JP2001233824A - Method for producing benzyl acetate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing benzyl acetate capable of fully exhibiting the performance of catalyst even by using a water-containing liquid as the reaction raw material. SOLUTION: Benzyl acetate is produced by contacting toluene, acetic acid, water and oxygen with a catalyst having acetoxylation performance. The amount of water for the reaction is set to <0.5 wt.% based on toluene and acetic acid used as the raw materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing benzyl acetate by reacting toluene, acetic acid and oxygen. For example, benzyl acetate itself is useful as a solvent or a fragrance, and benzyl alcohol obtained by hydrolyzing benzyl acetate is a solvent having excellent solubility, and is non-toxic, so it is a pharmaceutical additive. It is also a very important compound as an intermediate for agricultural chemicals and pharmaceuticals.

[0002]

2. Description of the Related Art It is known to produce benzyl acetate by reacting toluene, acetic acid and oxygen in the presence of a catalyst having acetoxylation ability. As such a catalyst, for example, JP-A-10-7616 discloses a catalyst in which palladium and bismuth are supported on silica. In addition, Japanese Patent Application Laid-Open No. H10-265637 discloses a catalyst in which palladium and antimony are supported on silica.

The reaction product obtained by the acetoxylation reaction contains by-product water, unreacted toluene and acetic acid, and it is necessary to efficiently recover and reuse these unreacted raw materials. It is economically advantageous. Recovery and separation of unreacted raw materials
Usually done by distillation. Specifically, the acetoxylation reaction product is separated into a gas phase portion mainly composed of oxygen and nitrogen of inert and a liquid phase portion mainly composed of toluene, acetic acid and benzyl acetate, and the liquid phase portion is separated by distillation. Then, there is a method in which a top fraction mainly containing toluene and acetic acid and a bottom liquid mainly containing benzyl acetate are separated, and the top fraction is recycled to an acetoxylation reaction raw material. At this time, a part of the water produced as a by-product of the acetoxylation reaction is contained in the overhead fraction and is circulated to the acetoxylation reaction, and the content of the water is several percent based on the toluene and acetic acid as the raw materials.

Further, as a method for producing benzyl alcohol from benzyl acetate, a method of hydrolyzing benzyl acetate (Japanese Patent Application Laid-Open No. 10-7608) and a method of transesterifying benzyl acetate with methanol (Japanese Patent Application Laid-Open No.
168007), and acetic acid produced as a by-product is recovered as an aqueous solution. If this acetic acid is used as a raw material for the acetoxylation reaction, there is a possibility that it will be economical and have a low environmental load. However, the vapor pressure difference between acetic acid and water in a high-concentration acetic acid aqueous solution is small, and it is extremely difficult to recover pure acetic acid by distillation. Normal,
In industrial distillation, water is several percent in recovered acetic acid
included.

[0005]

SUMMARY OF THE INVENTION In carrying out the present acetoxylation reaction, the present inventors affect the catalytic activity by the concentration of water contained in the reaction raw materials, and the higher the concentration of water, the better the activity of the catalyst. Was found to be impossible to express and maintain over a long period of time.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing benzyl acetate which can sufficiently exhibit the performance of a catalyst even if water in a reaction raw material liquid is contained. It is to provide.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the amount of water used for the reaction was reduced to less than 0.5% by weight based on the toluene and acetic acid as raw materials. As a result, the present inventors have found that a decrease in catalytic activity due to water can be avoided, and have completed the present invention.

That is, according to the present invention, in a method for producing benzyl acetate by contacting toluene, acetic acid, water and oxygen with a catalyst having acetoxylation ability, the amount of water used for the reaction is 0 to the starting toluene and acetic acid. Less than 0.5% by weight.

Hereinafter, the present invention will be described in detail.

In the method of the present invention, toluene and acetic acid are used as raw materials, and oxygen is used as an oxidizing agent. Toluene and acetic acid used as raw materials can be used as produced by any production method.For example, toluene separated from petroleum fraction or separated from cracked oil obtained by decomposing petroleum fraction can be used. What was done can be used. As the acetic acid, any of those produced by oxidation of acetaldehyde, those produced by oxidation of hydrocarbons, and those synthesized from methanol and carbon monoxide can be used. The raw material does not necessarily have to be pure, and can be used even if it contains impurities such as other hydrocarbon compounds that do not inhibit the reaction.

Further, as the toluene and acetic acid used as the raw materials, those recovered from the mixture after the completion of the acetoxylation reaction may be reused. Further, when benzyl acetate is hydrolyzed or transesterified with methanol to produce benzyl alcohol, acetic acid produced as a by-product can be recovered and used.

In the present invention, the amount of water to be subjected to the acetoxylation reaction must be less than 0.5% by weight based on the starting materials toluene and acetic acid. 0.5% by weight of water
When the temperature exceeds the above range, it is difficult to maintain good catalytic activity, and the selectivity for the target product, benzyl acetate, is lowered. Also,
When using the material recovered from the mixture after the completion of the acetoxylation reaction as the raw material, the recovered raw material always contains water. Usually 0.01-0.5% by weight
Is sufficient. When the recovered raw material is reused, the method for reducing the water content in the raw material to the above ratio is not particularly limited, and examples thereof include methods such as extractive distillation and azeotropic distillation. Can be

In the method of the present invention, molecular oxygen is used as an oxidizing agent. Oxygen may be diluted with an inert gas such as nitrogen, but it is preferable to use air in consideration of practicality.

In the process of the present invention, benzyl acetate is obtained by reacting toluene with acetic acid and oxygen in the presence of a catalyst having acetoxylation ability.

As the catalyst having acetoxylation ability, a catalyst capable of obtaining a desired reaction result can be used without any particular limitation. For example, a catalyst mainly composed of palladium having acetoxylation activity can be mentioned as a preferable example. Specifically, for example, in Japanese Patent Publication No. 42-13081,
A catalyst system comprising a catalyst in which palladium is supported on alumina and an alkali metal acetate is disclosed.

JP-A-52-151135 and JP-A-52-151136 disclose catalysts in which one selected from bismuth, molybdenum, manganese, vanadium and tungsten supported on silica is combined with palladium. Have been. Also, Japanese Patent Publication No. 50-2894
No. 7 discloses a catalyst system comprising a catalyst comprising one component selected from bismuth, cobalt and iron supported on silica, palladium, and potassium acetate. Further, Japanese Patent Publication No. 52-16101 discloses that silica has palladium,
A catalyst system comprising a bismuth and chromium supported catalyst and an alkali metal acetate is disclosed. In addition, Japanese Unexamined Patent Publication
JP-A-3-174950 discloses a catalyst system comprising both a catalyst in which palladium and bismuth or lead are supported on silica and a bismuth compound or lead compound which is soluble in the reaction system. Japanese Patent Application Laid-Open No. 10-7616 discloses a catalyst in which palladium and bismuth are supported on silica.

Further, JP-A-10-265437 discloses a catalyst in which palladium and antimony are supported on silica. In the present invention, these catalysts can be used without any particular trouble.

The form of the acetoxylation reaction is not particularly limited, and any form can be used as long as it can supply toluene, acetic acid, water and a predetermined concentration of oxygen as a raw material liquid and can contact the catalyst. . For example, a fixed bed circulation system, a batch system using a suspension bed, a semi-batch system, a continuous system, and the like can be used. However, in view of the productivity of benzyl acetate from an industrial point of view, a fixed bed circulation system is desirable.

The reaction according to the method of the present invention is carried out under heating and under pressure. The reaction temperature is usually selected from 80 to 230 ° C, preferably from 100 to 200 ° C. If it is higher than this, only the progress of the side reaction increases, and if it is lower, the reaction speed is disadvantageous. Further, the reaction pressure may be such that the surface of the catalyst is maintained in a liquid phase at the reaction temperature, and is usually 3 to 100 kg / c.
M2g, preferably selected is 4~50kg / cm ² G.

[0020]

Next, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to the following Examples. In addition, all the weight percentages in this embodiment are abbreviated as%.

Examples 1 and 2 and Comparative Examples 1 and 2 In an acetoxylation reactor made of SUS316 having an inner diameter of 41 mm,
2.67 liters of a catalyst in which palladium and antimony were supported on spherical silica were charged. In this reactor 1, a raw material solution containing water having a concentration shown in Table 1, 28.4 mol / h of industrial acetic acid,
28.4 mol / h of toluene and 447 NL / h of air were supplied, and the catalyst layer inlet temperature was 140 ° C. and the pressure was 0.76 MPa.
G was reacted. The reaction product was analyzed by gas chromatography to determine the space-time yield of benzyl acetate (the amount of benzyl acetate produced per unit catalyst volume per unit time).

[0022]

[Table 1]

In Table 1, the activity retention is expressed by the following equation.

[0024]

(Equation 1)

[0025]

The present invention relates to a method for producing benzyl acetate by bringing toluene, acetic acid, water and oxygen into contact with a catalyst having acetoxylation ability. The amount of water contained in the raw material was 0.5 to the amount of toluene and acetic acid of the raw material.
By making the amount less than% by weight, benzyl acetate can be industrially advantageously produced at a high selectivity without lowering the activity.

Claims (3)

[Claims] 1. A method for producing benzyl acetate by bringing toluene, acetic acid, water and oxygen into contact with a catalyst having acetoxylation ability, wherein the amount of water used for the reaction is 0.5 wt. % Of benzyl acetate. 2. The method according to claim 1, wherein the amount of water to be supplied to the reaction is 0.01 to 0.5% by weight based on toluene and acetic acid as raw materials. 3. The method according to claim 1, wherein the starting materials toluene and acetic acid are mainly composed of toluene and acetic acid recovered from a reaction product.