JPH10139720A - Production of methacrylic acid and its derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce methacrylic acid and its derivative by carrying out hydrolysis of methacrylamide sulfate in the presence of cyclohexanol. SOLUTION: This production of methacrylic acid and its derivative comprises producing methacrylamide sulfate from acetone cyanhydrin or methacryonitrile and sulfuric acid, adding cyclohexanol to the methacrylamide sulfate, hydrolyzing the methacrylamide sulfate to form methacrylic acid in the condition that the concentration of cyclohexanol in the gas phase inside the hydrolyzing vessel is 0.1-2 times the concentration of methacrylic acid vapor, and taking out the formed methacrylic acid by distillation or cooling of the resultant solution. A methacrylate is obtained by an esterfication reaction of the cyclohexanol- containing methacrylic acid. This reaction system enables prevention of blocking of the equipment, improvement of recovery rate, and decrease of formation of polymerized matter in the synthetic process of derivatives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing methacrylic acid by hydrolyzing methacrylamide sulfate and a method for producing a derivative thereof using the obtained methacrylic acid.

[0002]

2. Description of the Related Art There is a method for producing methacrylic acid from acetone cyanohydrin or methacrylonitrile and sulfuric acid, and then hydrolyzing this to form methacrylic acid and then removing it. In producing a related derivative using the obtained methacrylic acid as a raw material, methacrylic acid is very easily polymerized, and various devices for producing and removing the methacrylic acid without polymerizing have been conventionally proposed. Have been.

[0003] For example, a method in which a hydrolysis reaction tank and a stripper are arranged in series, and a reaction and a recovery are carried out while flowing a flow of a raw material and a flow of steam in countercurrent (Japanese Patent Laid-Open No. 1-311).
No. 042) has been proposed. However, in this method, the generated methacrylic acid is handled in multiple stages at a high temperature, so the generation of a polymer in the reaction tank is unavoidable, which is not suitable for continuous operation. I have.

In the esterification reaction between an unsaturated carboxylic acid and a cyclic alcohol, an organic sulfonic acid is added to the cyclic alcohol, followed by heat treatment, and then an unsaturated carboxylic acid ester which undergoes an esterification reaction by adding an unsaturated carboxylic acid. A manufacturing method (Japanese Patent Publication No. 1-16821) has been proposed. However, this method does not improve the production and removal of methacrylic acid as the other raw material, and a sufficient effect cannot be obtained only by the pretreatment for stabilizing the cyclic alcohol.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for producing methacrylic acid from methacrylamide sulphate, extracting the methacrylic acid and producing a derivative thereof. It is an object of the present invention to improve the recovery rate and further suppress the generation of a polymer during synthesis of a derivative.

[0006]

That is, the present invention provides a method for producing and recovering methacrylic acid by obtaining methacrylamide sulfate from acetone cyanohydrin or methacrylonitrile and sulfuric acid, and then adding water to carry out hydrolysis.
It is intended to provide a method for producing methacrylic acid, wherein a hydrolysis reaction is carried out in the presence of cyclohexanol.

In the present invention, the reaction apparatus used for the hydrolysis reaction of methacrylic acid may be a single reaction tank or a multi-stage reaction tank, and the reaction type may be a batch type or a continuous type. The cyclohexanol used may be a commercial product or a recovered product associated with the practice of the present invention. The water used for the hydrolysis reaction may be fresh water or a product recovered in the practice of the present invention. The combination of these conditions can be arbitrarily selected.

In the present invention, methacrylamide sulfate is obtained from acetone cyanohydrin or methacrylonitrile and sulfuric acid by a conventional method. Then, when methacrylic acid is generated by adding water to the resultant and hydrolyzing it, cyclohexanol is added in advance or simultaneously with the hydrolysis. By adding cyclohexanol, methacrylic acid in the gas layer inside the reaction vessel (boiling point 1 at normal pressure)
(60 ° C.) It is diluted with an azeotropic mixture of cyclohexanol and water having a lower vapor concentration (boiling point at normal pressure: 98 ° C., composition: water: 80% by weight), whereby the generation of a polymer in the gas phase can be prevented.

Further, when the formed methacrylic acid is removed by distillation, the temperature is further increased and the concentration of methacrylic acid in the gas phase is also increased. However, the concentration of methacrylic acid in the vapor is reduced by the azeotropic mixture of cyclohexanol and water. The effect is further remarkable, and generation of a polymer can be prevented. In addition, when methacrylic acid is taken out together with water by taking out the reaction solution instead of distillation and separating it into two layers, cyclohexanol is located in the upper layer together with methacrylic acid to suppress water contamination and concentrate methacrylic acid. Demonstrate. The separation effect utilizing the difference between the mutual solubilities is also exerted when vapor is condensed when methacrylic acid is removed from a reaction solution containing sulfuric acid together with water by distillation.

That is, the condensate containing methacrylic acid, water and cyclohexanol as main components is divided into two layers, a mixture with cyclohexanol containing substantially all of methacrylic acid in the upper layer, and a lower layer in the lower layer. Is divided into two layers, an aqueous layer containing substantially all of the water. The methacrylic acid containing cyclohexanol thus obtained can then be separated from cyclohexanol, or a catalyst can be added in a mixed state without separation to synthesize cyclohexyl methacrylate.

This effect is obtained because the peroxide generated by reacting with oxygen contained in cyclohexanol or in the air is decomposed by heating in advance in an aqueous solution containing sulfuric acid. Therefore, it is presumed that the synthesis of cyclohexyl methacrylate does not cause generation of a polymer.

A small amount of methacrylic acid and cyclohexanol contained in the aqueous layer after the separation of methacrylic acid as a mixture with cyclohexanol is recovered, if necessary, by a method such as distillation or extraction.

When the hydrolysis reaction is carried out continuously in multiple stages, the method of adding cyclohexanol is changed depending on the method of recovering the produced methacrylic acid. For example, in the case of taking out a liquid phase in a multi-stage reaction, it is added to methacrylamide sulfate from the beginning. Alternatively, in the case where distillation is carried out while continuously reacting and taken out from each reaction tank, it is injected into each stage in order to reduce the methacrylic acid concentration in each reaction tank.

The concentration of cyclohexanol in the vapor is adjusted to a concentration that can prevent the condensation of methacrylic acid at a high concentration. The standard of the concentration is 0.1 to 2 times the methacrylic acid vapor. If it is twice or more, the distillation load becomes too large and disadvantageous, and if it is less than 0.1, the amount necessary for synthesizing cyclohexyl methacrylate becomes insufficient. In addition, when excess or deficiency of cyclohexanol occurs, it is adjusted by adding or extracting as appropriate. Usually, a preferable concentration is a concentration close to equimolar to methacrylic acid. In terms of thermal energy, it is more advantageous to take out the liquid phase reaction product as it is than to take it out by distillation.

[0015]

Now, the present invention will be described in further detail with reference to Examples and Comparative Examples.

[0016]

【Example】

Example 1 0.8 kg of phenothiazine as a polymerization inhibitor was added to 85 kg of acetone cyanohydrin, and then 15% of 98% sulfuric acid was added.
100 kg of cyclohexanol was added to methacrylamide sulfate obtained by mixing and reacting 0 kg. Next, the mixture was placed in a glass reactor equipped with an external heating device in an amount of 54 kg of water.
And mixed and reacted at a temperature of 120 ° C. for 3 hours. Thereafter, methacrylic acid was taken out as a mixture of cyclohexanol and water by blowing steam into an external heating device. This mixture was cooled and liquefied and separated into two layers, and 80 kg of methacrylic acid, 97 kg of cyclohexanol, and 11 kg of water were obtained from the upper layer liquid. The lower layer liquid was 5 kg of methacrylic acid, 3 kg of cyclohexanol, and 65 kg of water.

The upper layer liquid was taken out, 10 g of paratoluenesulfonic acid and 0.5 kg of hydroquinone were added and charged into the reactor. While reducing the pressure, heating and reacting at 110 ° C., the water was distilled off while removing water as an azeotrope with cyclohexanol, and the distillate was separated into two layers, and the cyclohexanol from which water had been removed was returned to the reactor. , 6
Reacted for hours. Thereafter, the mixture was neutralized with caustic soda, divided into two layers, a polymerization inhibitor was added to the upper layer liquid, and cyclohexyl methacrylate was obtained while injecting a small amount of air from the bottom in a packed column distillation column. After completion of this series of operations, observation of the glass hydrolysis reactor, cyclohexyl methacrylate synthesis reactor, and distillation column revealed that no polymer was generated in any of them.

Example 2 In the same manner as in Example 1, 100 kg of cyclohexanol and 54 kg of water were added to 235 kg of methacrylamide sulfate to carry out a hydrolysis reaction at 120 ° C. for 3 hours, and then cooled without distillation to form two layers. 200 kg of a mixture of methacrylic acid, cyclohexanol and water from the separated upper layer
I got Since the lower layer was solidified, it was dissolved by heating and sent to a distillation column to recover methacrylic acid and cyclohexanol from the top of the column. The recovered mixture was distilled to obtain cyclohexanol and water from the top of the tower. Methacrylic acid was obtained from the bottom of the column. The methacrylic acid and cyclohexanol thus obtained were used in Example 1
As a result of distillation, no polymer was observed in any of the reactor and the distillation column.

Comparative Example methacrylamide sulfate 235 was prepared in the same manner as in Example 1.
kg, and then charged to a glass reactor equipped with an external heating device with 54 kg of water. Reaction temperature 120 ° C
After reacting for 3 hours, methacrylic acid was obtained as a mixture with water by distillation with an external heating device while blowing steam into the reaction tank. A colorless transparent or slightly brown colored solid was observed. Next, methacrylic acid containing water is purified by a distillation column, and is reacted with cyclohexanol using hydroquinone as a polymerization inhibitor and paratoluenesulfonic acid as a catalyst to synthesize cyclohexyl methacrylate using the same apparatus as in Example 1. did. Then, the reaction product liquid showed viscosity, so that hydroquinone was additionally charged, and the mixture was applied to a packed column distillation column. As a result, the pressure difference in the column soon increased, and the distillation could not be continued. Upon disassembly and inspection, it was found that solids were accumulated in the bottom liquid reservoir, and polymer was entrained and accumulated in the middle part of the distillation column packing.

[0020]

According to the method of the present invention, methacrylic acid, which is easily polymerized, is produced and recovered by hydrolysis, and then, when a derivative thereof, cyclohexyl methacrylate is synthesized, the generation of polymer in a reaction tank or a distillation column is considered. There is an effect that continuous stable operation is possible.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a manufacturing process of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydrolysis reaction tank 2 Condenser A 3 Separator A 4 Reactor 5 Condenser B 6 Separator B 7 Separator C 8 Distillation tower 9 Recovery tower 10 Cyclohexanol inlet 11 Methacrylamide sulfate inlet 12 Water inlet 13 Steam inlet 14 water layer outlet 15 catalyst and polymerization inhibitor inlet 16 circulating cyclohexanol 17 reaction water outlet 18 caustic soda inlet 19 water layer outlet 20 low boiling point outlet 21 cyclohexyl methacrylate outlet 22 high boiling point outlet 23 water outlet 24 recovered methacrylic acid and cyclohexanol Exit

Claims (5)

[Claims] 1. A methacrylamide sulfate is obtained from acetone cyanohydrin or methacrylonitrile and sulfuric acid, and then water is added to produce methacrylic acid by hydrolysis.
A method for producing methacrylic acid, comprising performing a hydrolysis reaction in the presence of cyclohexanol for recovery. 2. The method for producing methacrylic acid according to claim 1, wherein the concentration of cyclohexanol in the gas phase of the hydrolysis tank is 0.1 to 2 times the concentration of methacrylic acid vapor. 3. The method for producing methacrylic acid according to claim 1, wherein the method for removing the produced methacrylic acid is a method for distilling the reaction solution. 4. The method for producing methacrylic acid according to claim 1, wherein the method for removing the produced methacrylic acid is a method for cooling and separating the reaction solution. 5. A method for producing a methacrylic acid derivative, wherein an esterification reaction is performed with cyclohexanol using the methacrylic acid containing cyclohexanol obtained in any one of claims 1 to 4.