JP2662965B2 - Preparation of allyl acetate and allyl alcohol - Google Patents

Description

The present invention relates to a method for producing allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase, and then producing allyl alcohol by hydrolyzing the allyl acetate. Manufacturing method.

More specifically, when the unreacted raw material gas is circulated and used in order to improve the usage rate of the raw material, it is caused by partial hydrolysis of allyl acetate in the reaction product mixture gas generated by the gas phase reaction. Catalytic activity by controlling the concentration of allyl alcohol in the charged gas by keeping the concentration of allyl alcohol in the acetic acid used after circulating after separating allyl alcohol and the desired product of the hydrolysis process, aryl alcohol, And a process for producing allyl acetate and allyl alcohol, characterized in that

Allyl acetate is a monomer having a polymerizable double bond, and is used for copolymerizing with another monomer or used as a raw material for synthesizing allyl alcohol by hydrolysis.

[Conventional technology]

A method for producing allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase in the presence of a palladium catalyst is known. For example, Japanese Patent Publication No. 44-29046, Japanese Patent Publication No.
48-23408 and JP-B-50-28934 are known.

In these publications, palladium is applied to carriers such as alumina, silica, activated carbon, spinels, pumice or titanium oxide.
Allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase in the presence of a catalyst carrying 0.1 to 10% by weight, 1 to 20% by weight of an alkali metal or alkaline earth metal acetate and another metal. Are disclosed.

However, according to these techniques, the yield and selectivity of allyl acetate are low, and the catalyst activity is greatly reduced with time.

Japanese Patent Application Laid-Open No. 61-238759 discloses a technique for improving these disadvantages.
There is a method described in Japanese Patent Application Publication No.

According to the technique disclosed in this publication, a catalyst comprising palladium and an alkali metal acetate, for example, potassium acetate supported on a carrier made of silica, is used as a catalyst. Propylene gas is 12% by volume, oxygen is 7% by volume, Gaseous acetic acid 9
A mixed gas consisting of 72% by volume of nitrogen and 72% by volume of diluent gas was charged and reacted at 5 atm and a temperature of 140 ° C. to obtain allyl acetate with a space-time yield of 3.8 T / m ² · day.

In order to industrially obtain allyl acetate efficiently, in the above-mentioned conventional method, the unreacted propylene gas and acetic acid gas must be recycled to increase the lightening rate of the overall and to increase the usage rate of the raw materials. preferable.

It is also known to hydrolyze the allyl acetate produced as described above to produce allyl alcohol.

Therefore, the process of producing allyl acetate and the process of hydrolyzing it to produce allyl alcohol are often discussed in combination.

For example, the methods described in JP-A-61-238745, JP-A-60-258171 and the like are such.

[Object of the invention]

The present inventors industrially produce allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase in the presence of a palladium catalyst, and hydrolyze the allyl acetate thus produced to produce allyl alcohol. A method for preventing a decrease in the activity of the palladium catalyst for producing allyl acetate.

[Problems to be solved by the invention]

The present inventors have achieved the above-mentioned object, produced allyl acetate from propylene, oxygen and acetic acid by a gas phase reaction, and then studied intensively to produce the allyl alcohol industrially advantageously. It has been found that when a certain amount or more of allyl alcohol produced by the hydrolysis of allyl acetate is present in a total amount of the raw material gas mixed with the newly supplied raw material gas, the catalytic activity is reduced, and the present invention has been achieved.

[Means for solving the problem]

That is, the present invention provides a method of producing allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase in the presence of a palladium catalyst, and then hydrolyzing the allyl acetate.
Including unreacted propylene and acetic acid as the main components, and, when circulating a mixture containing a small amount of allyl alcohol through the reaction raw material gas and supplying it to the reaction, a charging stage to a distillation column for separating acetic acid and allyl alcohol, A method for producing allyl acetate and allyl alcohol, wherein the allyl alcohol concentration in the reaction raw material gas is adjusted to 100 ppm or less by adjusting the reflux ratio and the temperature in the distillation column.

Hereinafter, the method for producing allyl acetate and allyl alcohol of the present invention will be described in detail.

First, a mixed gas consisting of propylene, oxygen and acetic acid is passed in the gas phase in the presence of a palladium catalyst to produce allyl acetate, and the allyl acetate is hydrolyzed to produce allyl alcohol. Will be described in detail.

When synthesizing allyl acetate by passing a mixed gas consisting of propylene, oxygen, and acetic acid in the gas phase in the presence of a palladium catalyst, the rate of change of acetic acid, a component of the raw material gas, is relatively low. A method in which the crude liquid is distilled, allyl acetate is recovered from the top of the column, and unreacted acetic acid recovered from the bottom of the column is recycled to the synthesis reaction step and reused is industrially employed.

In this distillation step, a small amount of allyl alcohol is produced by the reaction of a part of the allyl acetate produced in the synthesis reaction step with water, and depending on the distillation conditions, some allyl alcohol is contained in the acetic acid at the bottom of the column. Since acetic acid containing allyl alcohol is recycled and reused, a small amount of allyl alcohol may be supplied to the allyl acetate synthesis reaction step.

Allyl acetate recovered from the top is hydrolyzed to acetic acid and allyl alcohol.

Then, allyl alcohol is recovered as a product from the top of the column by distillation, and the acetic acid recovered from the bottom of the column is circulated to the synthesis reaction step and reused.

In this distillation step, depending on the distillation conditions, some allyl alcohol is contained in the acetic acid at the bottom of the column.
Allyl alcohol may be supplied as an impurity in the recovered acetic acid to the allyl acetate synthesis reaction step.

According to the present invention, it has been found that the activity of the palladium catalyst is reduced when allyl alcohol is contained in recycled acetic acid, that is, when the raw material gas in the allyl acetate synthesis reaction step contains a certain concentration or more. Made based on

A study on the relationship between the allyl alcohol concentration and the catalytic activity in the total charge gas mixed with allyl alcohol-containing recycle gas showed that the higher the allyl alcohol concentration, the more the catalytic activity decreased, and the higher the allyl alcohol concentration. It has been found that if the content is less than 100 ppm in the total mixed gas of the supplied source gas and the recycle gas, the catalytic activity does not affect the actual water droplets.

The allyl alcohol concentration in acetic acid to be recycled varies depending on the distillation conditions.

In general, if distillation conditions are selected so as to suppress the content of acetic acid in the allyl acetate obtained from the top in the distillation step of separating allyl acetate produced in the production process of allyl acetate and unreacted acetic acid, acetic acid or acetic acid in the bottom liquid is obtained. -Allyl alcohol increases in water.

In the distillation step of separating allyl alcohol and acetic acid generated in the allyl acetate decomposition step, if distillation conditions are selected so as to reduce acetic acid in the allyl alcohol distilled off from the top of the column, allyl alcohol will be contained in the acetic acid in the bottom liquid. Alcohol increases and the content of allyl alcohol in the recycled acetic acid increases.

Conversely, conditions such that acetic acid increases in the allyl acetate at the top in the distillation in the above-mentioned allyl acetate production process, and that acetic acid increases in the allyl alcohol in the top in the distillation in the hydrolysis process of allyl acetate described above. Choosing appropriate distillation conditions can reduce the content of allyl alcohol in the recycled acetic acid, but if the concentration of acetic acid in the allyl acetate is high, the hydrolysis of allyl acetate is an equilibrium reaction, so that the production of allyl alcohol is Disadvantageous.

On the other hand, if the concentration of acetic acid in the allyl alcohol obtained by hydrolysis is high, it is necessary to remove acetic acid in the allyl alcohol by neutralization or the like, which is not preferable because the use rate of acetic acid deteriorates.

The following operation is performed in the distillation step for separating acetic acid and allyl acetate generated in the production process of allyl acetate.

For example, as a charging solution, 22.0 parts by weight of allyl acetate,
Water 20.2 parts by weight, acetic acid 57.1 parts by weight, allyl alcohol 0.7
A case in which a mixture consisting of parts by weight is supplied from the bottom 17 columns of a 50-stage distillation column and operated at a reflux ratio of 2.0 will be described.

The general operating conditions of the distillation column can be summarized as follows.

That is, if the extraction rate is increased, the reflux ratio is increased, or the charging position is lowered, the allyl alcohol concentration decreases. In addition, since this distillation is performed by dropping water at the bottom of the column, raising the temperature near the supply position of the distillation column lowers the allyl alcohol concentration. Pressure).

In the distillation step for separating allyl alcohol and acetic acid, the following operation is performed.

For example, 19.0 parts by weight of water, 38.0 parts of acetic acid
Parts by weight, a mixture consisting of 43.0 parts by weight of allyl alcohol
A case in which the mixture is supplied to the 25th stage from the bottom of a 40-stage distillation column and operated at a reflux ratio of 2.0 will be described. Set the temperature of the 10th stage from the bottom to 10
By operating so as to fall within the range of 4 to 108 ° C., the allyl alcohol concentration in the bottom liquid can be kept at 100 ppm or less. Expressed in general operating conditions of the distillation column, it is as follows. That is, if the reflux ratio is increased or the charging position is increased, the allyl alcohol concentration decreases. Since this distillation is performed such that almost no water falls to the bottom of the column, the temperature near the charging position is 104 to 108 ° C.
Outside the range of (normal pressure), the allyl alcohol concentration increases.

As the catalyst used in the method for producing allyl acetate of the present invention, a general palladium catalyst for producing allyl acetate from propylene, oxygen and acetic acid is used.

It is more preferable to use a palladium catalyst to which an alkali metal acetate is added.

The shape of the catalyst used in the method of the present invention is not particularly limited, and may be spherical, tablet, pellet, or the like.

The production of allyl acetate according to the present invention is carried out by charging the catalyst into a suitable reactor at a temperature of 100 to 300 ° C., preferably 120 to 200 ° C., and a reaction pressure of normal pressure to 30 atm, preferably normal pressure to 10 atm. The reaction is performed under pressure. Since the supplied acetic acid is theoretically entirely recycled, it is not necessary to newly supply the acetic acid, but only the amount corresponding to the amount lost during the process is newly added to obtain a desired reaction charge composition.

Although the composition of the source gas can be varied widely, it is preferable to perform the operation outside the explosion range.

Further, an inert gas such as nitrogen may be used as a diluting gas, and a saturated hydrocarbon such as propane may be present.

According to the production method of the present invention, a high space-time yield can be maintained over a long period of time by suppressing the allyl alcohol concentration in the charged gas mixed with the recycled gas to a certain value or less, so that allyl acetate is industrially advantageous. It is possible to manufacture.

Hereinafter, the effects of the present invention will be described in detail with reference to Examples and Comparative Examples.

(Example 1) Palladium and potassium acetate were converted to silica (pore volume 0.78 ml).
/ g, average pore radius of 150A, bulk density of 540g /), packed in a reactor with a catalyst having a particle size of 5mm, charged with 12% propylene, 7.5% oxygen, 9.0% acetic acid The gas was adjusted to 71.5%, supplied onto the catalyst heated to 145 ° C. at a space velocity of 1800 hr−1, and reacted at a reaction pressure of 4.0 kg / cm ² (gauge pressure).

The raw acetic acid used was a mixture of the unreacted acetic acid recovered in the allyl acetate production step by distillation and the acetic acid obtained in the allyl acetate hydrolysis step recovered by distillation.

The following conditions were selected to keep the allyl alcohol concentration at 100 ppm or less.

As a charged liquid, a mixture composed of 19.0 parts by weight of water, 38.0 parts by weight of acetic acid, and 43.3 parts by weight of allyl alcohol was supplied to the 25th stage from the bottom of a 40-stage distillation column and operated at a reflux ratio of 2.0. By operating the temperature of the 10th stage from the bottom to be in the range of 104 to 108 ° C, the allyl alcohol concentration in the bottom liquid is 100p
pm or less.

This liquid was then recycled to the reactor inlet and mixed with freshly supplied raw materials.

As a result, the allyl alcohol concentration in the raw material gas at the reactor inlet was 40 ppm, and a space-time yield of allyl acetate per catalyst of 166 kg / hour (3.98 T / m ³ · day) was obtained.

(Comparative Example 1) The same reaction as in Example 1 was performed except that the amount of allyl alcohol in the acetic acid obtained in the hydrolysis step of allyl acetate was increased to adjust the allyl alcohol concentration at the reactor inlet to 300 ppm.

As a result, the space-time yield of allyl acetate per catalyst is
It was reduced to 149kg / time (3.58T / m ³ · day).

(Examples 2, 3 and Comparative Examples 2, 3, 4) In order to clarify the effect of allyl alcohol on the activity, allyl alcohol was added to the charged gas and reacted under the same reaction conditions as in Example 1. , Table 1 were obtained.

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Claims (1)

(57) [Claims] 1. A process for producing allyl acetate by reacting propylene, oxygen and acetic acid in the gas phase in the presence of a palladium catalyst, and then hydrolyzing the allyl acetate. In addition, when the mixture containing a small amount of allyl alcohol is circulated through the reaction raw material gas and supplied to the reaction, the stage of charging the distillation column for separating acetic acid and allyl alcohol, the reflux ratio, and the temperature in the distillation column are adjusted. A method for producing allyl acetate and allyl alcohol, wherein the concentration of allyl alcohol in the reaction raw material gas is reduced to 100 ppm or less.