JPS5931490B2 - Simultaneous production method of ε-caprolactone and carboxylic acids - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for simultaneously producing ε-caprolactone and carboxylic acids.

More specifically, the present invention relates to an improvement in a method for co-oxidizing cyclohexanone and aldehydes with molecular oxygen to produce ε-caprolactone and carboxylic acids corresponding to the aldehydes. ε-caprolactone is an industrially important substance as an intermediate in the production of polyester, which is a raw material for urethane polymers.

The reaction of co-oxidizing cyclohexanones and aldehydes with molecular oxygen to obtain ε-caprolactones and carboxylic acids is already known, and related patents include US Pat.
There are No. 25306, No. 3483222, etc.

US Pat. No. 3,025,306 discloses a method in which the above reaction is carried out in the presence of cobalt, manganese, etc. However, this method has the drawback that it produces many oxidative decomposition products such as adipic acid, and also produces a large amount of carboxylic acid, so that the aldehyde utilization efficiency 2 is low. US Pat. No. 8,483,222 discloses a method using soluble iron compounds such as ferric chloride, ferric acetate, and iron acetonyl acetate as catalysts.

However, this method has low catalytic activity and low industrial value. The present inventors are searching for a more efficient catalyst for the above co-oxidation method with the aim of producing ε-caprolactone at a high yield, high selectivity, and at low cost. The present invention has been achieved by discovering that a ternary system of a tungsten compound and a nitrogen-containing heterocyclic compound is an excellent catalyst that reduces the production ratio of carboxylic acid while maintaining a sufficient oxygen absorption rate. .

That is, the gist of the present invention is to co-oxidize a mixture of cyclohexanone and aldehydes with molecular oxygen to produce ε-caprolactone and carboxylic acids corresponding to the aldehydes, using soluble iron compounds and tungsten compounds as catalysts. , and the following general formula () having a heterocycle containing at least one nitrogen atom and serving as a polydentate ligand (wherein R1 and R2 are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a carbon number Represents 6 to 10 aryl groups.

), the following general formula () (wherein R3 and R4 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 10 carbon atoms, a nitro group or a halogen atom.

) The present invention relates to a method for simultaneously producing ε-caprolactone and carboxylic acids, which is characterized by using a compound represented by: To explain the present invention in detail, the method of the present invention is represented by the following reaction formula.

However, in the above reaction formula, k represents an alkyl group having 1 to 20 carbon atoms.

Specific examples of aldehydes (1) suitable as raw materials for the method of the present invention include acetaldehyde, fropionaldehyde, butyraldehyde, isobutyraldehyde, hexanal, 2-ethylhexanal, trimethylacetaldehyde, hexadecanal, and the like. .

Among these, preferred are acetaldehyde, propionaldehyde, butyraldehyde, and isobutyraldehyde.

Although the molar ratio of cyclohexanone and aldehydes is not particularly limited, it is usually preferable to use an excess of cyclohexanone.

In the reaction of the present invention, a solvent is not particularly required. For example, the raw materials cyclohexanone and aldehydes and/or the product carboxylic acids themselves may be used as solvents, but if necessary, Inert organic solvents may also be used.

Examples of such organic solvents include hydrocarbons such as hexane, cyclohexane and benzene; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and methyl benzoate; acetonitrile and benzonitriles. The oxidation reaction of the present invention is carried out using molecular oxygen as an oxidizing agent. Molecular oxygen includes pure oxygen, nitrogen, air oxygen with increased oxygen concentration, and inert gases (carbon dioxide, nitrogen, etc.)
It is supplied in the form of a mixed gas consisting of: The reaction temperature is -
The temperature is selected from the range of 20 to 150°C.

As the reaction temperature increases, the conversion rate of cyclohexanone increases, but at the same time, the yield of undesirable by-products such as adipic acid increases, so the selectivity for ε-caprolactone decreases. Taking these things into consideration, the preferred reaction temperature range is 10 to 80°C, more preferably 20 to 60°C. The reaction pressure is not critical, but is usually between atmospheric pressure and 3
Selected from the range 0k9/Cd. The novel catalyst system that characterizes the process of the invention consists of a soluble iron compound, a soluble tungsten compound, and a compound having a heterocycle containing at least one nitrogen atom and acting as a polydentate ligand.

The soluble iron compound is not particularly limited as long as it is soluble in the reaction system, but specific examples thereof include iron naphthenate, iron octylate, iron tolate, iron acetylacetonate, iron acetate, and the like. In addition, there are no particular limitations on the soluble tungsten compound as long as it is soluble in the reaction system, and specific examples include tungstenyl naphthenate, tungstenyl acetylacetonate, tungsten hexacarbonyl,
Examples include tungstenyl citrate, phosphotungstic acid, silicotungstic acid, borotungstic acid, and the like.

Moreover, as a compound having a heterocycle containing at least one nitrogen atom and functioning as a polydentate ligand, a compound having an α-diimine structure -N-CH-CH=N- is preferable, for example, Examples include substances having the structural formula as described below.

In the above structural formula, R1 and R2 represent a hydrogen atom, an alkyl group (preferably having 1 to 4 carbon atoms), or an aryl group (preferably having 6 to 10 carbon atoms), and R3 and & represent a hydrogen atom or an alkyl group (preferably having 6 to 10 carbon atoms). 1 to 4 carbon atoms), an aryl group (preferably 6 to 10 carbon atoms), a nitro group, or a halogen atom.

Specific examples of suitable compounds include 2,2''-bipyridyl, 4,4'-dimethyl-2-goubipyridyl, 1,1
0-phenanthroline, 4,7-dimethyl-1,10-
They include phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 4-0tro1,10-phenanthroline, 4-chloro-1,10-phenanthroline, and the like. Particularly preferred compounds are 2,21-bipyridyl and 1,10-phenanthroline. The soluble iron compound has a concentration of 0.00 as iron based on the weight of the reaction mixture.
It is used in an amount of 1 to 100 ppm, preferably 0.2 to 10 ppm.

The soluble tungsten compound has a concentration of 0.1 to 200 ppm1 based on the weight of the reaction mixture as tungsten.
It is preferably used in an amount of 2 to 100 ppm.
Note that it is desirable that the concentration of tungsten be maintained at a level equal to or higher than the concentration of iron. The concentration of the nitrogen-containing heterocyclic compound relative to the weight of the reaction mixture is, for example, 0.01 to 500 ppm, preferably 2 to 200 ppm when 2.2'-bipyridyl is used. The ratio of iron and tungsten atoms to the nitrogen-containing heterocyclic compound is not particularly limited, but usually the total amount of iron and tungsten is 1
It is preferable to use about 1 to 5 moles of the nitrogen-containing heterocyclic compound per mole. The method of the present invention can be carried out by either a batch method or a continuous method.

The reaction products are recovered according to conventional methods. for example,
After separating off excess raw material, ε-caprolactone and carboxylic acid are separated by distillation. The main advantages of the method of the present invention are (1) high yield of ε-caprolactone, (2) low production of undesirable by-products such as adipic acid, and (3) utilization of aldehydes. It is highly efficient.

Next, the method of the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In the Examples and Comparative Examples below, unless otherwise specified, "%" represents mol% and "Ppm" represents weight Ppm.

Examples 1 to 4 Iron naphthenate-phosphotungstic acid-2.2/bipyridyl catalyst system 90 ml of cyclohexanone (a) was charged into a 300 ml glass flask, and heated at 50°C for 20 minutes.
Weight x *Amount% Acetaldehyde-Cyclohexanone (b)
50 ml of solution was added using a metering pump over a period of 2 hours, and at the same time air was blown at a flow rate of 151/Hr while stirring vigorously.

The catalyst was dissolved in cyclohexanone (5a and (b) above) in advance so that the catalyst concentration remained unchanged during the reaction.

The concentration of the catalyst is as shown in Table-1. Furthermore, Table 1
The concentration of the catalyst is expressed in Ppm by weight relative to the reaction mixture, and the concentration of the metal compound is expressed as the concentration of metal atoms. After the addition of acetaldehyde was completed, the reaction was continued for another hour while blowing air, and the resulting product was analyzed by gas chromatography, and the results shown in Table 1 were obtained.

Comparative Example 1 The same operation as in Example 1 was performed except that the catalyst concentration was changed as shown in Table 1.

The results are shown in Table-1. ' From this result, it can be seen that a sufficient oxygen absorption rate cannot be obtained when an iron compound is not added.

Comparative Example 2 The same operation as in Example 1 was performed except that the catalyst concentration was changed as shown in Table 1.

The results are shown in Table-1. This result shows that the aldehyde utilization efficiency decreases when a tungsten compound is not added.

Claims (1)

[Claims] 1 Cyclohexanone and the following general formula (I) R'-CH
A mixture with an aldehyde represented by O(I) (in the above general formula (I), R' represents an alkyl group having 1 to 20 carbon atoms) is co-oxidized with molecular oxygen to produce ε-caprolactone and the following. General formula (II)
When producing carboxylic acids represented by R'-CO_2H(II) (in the above general formula (II), R' is as defined in the above general formula (I)), a soluble catalyst is used as a catalyst. iron compounds and tungsten compounds, as well as the following general formula (III), which has a heterocycle containing at least one nitrogen atom and acts as a polydentate ligand ▲ There are mathematical formulas, chemical formulas, tables, etc. In the formula, R_1
and R_2 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 10 carbon atoms. ), the following general formula (IV) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (IV) (In the formula, R_3 and R_4 are hydrogen atoms, alkyl groups with 1 to 4 carbon atoms, aryl groups with 6 to 10 carbon atoms,
Represents a nitro group or a halogen atom. ) characterized by the combined use of a compound represented by
Simultaneous production method of caprolactone and carboxylic acids. 2. The production method according to claim 1, wherein the aldehyde is acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, hexanal, 2-ethylhexanal, trimethylacetaldehyde, or hexadecanal. 3. The production method according to claim 1, wherein the compound having a heterocycle containing at least one nitrogen atom and acting as a polydentate ligand is 2,2'-bipyridyl or 1,10-phenanthroline. 4. The production method according to claim 1, wherein the concentration of the soluble iron compound is 0.001 to 100 ppm as iron based on the weight of the reaction mixture. 5. The manufacturing method according to claim 1, wherein the concentration of the soluble tungsten compound is 0.1 to 200 ppm as tungsten based on the weight of the reaction mixture. 6. The production according to claim 1, wherein the concentration of the compound having a heterocycle containing at least one nitrogen atom and acting as a polydentate ligand is 0.01 to 500 ppm based on the weight of the reaction mixture. Law. 7 Claim 1 in which the reaction temperature is 20 to 60°C
Manufacturing method described in section.