JP2629266B2 - Method for producing methyl methacrylate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel method for producing methyl methacrylate using acetone and methyl formate as raw materials.

Methyl methacrylate is used in large amounts as various polymer raw materials, and is an industrially important intermediate raw material.

(Prior art) As an industrial production method of methyl methacrylate, acetone cyanohydrin (hereinafter referred to as AC
H)), isobutylene and t-
The so-called C4 oxidation method using butanol as a raw material has been put to practical use.

Many other methods have been proposed, such as an oxidative dehydrogenation method of isobutyric acid, a condensation dehydration method of propionic acid or propionaldehyde with formaldehyde, and an ammoxidation method of isobutylene, but they have not been put to practical use yet.

The ACH method is a method of synthesizing ACH from hydrocyanic acid and acetone and reacting ACH with methanol in the presence of excess concentrated sulfuric acid to obtain methyl methacrylate.

This ACH method is easy to react and has a high yield, and is widely practiced at present. However, this method has a disadvantage that a large amount of waste sulfuric acid and ammonium sulfate are produced as by-products, which puts down the production cost of methyl methacrylate.

On the other hand, in the case of the C4 oxidation method, there are inconveniences that many side reactions occur, the yield of methyl methacrylate is low, purification costs are high, and complicated and expensive production equipment is required. Furthermore, there is a drawback that there are restrictions on the procurement of isobutylene and t-butanol as raw materials.

(Means for Solving the Problems) The inventors of the present invention have studied the novel and inexpensive method for producing methyl methacrylate in addition to the fact that the procurement of raw materials is stable and easy. And could be completed.

The present invention is a step of producing ACH by the reaction of hydrocyanic acid and acetone, a step of hydrating ACH obtained in the above step to produce α-hydroxyisobutyric acid amide, and α-hydroxyisobutyric acid amide obtained in the above step. A step of producing methyl α-hydroxyisobutyrate and formamide by reaction with methyl formate using methanol as a reaction solvent, a step of producing methyl methacrylate by dehydrating the separated α-hydroxyisobutyrate obtained in the above step, and The present invention relates to a novel method for producing methyl methacrylate, comprising a step of dehydrating formamide obtained in the methyl formate reaction step to produce hydrocyanic acid and recycling it.

The method of the present invention finally uses acetone and methyl formate as raw materials.
This is a process for producing methyl methacrylate, which does not involve any by-product of ammonium sulfate as in the method.

Acetone is produced in large quantities at low cost and can be easily produced from propylene if necessary.

On the other hand, methyl formate can be easily produced by a carbonylation method or a dehydrogenation method using methanol, which is produced in large quantities at low cost.

In the present invention, the production of ACH by the reaction of hydrocyanic acid and acetone is carried out by a generally known method, and is carried out by mixing both in the presence of a catalyst such as an alkali metal salt or an amine. The reaction proceeds quantitatively and ACH is obtained in high yield.

In the present invention, the production of α-hydroxyisobutyric amide is carried out by reacting a mixture of ACH and water in the presence of a catalyst. As the catalyst, a catalyst that is effective for the hydration reaction of nitriles can be used, and a strong acid such as sulfuric acid is used, but from the economical point of view including treatment, use of a metal catalyst or a metal oxide catalyst is preferable. . Specifically, manganese, copper, nickel or oxides thereof are effective, and manganese oxide is particularly preferable.

The charge ratio of ACH to water is suitably in the range of 10:90 to 90:10. In addition, a solvent such as acetone or methanol can coexist in this system.

When using manganese oxide as a catalyst, the reaction temperature is 20 to 15
0 ° C. is a preferred range, with 40 to 120 ° C. being suitable. The reaction time is preferably from 0.3 to 6 hours, and particularly preferably from 0.5 to 3 hours. The reaction can be carried out in any of a batch system and a flow system.

In the present invention, the production of α-hydroxyisobutyric acid amide and formamide by the reaction of α-hydroxyisobutyric acid amide and methyl formate is also possible by a method of heating a mixture of α-hydroxyisobutyric acid amide and methyl formate in the absence of a catalyst. However, it is effective to carry out in the presence of a solvent and a catalyst.

This reaction is an equilibrium reaction, and the yield of α-hydroxyisobutyrate depends on the molar ratio of α-hydroxyisobutyric acid amide to methyl formate, and the charge ratio of the latter to the former is preferably from 1 to 10, particularly preferably 2 to 6 are preferred.

The addition of the solvent has the effects of increasing the solubility of solid α-hydroxyisobutyric acid amide and increasing the selectivity of the reaction. Methanol is most preferred as the solvent used, and the molar ratio of the solvent to α-hydroxyisobutyric acid amide is preferably 2 to 10.

In the case of a reaction without a catalyst, the reaction temperature is suitably from 180 to 250 ° C., and the reaction time is suitably from 0.5 to 5 hours.

As a catalyst for this reaction, as disclosed in JP-A-58-55444 and JP-A-60-78937, a main catalyst such as a metal salt of an organic acid or an inorganic acid or a metal chelate compound and an organic compound containing nitrogen or phosphorus are used. Examples thereof include those in which a compound accelerator is used in combination, and those in which amidine, a tertiary amine, and a metal carbonyl are further combined.

In the case of these known catalysts, both the reaction rate and the selectivity are insufficient, and the present inventors have continued research and development of high performance catalysts. As a result, they found that alkali metal alcoholates and inorganic solid acids were extremely excellent as catalysts and filed separate applications (Japanese Patent Application Laid-Open Nos. 1-290650 and 1-290651).
issue).

The alkali metal alcoholate as a catalyst in the present invention is synthesized from lithium, sodium, and potassium metals and a lower alcohol, and specific examples include sodium and potassium methylates, ethylates, and butyrates.

As the reaction conditions when the alkali metal alcoholate is used as a catalyst, the amount of the catalyst used is preferably 0.001 to 0.30 mol per 1 mol of α-hydroxyisobutyric acid amide at a reaction temperature of 20 to 100 ° C. and a reaction time of 0.5 to 6 hours.

JP-A-52-3015 discloses an example in which a carboxylic acid ester is produced by reacting a carboxylic acid amide with an alcohol using an alkali metal alcoholate catalyst. In the case of this methanolysis, the reaction temperature is as high as 200 ° C, and a high-pressure reactor is required.Moreover, since ammonia is generated in the reaction, there is a problem in the process such as intermittent pressure release of ammonia. In addition, there is a disadvantage that the yield of the carboxylic acid ester is low.

However, when the esterification reaction using methyl formate is applied in the method of the present invention, all the problems of the reference can be solved.

In the process of the present invention for producing methyl α-hydroxyisobutyrate and formamide from α-hydroxyisobutyric acid amide and methyl formate, when an inorganic solid acid is used as a catalyst, silica, silica-alumina, zeolite and solid phosphorus are used. An acid or the like is effective, and the reaction conditions are suitably a reaction temperature of 170 to 250 ° C. and a reaction time of 0.1 to 5 hours.

The reaction product in this step is separated and recovered by an operation such as distillation, and the target product methyl α-hydroxyisobutyrate is sent to the next step, and the unreacted product is sent to the raw material system.

The production of methyl methacrylate by the dehydration reaction of methyl α-hydroxyisobutyrate can be carried out by a liquid phase reaction using sulfuric acid, phosphoric acid or the like, but is more advantageous by a gas phase reaction using a solid catalyst. Can be implemented.

That is, in the case of the gas phase contact reaction, a solid acid catalyst such as silica, silica-alumina, zeolite, and solid phosphoric acid is used as a catalyst.
It is preferably carried out at ~ 500 ° C. In this case, steam or an inert gas can coexist in the reaction system in order to suppress carbon deposition on the catalyst.

On the other hand, with regard to formamide by-produced simultaneously with the target product methyl α-hydroxyisobutyrate, a hydrocyanic acid is produced by applying a dehydration reaction.

Production of hydrocyanic acid from formamide is carried out in the presence of a solid catalyst such as alumina, silica-alumina and iron-silica by a gas-phase contact reaction, and the reaction temperature is suitably 200 to 600 ° C.
The reaction proceeds quantitatively, producing hydrocyanic acid and water.

The generated hydrocyanic acid is separated and recovered, sent to the ACH production process and recycled.

(Effects of the Invention) According to the present invention, each step proceeds with extremely high selectivity, and methyl methacrylate can be produced in high yield from acetone and methyl formate as raw materials. There are no such undesirable by-products, and it has an extremely high industrial reputation.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited in scope by these Examples.

Example 1 Process (Synthesis of ACH from hydrocyanic acid and acetone) 500 m in internal volume equipped with a stirrer, thermometer, and hydrocyanic acid dropping funnel
116 g of acetone and 1 ml of a 1N aqueous sodium hydroxide solution were charged into a 1 l flask, and 59.4 g of hydrocyanic acid was added dropwise while maintaining the temperature in the flask at 20 ° C.

After the completion of the dropwise addition of cyanuric acid, the reaction was completed at 20 ° C for 2 hours.
Next, the pH of the resulting solution was adjusted to 3 by adding 50% sulfuric acid.

The flask was connected to a reduced pressure system, and unreacted hydrocyanic acid was distilled out of the system to obtain 171 g of ACH.

The purity of ACH was 98.4%, and the ACH yield based on acetone was 99%.

Step (Synthesis of α-hydroxyisobutyric acid amide by hydration of ACH) 63.2 g of potassium permanganate and 500 g of water were heated and stirred at 70 ° C. in a 1-volume flask equipped with a stirrer, a reflux condenser, and a thermometer. .

240 g of an aqueous solution in which 96.2 g of manganese sulfate was dissolved, and 1
40 g of 5% sulfuric acid was added and reacted at 70 ° C. for 3 hours.

After cooling the contents, the precipitate was filtered off with suction and washed with 2.4 l of water. The precipitate cake was dried at 60 ° C. overnight to obtain 74 g of active manganese dioxide, which was used as a catalyst described below.

In a flask having an internal volume of 1 equipped with a stirrer, a reflux condenser, and a thermometer, 150 g of acetone cyanohydrin obtained in the step, 350 g of water, 100 g of acetone, and 60 g of manganese dioxide were successively placed.
And reacted by heating and stirring at 60 ° C. for 5 hours.

The resulting solution was cooled on ice and filtered by suction to separate the catalyst.
As a result of gas chromatography analysis of the filtrate, the reaction rate of ACH was 99.5.
%, The yield of α-hydroxyisobutyric amide was 95% and contained small amounts of acetone and formamide.

The filtrate was distilled under reduced pressure, and the purity as a main fraction was 99.5.
% Of α-hydroxyisobutyric amide was obtained.

Step (Synthesis of α-hydroxyisobutyrate and formamide from α-hydroxyisobutyric acid amide and methyl formate) α-Hydroxyisobutyric acid amide obtained in the step in a stainless steel autoclave having an internal volume of 1 with a stirrer.
6 g, 180 g of methyl formate, 96 g of methanol, and 0.8 g of sodium methylate were charged and reacted by heating and stirring at 60 ° C. for 2 hours.

After cooling the product, gas chromatographic analysis showed that the conversion of α-hydroxyisobutyric acid amide was 62%, the selectivity of α-hydroxyisobutyric acid amide relative to α-hydroxyisobutyric acid amide was 96%, and formamide Has a selectivity of 92
%Met.

After neutralizing sodium methylate in the product solution with hydrochloric acid, it is distilled by a conventional method to recover methyl formate, methanol and α-hydroxyisobutyric amide, and to obtain α of 99% purity.
-59 g of methyl hydroxyisobutyrate and 20 g of formamide with a purity of 99% were obtained. The recovery including the middle distillate was quantitative.

Step (Synthesis of methyl methacrylate by dehydration of methyl α-hydroxyisobutyrate) To a mixture of 20 g of sodium dihydrogen phosphate and 80 g of water, add 60 g of Fujidivisone silica gel (16 to 24 mesh), and distill water under reduced pressure. The catalyst was prepared by drying at 150 ° C. overnight and used in the following reaction.

Quartz reactor equipped with evaporator and reflux condenser (inner diameter
14Φ × 40L) was charged with 10 g of the catalyst and heated in an electric furnace, and the maximum temperature of the catalyst layer was controlled at 400 ° C.

A mixture having a molar ratio of methyl α-hydroxyisobutyrate obtained in the step to methanol of 2 to 1 was converted to 10
g was supplied continuously, and the reaction was performed for a total of 10 hours.

As a result of analyzing the reaction product, the conversion of methyl α-hydroxyisobutyrate was 99%, and the yield of methyl methacrylate was 88% based on the charged methyl α-hydroxyisobutyrate.
And methacrylic acid, which is another active ingredient, is obtained at a yield of 6.
It was produced at 8%.

Step (Production of hydrocyanic acid by dehydration of formamide) A reactor similar to that described in the step was charged with 5 g of alumina catalyst (N612) manufactured by JGC Chemicals, and the maximum temperature of the catalyst layer was 500
C. was controlled.

Along with a small amount of diluent nitrogen gas, the formamide obtained in the process was continuously supplied at a rate of 4.5 g / hour, and the reaction was continued for 10 hours. The non-condensable gas was passed through a flush bottle containing water to absorb the entrained hydrocyanic acid.

As a result of analyzing the reaction condensate and absorption solution, the conversion of formamide was 98%, and the hydrocyanic acid yield based on formamide was
It was 92%.

If this product is distilled by a conventional method, high-purity hydrocyanic acid is obtained and is recycled as a raw material for producing ACH.

Example 2 After performing the steps and steps exactly as in Example 1, the steps were performed as follows.

41.4 g of α-hydroxyisobutyric acid amide and methyl formate 1 were placed in a 500 ml stainless steel autoclave with a stirrer.
44 g, methanol 76.8 g, and 10 g of a silica-alumina catalyst (N631H) manufactured by JGC Chemicals, which had been calcined at 800 ° C. for 3 hours in advance, were reacted at 200 ° C. for 3 hours.

After cooling on ice, the contents were taken out and the catalyst was separated by suction filtration. As a result of gas chromatographic analysis of the filtrate, the reaction rate of α-hydroxyisobutyric acid amide was 54.5%, the selectivity of α-hydroxyisobutyric acid methyl based on α-hydroxyisobutyric acid was 92.8%, and the selectivity of formamide was 92.8%. 87.5
%Met.

The methyl α-hydroxyisobutyrate and formamide obtained in the step were subjected to the steps of Example 1 and the same operation as in the step. As a result, exactly the same results as in Example 1 were obtained.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-78939 (JP, A) JP-A-60-78937 (JP, A)

Claims (1)

(57) [Claims] 1. A process for producing acetone cyanohydrin from hydrocyanic acid and acetone; a process for hydrating the acetone cyanohydrin obtained in the above process to produce α-hydroxyisobutyric amide; A step of producing methyl α-hydroxyisobutyrate and formamide from hydroxyisobutyric acid amide and methyl formate using methanol as a reaction solvent; dehydrating the methyl α-hydroxyisobutyrate separated from the product obtained in the above step to obtain methyl methacrylate And a step of dehydrating formamide separated from the product obtained in the methyl formate reaction step to produce hydrocyanic acid and circulating and using the same, for producing methyl methacrylate.