JPS5931489B2 - 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 used as an intermediate in the production of polyester, which is the raw material for urethane polymers.
It is an industrially important substance.

The reaction of co-oxidizing cyclohexanones and aldehydes with molecular oxygen to obtain ε-caprolactone and carboxylic acids is already known, and a related patent is US Pat.
There are No. 5306, 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, and therefore has a low aldehyde utilization efficiency. [Phase] U.S. Pat. No. 3,483,222 discloses ferric chloride as a catalyst,
Methods using soluble iron compounds such as ferric acetate and iron acetonyl acetate have been disclosed.

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 mo9bdenum compound and a nitrogen-containing heterocyclic compound is an excellent catalyst that can reduce 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 a soluble iron compound and molybdenum as catalysts. The present invention relates to a method for simultaneously producing ε-caprolactone and carboxylic acids, which is characterized in that a compound having a heterocyclic ring l containing at least one nitrogen atom and acting as a polydentate ligand is used in combination.

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, R 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, propionaldehyde, 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, An inert organic solvent 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; and nitriles such as acetonitrile and benzonitrile. . The oxidation reaction of the present invention is carried out using molecular oxygen as an oxidizing agent.

Molecular oxygen includes pure oxygen, air, air with increased oxygen concentration,
It is supplied in the form of a mixed gas consisting of oxygen and an inert gas (carbon dioxide, nitrogen, etc.). Reaction temperature is -20~150
Selected from the range of °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/Cli. The novel catalyst system, which is a feature of the method of the present invention, has a soluble iron compound, a soluble molybdenum compound, and a heterocycle containing at least one nitrogen atom, and acts as a polydentate ligand, and has the following general formula () (In the formula, R1 and R2 are hydrogen atoms, carbon atoms 1 to
4 alkyl group or an aryl group having 6 to 10 carbon atoms.

), 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 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 soluble molybdenum compounds as long as they are soluble in the reaction system, and specific examples thereof include molybdenyl naphthenate, molybdenyl acetylacetonate, molybdenum hexacarbonyl, molybdenyl citrate, phosphomolybdic acid, and silicon molybdic acid. etc.

It also has a heterocycle containing at least one nitrogen atom,
Preferably, the compound that acts as a polydentate ligand has an α-diimine structure of -H-CH-CH-N, and includes, for example, a substance having the following structural formula.

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 R4 represent a hydrogen atom or an alkyl group (preferably having 6 to 10 carbon atoms). represents a carbon number (1 to 4), an aryl group (preferably a carbon number of 6 to 10), a nitro group, or a halogen atom.

Specific examples of suitable compounds include 2,2/-bipyridyl, 4,4'-dimethyl-2,2'-bipyridyl, 1,
10-phenanthroline, 4,7-dimethyl 1,10-
Phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 4-nitro-1,10-phenanthroline, 4-chloro-1,10-phenanthroline, and the like. Particularly preferred compounds are 2,2'-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 molybdenum compound is used in such a manner that the molybdenum concentration is 0.1 to 100 ppm, preferably 1 to 50 ppm, based on the weight of the reaction mixture. Note that it is desirable to maintain the concentration of molybdenum 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 0.1 to 1000 ppm, preferably 1 to 50 ppm.

The ratio of the nitrogen-containing heterocyclic compound to the iron and molybdenum atoms is not particularly limited, but usually about 1 to 5 moles of the nitrogen-containing heterocyclic compound are used per 1 mole of the total amount of iron and molybdenum. is preferred.

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 the excess raw material, the ε-caprolactone and the 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 addition, in the following examples and comparative examples, unless otherwise specified, "%" means mol%, "Ppm"
represents weight Ppm.

Examples 1 to 7 Iron naphthenate monophosphorus molybdic acid-2,2'-pipyridyl catalyst system 90 ml of cyclohexanone (a) was charged into a 300 ml glass flask, and heated for 20 minutes while maintaining the temperature at 50°C.
Weight 88% acetaldehyde-cyclohexanone (5)
50 ml of the solution was added over a period of 2 hours, while air was blown at a flow rate of 151/Hr while stirring vigorously.

The catalyst was dissolved in cyclohexanone ((a) 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
where the concentration of catalyst is Ppm by weight relative to the reaction mixture
For metal compounds, it is expressed by 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 to obtain the results shown in Table 1.

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 these results, 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 molybdenum 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 form ε-caprolactone. The following general formula (I
I) R'-CO_2H (II) (In the above general formula (II), R' is as defined in the above general formula (I).) When producing carboxylic acids represented by There are soluble iron compounds and molybdenum compounds as well as the following general formula (III) ▲ mathematical formula, chemical formula, table, etc. ▼ ( III) (wherein, 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. ) A method for simultaneously producing caprolactone and carboxylic acids, characterized by using a compound represented by: 2. The manufacturing method according to claim 1, wherein the aldehyde is acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, hexanal, or 2-ethylhexanal. 3. The production method according to claim 1, wherein the compound having a heterocycle containing at least one nitrogen atom and serving 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 production method according to claim 1, wherein the concentration of the soluble molybdenum compound is 0.1 to 100 ppm as molybdenum based on the weight of the reaction mixture. 6. The compound 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 0.1 to 1000 ppm based on the weight of the reaction mixture. Manufacturing method. 7 Claim 1 in which the reaction temperature is 20 to 60°C
Manufacturing method described in section.