JP7236241B2 - Ester manufacturing method - Google Patents

Description

The present invention relates to a method for producing esters.

Baeyer-Villiger oxidation (hereinafter referred to as BV oxidation) is known as a method for producing an ester by oxidizing a ketone. In BV oxidation, organic peracids such as performic acid, peracetic acid and m-chloroperbenzoic acid are generally used as oxidizing agents (see, for example, Non-Patent Document 1). However, since organic peracids have high impact sensitivity and are explosive, it is not preferable from the standpoint of risk management to apply an organic peracid as an oxidizing agent for BV oxidation in ester production on an industrial scale. As a method that does not use an organic peracid, for example, there is a method in which oxygen, which is easy to handle, is used as an oxidizing agent to promote BV oxidation in the presence of an aldehyde to produce an ester. Various complexes (see, for example, Patent Document 1 and Non-Patent Document 2) and metal oxides (see, for example, Patent Documents 2 and 3 and Non-Patent Document 3) are used as catalysts for ketone oxidation reactions in the presence of aldehydes. system has been reported. Among these, solid catalysts typified by metal oxides are industrially preferable from the standpoint of separation and purification of products and catalysts after the reaction.

JP-A-7-61982 JP-A-6-25083 JP-A-5-310721

Green Chem. , 2013, 15, 3332. Chem. Lett. , 1991, 641. Appl. Organometal. Chem. , 2015, 29, 450.

However, even in existing solid catalyst systems, there are restrictions on reaction conditions such as solvent and supplied oxygen concentration. For example, Non-Patent Document 3 discloses a BV oxidation reaction of ketones with an Fe—Sn catalyst in a pure oxygen atmosphere, and in this catalyst system, the reaction rate decreases as the oxygen supply rate decreases. Therefore, the BV oxidation reaction described in Non-Patent Document 3 is desirably performed in a pure oxygen atmosphere. However, handling combustible organic compounds under pure oxygen, which has a strong combustion-supporting property, is not preferable from the standpoint of risk management, as is the case with BV oxidation with organic peracids. Also, from the viewpoint of raw material procurement, a catalyst system using air as an oxidizing agent instead of pure oxygen is industrially preferable.

Furthermore, it is known that a halogen-based solvent is most suitable for the BV oxidation reaction. For example, Non-Patent Document 3 discloses a method for promoting the BV oxidation of cyclohexanone in the presence of dichloroethane solvent, but the catalytic activity of this catalyst system decreases in non-halogen solvents. Therefore, the BV oxidation reaction described in Non-Patent Document 3 is desirably performed using a halogen-based solvent. However, halogen-based solvents have a high burden on the human body and the environment, making it difficult to use them on an industrial scale.

The present invention provides a method for producing an ester (including a lactone) in a high yield, for example, in a method for producing an ester in which the reaction is carried out in the presence of a ketone, air and a co-oxidizing agent in a non-halogen solvent. With the goal.

As a result of intensive studies to solve the above problems, the present inventors have found that gold and/or cerium are included in the BV oxidation reaction in which ketones and molecular oxygen are reacted in the presence of a co-oxidizing agent (e.g., aldehyde). Based on the finding that a catalyst (e.g., cerium oxide and/or nanoparticulate gold immobilized on cerium oxide) functions as a catalyst to promote the reaction, the corresponding ester is obtained in high yield. As a result, the inventors have completed the present invention.

That is, the present invention is as follows.
[1]
A process for producing an ester comprising reacting a ketone, molecular oxygen and a co-oxidant over a catalyst containing gold and/or cerium.
[2]
The method for producing an ester according to [1], wherein the gold is in the form of nanoparticles.
[3]
The method for producing an ester according to [2], wherein the nanoparticulate gold is prepared by a liquid phase reduction method.
[4]
The method for producing an ester according to any one of [1] to [3], wherein the co-oxidant is an aldehyde.
[5]
The ester according to any one of [1] to [4], wherein the raw material containing molecular oxygen has a molecular oxygen concentration of more than 0% by volume and 25% by volume or less when the raw material containing molecular oxygen is supplied in the step. manufacturing method.
[6]
The method for producing an ester according to any one of [1] to [5], wherein the ketone is a cyclic ketone having a cyclic structure in its molecule.
[7]
The method for producing an ester according to any one of [1] to [6], wherein the ketone is cyclohexanone.
[8]
The method for producing an ester according to any one of [1] to [7], wherein in the above step, a reaction solvent having a function of mixing the ketone and the co-oxidant at the reaction temperature is used.
[9]
The method for producing an ester according to any one of [1] to [8], wherein the reaction solvent in the step is a non-halogen solvent.
[10]
A method for producing a catalyst used in the method for producing an ester according to any one of [1] to [9],
A step of supporting a gold-containing compound on a cerium catalyst by a deposition precipitation method;
a step of reducing the supported gold-containing compound to obtain a catalyst containing gold and cerium;
A method for producing a catalyst comprising
[11]
The method for producing a catalyst according to [10], wherein the reduction is liquid phase reduction.
[12]
The method for producing a catalyst according to [10] or [11], wherein the gold-containing compound is reduced to gold nanoparticles.

According to the production method of the present invention, for example, an ester can be obtained in high yield by reacting a ketone with air in a non-halogen solvent. Furthermore, when the catalyst used in the present invention is solid, it can be easily separated from the reaction liquid after the reaction.

A mode for carrying out the present invention (hereinafter simply referred to as "this embodiment") will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

The method for producing an ester of the present embodiment includes a step of reacting a ketone, molecular oxygen and a co-oxidant with a catalyst containing gold and/or cerium.

[1] Catalyst The catalyst used in the method for producing an ester of the present embodiment is a catalyst containing gold and/or cerium. The gold contained in the catalyst is preferably in the form of nanoparticles, and the nanoparticulate gold is preferably prepared by a liquid phase reduction method. The catalyst used in the present embodiment is not particularly limited, but includes, for example, a cerium catalyst and a cerium composite gold nanoparticle catalyst that function as a heterogeneous catalyst that does not dissolve in the reaction solution in the BV oxidation reaction.

The cerium catalyst is preferably in a basic or acidic state. Examples of such cerium catalysts include, but are not limited to, cerium nitrate, cerium phosphate, cerium sulfate, cerium (III) oxide, cerium (IV) oxide, cerium carbonate, and cerium hydroxide. Among these, cerium (IV) oxide is preferable from the viewpoint of catalytic activity. Also, cerium may form a composite oxide with other metals.

The amount of gold supported on the cerium-complexed gold nanoparticle catalyst is preferably 0.5 to 50% by mass, more preferably 1 to 20% by mass, and still more preferably 1 to 5% by mass relative to the carrier. When producing this catalyst, it is preferable to use a chloride as a gold starting compound. The particle size of the gold nanoparticles is 1 to 200 nm, preferably 1 to 100 nm from the viewpoint of catalytic activity.

As a method for reducing gold, a vapor phase reduction method, a liquid phase reduction method, a calcination treatment, or the like can be used, but a liquid phase reduction method using sodium borohydride as a reducing agent is particularly preferable. As the raw material compound of cerium, it is preferable to use the compounds described as the specific examples of the cerium catalyst, but it is particularly preferable to use cerium oxide as a carrier from the viewpoint of catalytic activity.

[2] Raw Material In the method for producing an ester of the present embodiment, a ketone is used as a raw material.

（式中、Ｒ₁及びＲ₂は同一又は異なって、置換基を有していてもよい炭化水素基を示す。Ｒ₁、Ｒ₂は互いに結合して、式中に示されるカルボニル基とともに環を形成していてもよい。）
で表される化合物が挙げられる。前記Ｒ₁、Ｒ₂における炭化水素基としては、特に限定されないが、例えば、脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、及びこれらの基が２以上結合した基が含まれる。このような化合物としては、特に限定されないが、例えば、シクロペンタノン、シクロヘキサノン、シクロへプタノン、シクロオクタノン、２－ブタノン、２－ペンタノン、３―ペンタノン、２－ヘキサノン、３－ヘキサノン、２－ヘプタノン、３－ヘプタノンがある。本実施形態に用いるケトンは、分子内に環状構造を有する環状ケトンであることが好ましい。この中でも、生成物の安定性の点からシクロヘキサノンが好ましい。 The raw material ketone is not particularly limited, but for example, the following formula (1)

(In the formula, R ₁ and R ₂ are the same or different _and represent _a hydrocarbon group which may have a substituent. may form
The compound represented by is mentioned. The hydrocarbon group for R ₁ and R ₂ is not particularly limited, but examples include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group in which two or more of these groups are bonded. included. Examples of such compounds include, but are not limited to, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, 2- There are heptanone and 3-heptanone. The ketone used in this embodiment is preferably a cyclic ketone having a cyclic structure in its molecule. Among these, cyclohexanone is preferable from the viewpoint of product stability.

A co-oxidizing agent is used in the method for producing an ester of the present embodiment.

（式中、Ｒ₃は置換基を有していてもよい炭化水素基を示す。）
で表される化合物が挙げられる。前記Ｒ₃における炭化水素基としては、特に限定されないが、例えば、脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基、及びこれらの基が２以上結合した基が含まれる。この中でも、アルデヒドの反応性の点から、芳香族水素基を有するカルボニル化合物、例えば、ベンズアルデヒドが好ましい。 The co-oxidant used in this embodiment is a hydrocarbon compound that undergoes autoxidation, which is a spontaneous reaction with molecular oxygen. Examples of the co-oxidizing agent include, but are not particularly limited to, aldehydes, branched alkanes, cyclic alkanes, and the like. Among these, aldehydes are preferred from the viewpoint of reactivity. The aldehyde used in this embodiment is not particularly limited, but for example, the following formula (2)

(In the formula, R ₃ represents a hydrocarbon group which may have a substituent.)
The compound represented by is mentioned. The hydrocarbon group for R ₃ is not particularly limited, but includes, for example, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group in which two or more of these groups are bonded. Among these, carbonyl compounds having an aromatic hydrogen group, such as benzaldehyde, are preferred from the viewpoint of the reactivity of aldehydes.

The raw material (oxygen source) containing molecular oxygen used in this embodiment is preferably air. As the raw material containing molecular oxygen, pure oxygen or one with an arbitrarily diluted oxygen concentration can be used. It is preferable that the concentration of molecular oxygen in the raw material is more than 0% by volume and 25% by volume or less. Furthermore, from the viewpoint of raw material supply, it is particularly preferable to use air.

[3] Solvent It is preferable that the above steps in the method for producing an ester of the present embodiment are performed in the presence of a reaction solvent. Among them, it is preferable to use a reaction solvent capable of mixing the ketone and the co-oxidant at the reaction temperature in the above step. Moreover, as the reaction solvent in the above step, it is preferable to use a non-halogen solvent containing no halogen element. Examples of the reaction solvent include, but are not limited to, water, hydrocarbon solvents (e.g., toluene, benzene, xylene, pentane, hexane), ether solvents (e.g., tetrahydrofuran, dioxane), alcohol solvents (e.g., ethylene glycol, ethanol, methanol, t-butanol), carbonyl solvents (eg, ethyl acetate, dimethylacetamide, acetamide, dimethylformamide, N-methylpyrrolidone) and the like. Among these, a reaction solvent that is resistant to an oxidation reaction is preferred, and specific examples include, but are not particularly limited to, ethyl acetate.

[4] Reaction Conditions In the above step, the amount of catalyst used is preferably 0.05 g to 1.0 g per 1 g of ketone (eg, cyclohexanone) from the viewpoint of reaction rate and catalyst separation after reaction. 0 g, more preferably 0.05 g to 0.8 g, still more preferably 0.1 g to 0.5 g.

In the above step, the amount of the co-oxidizing agent (eg, aldehyde) is preferably 0.5 equivalents to 10 equivalents, more preferably 1 0 equivalent to 4.0 equivalents, more preferably 2.0 equivalents to 3.0 equivalents.

In the above step, the reaction temperature is preferably about 10°C to 250°C, more preferably about 30°C to 180°C, even more preferably about 30°C to 120°C.

The above reaction can be carried out, for example, by a conventional method such as a batch system, a semi-batch system, or a continuous system.

After completion of the reaction, the reaction product, the ester, can be separated and purified by separation means such as concentration, distillation, extraction, crystallization, recrystallization, or a combination of these separation means.

[5] Method for producing a catalyst The method for producing a catalyst of the present embodiment is a method for producing a catalyst used in the above-described method for producing an ester, comprising a step of supporting a gold-containing compound on a cerium catalyst by a deposition-precipitation method; reducing the supported gold-containing compound to obtain a catalyst containing gold and cerium. As a reduction method, a vapor phase reduction method, a liquid phase reduction method, a calcination treatment, or the like can be used, and the liquid phase reduction method is particularly preferable. The reducing agent used in the liquid phase reduction is not particularly limited, and examples thereof include sodium borohydride and lithium aluminum hydride. Among them, sodium borohydride is preferred. The amount of gold supported on the catalyst is preferably 0.5 to 50% by mass, more preferably 1 to 20% by mass, and still more preferably 1 to 5% by mass relative to the carrier. When producing this catalyst, it is preferable to use a chloride as the gold-containing compound. Specific examples include, but are not particularly limited to, chloroauric acid. In the method for producing the catalyst of the present embodiment, it is preferable to convert the gold-containing compound into gold nanoparticles by reduction. The particle size of the nanoparticle gold is 1 to 200 nm, preferably 1 to 100 nm from the viewpoint of catalytic activity.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples described below.

[Example 1]
Catalyst preparation: 2.0 g of cerium oxide (CeO ₂ ) and 100 g of ion-exchanged water were added to a glass eggplant flask, and 1.0 mL of 0.5 M chloroauric acid solution and 5 mL of 10% aqueous ammonia were successively added dropwise. A gold precursor was supported on cerium oxide by a deposition-precipitation method. The solid content was recovered from the resulting suspension by filtration, and the supported gold hydroxide was treated with sodium borohydride (liquid phase reduction method) to obtain a cerium composite gold nanoparticle catalyst (Au/CeO ₂ ) was prepared. At this time, it was found that the gold contained in the present catalyst was in the form of nanoparticles because the catalyst powder exhibited a purple color derived from the surface plasmon of the gold nanoparticles.
Reaction: 0.1 g of the cerium-composite gold nanoparticle catalyst (Au/CeO ₂ ) prepared above, 10.0 g of ethyl acetate, 0.4 g of cyclohexanone, and 1.3 g of benzaldehyde were added to a glass eggplant flask, and air was bubbled. , and stirred at 80°C for 3 hours to obtain caprolactone. The conversion rate of cyclohexanone and the yield of caprolactone were measured by an internal standard method using gas chromatography under the following analysis conditions. Table 1 summarizes the results.
(Analysis conditions)
Apparatus: Shimadzu gas chromatography GC2010
Column: CBP10
conditions:
・Injection temperature: 250°C, Detection temperature: 250°C
Carrier gas: nitrogen (column flow rate 1.59 mL/min, SP ratio 200)
・Temperature increase rate: 60°C (5 minutes hold) ~ (10°C/min) ~ 100°C ~ (10°C/min) ~ 250°C (5 minutes hold)
Internal standard: dibutyl ether

[Example 2]
Example 2 was carried out in the same manner as in Example 1, except that the reaction time was changed to 5 hours. The results are summarized in Table 1.

[ Reference example 1 ]
Reference Example 1 was carried out in the same manner as in Example 1, except that the cerium composite gold nanoparticle catalyst (Au/CeO ₂ ) was changed to cerium oxide (CeO ₂ ). The results are summarized in Table 1.

[Example 4]
Example 4 was carried out in the same manner as in Example 1, except that the reaction temperature was changed to 40°C. The results are summarized in Table 1.

[ Reference example 2 ]
Reference Example 2 was carried out in the same manner as in Example 1, except that the gold reduction method was changed from liquid phase reduction to calcination treatment (300° C., 3 hours). The results are summarized in Table 1. From this result, it can be seen that the liquid phase reduction method is particularly effective as a method for producing a cerium-composite gold nanoparticle catalyst.

[Example 6]
Example 6 was carried out in the same manner as in Example 1, except that cyclohexanone was changed to cyclopentanone. At this time, the conversion of cyclopentanone was 85%, and valerolactone was obtained in a yield of 80%.

[Comparative Example 1]
Comparative Example 1 was carried out in the same manner as in Example 1, except that it was carried out without a catalyst. The yield of caprolactone decreased under the condition of not adding a catalyst (cyclohexane conversion: 21%, caprolactone yield: 19%).

[Comparative Example 2]
Comparative Example 2 was carried out in the same manner as Example 1 except that it was carried out without the co-oxidant. Caprolactone was not produced under the conditions where no co-oxidant was added (cyclohexane conversion: 0%, caprolactone yield: 0%). In other words, a co-oxidizing agent is essential in the present invention.

[Comparative Example 3]
Comparative Example 3 was carried out in the same manner as in Example 1, except that molecular oxygen was not supplied. No caprolactone was produced under the condition that molecular oxygen was not added (cyclohexane conversion: 0%, caprolactone yield: 0%). In other words, molecular oxygen is essential in the present invention.

INDUSTRIAL APPLICABILITY The present invention is suitable as a method for producing an ester because, for example, an ester can be obtained by using a solid catalyst system that exhibits high activity in the BV oxidation reaction of ketones without the need to supply a halogen-based solvent or pure oxygen. .

Claims (10)

A step of reacting a ketone, molecular oxygen and a co-oxidant with a heterogeneous catalyst containing gold and/or cerium, wherein the heterogeneous catalyst is a cerium-complexed gold nanoparticle catalyst, and the gold is a nanoparticle. and wherein said nanoparticulate gold is prepared by a liquid phase reduction method . 2. The method for producing an ester according to claim 1 , wherein said co-oxidizing agent is an aldehyde. 3. The method for producing an ester according to claim 1 or 2 , wherein the raw material containing molecular oxygen has a molecular oxygen concentration of more than 0% by volume and 25% by volume or less when the raw material containing molecular oxygen is supplied in the step. The method for producing an ester according to any one of claims 1 to 3 , wherein the ketone is a cyclic ketone having a cyclic structure in its molecule. The method for producing an ester according to any one of claims 1 to 4 , wherein the ketone is cyclohexanone. 6. The method for producing an ester according to any one of claims 1 to 5, wherein in said step, a reaction solvent having a function of mixing the ketone and the co-oxidant at the reaction temperature is used. The method for producing an ester according to any one of claims 1 to 6 , wherein the reaction solvent in said step is a non-halogen solvent. A method for producing a catalyst used in the method for producing an ester according to any one of claims 1 to 7 ,
A step of supporting a gold-containing compound on a cerium catalyst by a deposition precipitation method;
a step of reducing the supported gold-containing compound to obtain a catalyst containing gold and cerium;
A method for producing a catalyst comprising 9. The method for producing a catalyst according to claim 8 , wherein the reduction is liquid phase reduction. 10. The method for producing a catalyst according to claim 8 or 9 , wherein the gold-containing compound is converted into gold nanoparticles by the reduction.