JPH10139728A - Production of methacrylic acid-derived product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing cyclohexyl methacrylate by reactional operation involving no formation of any polymerized product followed by purification through distillation. SOLUTION: In producing the aimed cyclohexyl methacrylate through such processes that methacrylamide sulfate prepared from acetonecyanhydrin or methacrylonitrile and sulfuric acid is hydrolyzed to form methacrylic acid which, in turn, is reacted with cyclohexanol, cyclohexanol is added to an aqueous ammonium bisulfate solution containing sulfuric acid resulted from recovering the methacrylic acid as a mixture with water after the hydrolysis, and a treatment is conducted under heating followed by separating the cyclohexanol which is then reacted with the methacrylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing cyclohexyl methacrylate from methacrylic acid and cyclohexanol.

[0002]

2. Description of the Related Art In order to produce cyclohexyl methacrylate from methacrylic acid and cyclohexanol, the reaction is a reaction between methacrylic acid, which is extremely easily polymerized, and cyclohexanol containing or generating peroxide. Is needed.

As a contrivance, for example, a method in which an organic sulfonic acid is added to a cyclic alcohol, followed by heat treatment, and then an unsaturated carboxylic acid is added to carry out an esterification reaction (Japanese Patent Publication No. Hei.
JP-A-16821), a method of subjecting a cyclic alcohol to heat treatment in the coexistence of water and an organic carboxylic acid, and then adding an unsaturated carboxylic acid to carry out an esterification reaction (Japanese Patent Application Laid-Open No. Sho 6-1994).
3-99037) and the like. However, these methods have the following problems, and improvements have been demanded.

(1) A method in which an organic sulfonic acid is added to a cyclic alcohol, heat-treated, and then an unsaturated carboxylic acid is added to carry out an esterification reaction is a normal batch reaction. There is no countermeasure against the adverse effects of polymerization when the reaction is repeatedly performed, and the method cannot be applied to the case of performing a continuous reaction which is essential for effective production on an industrial scale.

(2) A method of subjecting a cyclic alcohol to heat treatment in the coexistence of water and an organic carboxylic acid and then adding an unsaturated carboxylic acid to carry out an esterification reaction is basically similar to the above (1). The only difference is the coexistence of water.However, since the raw material cyclohexanol is usually added with water to prevent its coagulation, ordinary industrial products are usually converted to normal reaction procedures. It is not a method for effectively preventing the esterification reaction during long-term operation or the generation of a polymer in the product distillation step.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a method for producing cyclohexyl methacrylate from methacrylic acid and cyclohexanol.
An object of the present invention is to provide a method for producing cyclohexyl methacrylate which can prevent generation of a polymer in a synthesis reaction and a distillation purification step.

[0007]

Accordingly, the present inventors have conducted intensive studies on the prevention of polymerization when hydrolyzing methacrylamide sulfate to obtain methacrylic acid and then reacting with cyclohexanol to produce cyclohexyl methacrylate. As a result of the stacking, cyclohexanol is stabilized by heat treatment of cyclohexanol with an aqueous solution of ammonium bisulfate containing sulfuric acid after methacrylic acid is recovered together with water by hydrolysis, and the esterification reaction with methacrylic acid, and further the next step The present inventors have found that a long-time continuous production is possible without generating any polymer in the distillation step, and the present invention has been completed.

That is, according to the present invention, methacrylamide sulfate obtained from acetone cyanohydrin or methacrylonitrile and sulfuric acid is hydrolyzed to obtain methacrylic acid, and the methacrylic acid is reacted with cyclohexanol to obtain cyclohexyl methacrylate. In the method of producing, after the methacrylic acid after hydrolysis is recovered as a mixture of water, to an aqueous solution of ammonium bisulfate containing sulfuric acid, cyclohexanol is added and heat-treated, and then the cyclohexanol is separated, and then the separated cyclohexanol is separated. A process for producing cyclohexyl methacrylate, characterized by reacting cyclohexanol with methacrylic acid.

Cyclohexanol is generally liable to generate peroxide when coexisting with oxygen in the air, and when used directly in an esterification reaction with an unsaturated carboxylic acid, methacrylic acid and an ester formed by the peroxide are generated. Polymerization easily occurs. Therefore, as described above, various devices have been conventionally devised.

The present invention solves the above problem by first hydrolyzing methacrylamide sulfate to form methacrylic acid with water, and then by steam distillation or heating or by simple two-phase separation to obtain ammonium bisulfate containing sulfuric acid. A method of separating methacrylic acid by a method such as distillation after separation from an aqueous solution was employed.

Next, the cyclohexanol may be a pure product or a product containing water for preventing coagulation, but the cyclohexanol is added to an aqueous solution of ammonium bisulfate containing sulfuric acid after the separation of methacrylic acid, followed by heat treatment. I do. At this time, the aqueous ammonium bisulfate solution is preferably kept in a heated state in order to separate methacrylic acid. However, if it has already been cooled, it is heated again and kept at 80 to 140 ° C., and cyclohexanol is added for 10 minutes. Process for up to 30 minutes.

The heating method is usually performed in two ways. One is a method of performing only heat treatment without distillation using a kettle, and the other is a method of performing heat distillation together with an aqueous solution of ammonium bisulfate. Either method produces an effect.

As mentioned above, cyclohexanol is known to generate peroxide in the presence of air and to be decomposed by dehydration with sulfuric acid. In the present invention, however, surprisingly, methacrylic acid after separation of methacrylic acid is surprising. The use of ammonium bisulfate solution containing sulfuric acid reduces the peroxide by the action of sulfuric acid in the ammonium bisulfate solution without causing the generation of polymers that are thought to be due to peroxide and the dehydration of alcohol by sulfuric acid. This enabled the esterification reaction and distillation.

The alcohol after the heat treatment is sent to a separation step. Separation method in the case of heat treatment without distillation using a kettle, in order to enhance the effect of utilizing the limit of mutual solubility, to cool the treatment liquid and solidify the ammonium bisulfate aqueous solution containing sulfuric acid or withdraw as an aqueous layer, The alcohol is taken out of the oil layer with water saturated. Subsequently, the alcohol containing water can be used for the reaction as it is. However, in order to obtain an alcohol having a lower water content, distillation is performed. Water is withdrawn at the top of the column by distillation as an azeotrope with the alcohol, where it is separated into an aqueous layer and an alcohol layer due to differences in mutual solubility. Water-free alcohol is obtained from the bottom.

On the other hand, when heat distillation is performed, water and alcohol form an azeotropic mixture, but the mutual solubility is limited. Therefore, the condensate is separated into two layers, and the alcohol is taken out from the oil layer. The aqueous layer is sent to a recovery process. The cyclohexanol thus obtained is used for an esterification reaction with methacrylic acid using a usual catalyst, for example, paratoluenesulfonic acid, sulfuric acid, an acidic ion exchange resin and the like.

At the time of the reaction, first, cyclohexanol prepared as described above, which is not easily polymerized by itself, is charged into a reaction vessel together with a catalyst and a polymerization inhibitor, and then methacrylic acid purified by the above method is charged. The reaction generates water, and may be heated under reduced pressure to remove by distillation, or may proceed by distillation while forming an azeotrope with water and adding substances inert to the reaction.

The method of charging the raw materials does not need to be particularly limited. That is, it is possible to use a method in which methacrylic acid is charged first and then an alcohol is added, or a method in which both are continuously added and the product is continuously extracted while continuously dehydrating. Regardless of the method selected, the problem of polymerization with cyclohexanol, methacrylic acid or the resulting ester does not occur if the method of the present invention is carried out.

[0018]

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

[0019]

【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.
The methacrylamide sulfate obtained by mixing with 0 kg was charged into a reaction vessel equipped with an external heating device and a steam distillation device. Next, 54 kg of water was added, and after the reaction was performed for 3 hours while maintaining the liquid temperature at 120 ° C., heating was performed while blowing steam,
Methacrylic acid was removed with water. Further, 100 kg of cyclohexanol was added to the remaining liquid in the reaction vessel,
For 20 minutes. Thereafter, the entire amount of the liquid in the kettle was withdrawn and cooled, and cyclohexanol was taken out from the upper layer. Most of the lower aqueous solution of ammonium bisulfate solidified.

In 100 kg of cyclohexanol, 0.5 kg of phenothiazine and 10 gr of paratoluenesulfonic acid
While maintaining the temperature at 120 ° C.
86 kg of methacrylic acid was added and reacted. After distilling off the by-produced water, neutralize with caustic soda, take out the upper layer separated into two layers, and send it to a distillation column having 10 stages,
The methacrylic acid and cyclohexanol were first removed from the top to give the product cyclohexyl methacrylate.
After repeating these operations 7 times, the reaction vessel and the periphery of the distillation column were inspected. As a result, no problematic polymer was found.

Example 2 100 kg of cyclohexanol was added to 200 kg of an aqueous solution of ammonium bisulfate containing sulfuric acid after collecting the methacrylic acid obtained in the same manner as in Example 1, followed by heating and distillation. The distillate was a mixture of water and cyclohexanol and the condensate separated into two layers. The upper layer was 90% cyclohexanol and the rest was water. The cyclohexanol and methacrylic acid thus obtained were reacted with methacrylic acid in the same manner as in Example 1, and the reaction was continued while removing excess water and water generated by the reaction from the reaction system as an azeotropic mixture with cyclohexanol. . Cyclohexanol shortaged by distillation was newly added to the reaction system. After completion of the reaction, the catalyst was neutralized with an alkali and separated into two layers to obtain 164 kg of cyclohexyl methacrylate from the upper layer.

This is firstly fed into the middle part of a distillation column having 20 plates, and low-boiling impurities such as methacrylic acid and cyclohexanol are removed from the top, and cyclohexyl methacrylate is taken out from the bottom. 2
It was fed into the middle of a distillation column with zero stages and pure cyclohexyl methacrylate was obtained from the top. In a series of distillation operations, a polymerization inhibitor was added from the charged liquid and the top of the column according to a standard method, and distillation was carried out while introducing a small amount of air from the bottom. After such an operation, the reaction kettle and the distillation column were inspected, and as a result, no problematic polymer was found.

COMPARATIVE EXAMPLE 1 A methacrylic acid obtained in the same manner as in Example 1 was reacted with the same polymerization inhibitor and catalyst as in Example 1 without treating the purchased cyclohexanol. The liquid was viscous. The reaction-terminated liquid was charged into the same distillation column as in Example 1 and subjected to distillation. As the distillation proceeded, the viscosity of the bottom liquid pool increased, and when half of the liquid was recovered, solidification occurred and the distillation was interrupted. When the inside of the distillation column was inspected, adhesion of a polymer was observed in a portion where gas accumulation occurred.

[0024]

According to the present invention, it is possible to stabilize cyclohexanol, which causes the generation of a polymer, by heat-treating the remaining ammonium bisulfate solution containing sulfuric acid obtained by hydrolysis of methacrylic acid. In addition, there is an effect that generation of a polymer in a synthesis reaction of cyclohexyl methacrylate and purification by distillation can be prevented.

[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 Heat treatment tank 3 Separator 4 Cyclohexyl methacrylate synthesis reaction tank 5 Low boiling removal distillation column 6 Product purification tower 7 Methacrylamide sulfate inlet 8 Water inlet 9 Generated methacrylic acid outlet 10 Cyclohexanol inlet 11 Contains sulfuric acid Bisulfuric acid solution outlet 12 Reaction catalyst inlet 13 Methacrylic acid inlet 14 Low boiling impurity outlet 15 Product outlet 16 High boiling impurity outlet

Claims (4)

[Claims] 1. A method for producing cyclohexyl methacrylate by hydrolyzing methacrylamide sulfate obtained from acetone cyanohydrin or methacrylonitrile and sulfuric acid to obtain methacrylic acid, and then reacting the methacrylic acid with cyclohexanol. In the method, cyclohexanol is added to an aqueous ammonium bisulfate solution containing sulfuric acid after the methacrylic acid after hydrolysis is recovered as a mixture of water, and heat treatment is performed, and then the cyclohexanol is separated, and then the separated cyclohexanol is separated. Is reacted with methacrylic acid to produce cyclohexyl methacrylate. 2. The method for producing cyclohexyl methacrylate according to claim 1, wherein the heating / separating treatment is a distillation operation. 3. The process for producing cyclohexyl methacrylate according to claim 1, wherein the heat treatment does not involve a distillation operation, and the separation is a two-layer separation method utilizing the limit of mutual solubility. 4. The method according to claim 1, wherein the alcohol layer obtained by separating the two layers is distilled, and the distillate component is further reacted with methacrylic acid using cyclohexanol obtained by separating the two layers. 3. The method for producing cyclohexyl methacrylate according to 3.