa.

[0010] The co-oxidation reaction of the present invention can be carried out without a catalyst. It is preferable to use a catalyst, and particularly a cobalt catalyst is suitably used. These metal catalysts can be used in the form of fatty acid salts such as naphthenate and stearate. The amount of the cobalt catalyst used is 1 ppm to 500 ppm, preferably 5 ppm, based on the total weight of the reaction solution.
３００300 ppm. If the amount of the cobalt catalyst used is too large, the selectivity of adipic acid and its intermediate decreases, and the number of side reactions increases. If the amount of the cobalt catalyst used is too small, the selectivity for adipic acid decreases. The residence time is 0.2-
10 hours, preferably in the range of 0.5 to 7 hours.

[0011] The co-oxidation reaction is usually carried out in the absence of a reaction solvent. However, a reaction solvent may be used if necessary.Hexanes, hydrocarbons such as benzene, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and methyl benzoate, acetonitrile, benznitrile, etc. And lower organic carboxylic acids such as formic acid, acetic acid, and propionic acid.

The reaction of the present invention can be carried out by any of a batch system, a semi-continuous system and a continuous system, but is preferably carried out by a semi-continuous system or a continuous system. The co-oxidation reaction solution according to the present invention contains cyclohexanone and cyclohexanol considerably. These are intermediates of adipic acid, which can be separated by distillation or the like and recycled to a co-oxidation reactor to increase the yield of adipic acid.

[0013]

Next, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by the following examples. In the following examples and comparative examples, “%” means “mol%” and “pp
"m" is a weight ratio. The reaction rate and selectivity are numerical values based on the following calculated values. Reaction rate = "Material reaction amount (mol)" / "Material supply amount (mol)" x 100% Selectivity = "Production amount (mol)" / "Material supply amount (mol)"
× 100%

Example 1 An autoclave having a stirrer content of 2 L and containing 98 ppm of cobalt as naphthenate as a catalyst was used as a catalyst.
400 g of a 10% 4-dimethylbenzaldehyde cyclohexane solution was charged, maintained at 1.4 Mpa and 120 ° C. in a nitrogen atmosphere, and air was introduced and the above 98 ppm was contained.
A cyclohexane solution containing 10% of 4-dimethylbenzaldehyde was supplied at 485 g / h. Oxygen concentration of off gas is 5vo
1% and supply was continued for 1 hour. Thereafter, the air was switched to nitrogen and cooled, and the reaction solution was extracted. As a result of analyzing the reaction solution, the 2,4-dimethylbenzaldehyde reaction rate was 93.
At 2%, the selectivity for 2,4-dimethylbenzoic acid was 93%. The cyclohexane conversion was 9%, the cyclohexanol selectivity was 11.1%, and the cyclohexanone selectivity was 35.1.
%, Adipic acid selectivity 39.9%, glutaric acid selectivity 6.5%, succinic acid selectivity 3.1%, and the total selectivity of adipic acid, cyclohexanone and cyclohexanol was 86.1%. .

Example 2 In Example 1, the concentration of 2,4-dimethylbenzaldehyde was 20%, the feed rate was 220 g / H, and the feed time was 1.5.
Time. As a result of analyzing the reaction solution, the conversion of 2,4-dimethylbenzaldehyde was 97.2%, and the selectivity for 2,4-dimethylbenzoic acid was 90%. The cyclohexane conversion is 1
6.7%, cyclohexanol selectivity 6.4%, cyclohexanone selectivity 21.5%, adipic acid selectivity 5
0.9%, glutaric acid selectivity 9.6%, succinic acid selectivity 4.1%, and the total selectivity of adipic acid, cyclohexanone and cyclohexanol was 78.8%.

Example 3 The reaction temperature in Example 1 was 160 ° C. As a result of analyzing the reaction solution, 2,4-dimethylbenzaldehyde conversion 9
At 8.6%, the selectivity for 2,4-dimethylbenzoic acid is 81.6%
Met. The cyclohexane conversion is 22.4%, cyclohexanol selectivity 7.1%, cyclohexanone selectivity 31.6%, adipic acid selectivity 28.2%, glutaric acid selectivity 7.3%, succinic acid selectivity 3 At 0.4%, the total selectivity of adipic acid, cyclohexanone and cyclohexanol was 66.9%. Increasing the reaction temperature causes a side reaction and lowers the selectivity of adipic acid.

Example 4 In Example 2, the reaction temperature was 100 ° C., and the supply time was 2
Time. As a result of analyzing the reaction solution, the conversion of 2,4-dimethylbenzaldehyde was 93.0%, and the selectivity for 2,4-dimethylbenzoic acid was 93%. The cyclohexane conversion is 1
At 4.3%, cyclohexanol selectivity 10.9%, cyclohexanone selectivity 41.7%, adipic acid selectivity 3
3.9%, glutaric acid selectivity 5.0%, succinic acid selectivity 2.4%, and the total selectivity of adipic acid, cyclohexanone and cyclohexanol was 86.5%.

Example 5 The procedure of Example 2 was repeated except that 5000 ppm of cobalt was used as the catalyst. As a result of analyzing the reaction solution, the conversion of 2,4-dimethylbenzaldehyde was 98.0%, and the selectivity for 2,4-dimethylbenzoic acid was 83%. The cyclohexane conversion was 18.3%, and the cyclohexanol selectivity was 1.9.
%, Cyclohexanone selectivity 8.7%, adipic acid selectivity 53.9%, glutaric acid selectivity 15.0%, succinic acid selectivity 7.4%, and the total selectivity of adipic acid, cyclohexanone and cyclohexanol is 64.5%. If the catalyst concentration is too high, the amount of by-products generated will increase.

[0019]

As is clear from the above examples, by co-oxidizing an aromatic aldehyde and cyclohexane with molecular oxygen according to the present invention, the corresponding aromatic carboxylic acid and adipic acid can be produced. By using a cobalt catalyst and adjusting the molar ratio of the aromatic aldehyde to cyclohexane, the reaction temperature, and the catalyst concentration, the yield of the target aromatic carboxylic acid and adipic acid can be increased. The method of the present invention oxidizes with an oxygen-containing gas that does not pollute the environment, and therefore does not generate harmful substances such as N ₂ O and NOx, and advantageously produces industrially useful adipic acid and aromatic carboxylic acids. Can be.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C07B 61/00 300 C07B 61/00 300

Claims (3)

[Claims] 1. A method for simultaneously producing adipic acid and aromatic carboxylic acid, comprising producing an aromatic carboxylic acid and adipic acid by co-oxidizing an aromatic aldehyde and cyclohexane with molecular oxygen. 2. The co-oxidation of an aromatic aldehyde and cyclohexane at a reaction temperature of 60 to 150 ° C. in the presence of a cobalt catalyst at a molar ratio of the aromatic aldehyde and cyclohexane to be supplied of 0.01: 1 to 1: 1. A method for simultaneously producing adipic acid and an aromatic carboxylic acid according to claim 1. 3. The reaction solution having a cobalt concentration of 1 to 500 pp.
3. The method for simultaneously producing adipic acid and an aromatic carboxylic acid according to claim 2, wherein the ratio is m (weight ratio).