JPS6320415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing acrylic esters or methacrylic esters. Specifically, the present invention involves a direct esterification reaction of acrylic acid or methacrylic acid [hereinafter referred to as (meth)acrylic acid] and a lower aliphatic alcohol having 1 to 3 carbon atoms at a low molar ratio in the presence of an acidic catalyst. The present invention relates to a method for continuously producing (meth)acrylic acid ester.

It is well known that the esterification reaction of (meth)acrylic acid with lower aliphatic alcohols such as methanol, ethanol, isopropanol, etc. gives the corresponding esters, and this reaction can be an equilibrium reaction. is (meta)
It is well known that in addition to acrylic esters, unreacted alcohol, (meth)acrylic acid, and reaction product water coexist. In order to separate (meth)acrylic acid ester and produced water from such reaction products, distillation operations have conventionally been utilized. However, it is also true that water has a strong affinity with (meth)acrylic acid, and when the produced water is distilled off, (meth)acrylic acid tends to inevitably be distilled out together with water.
Even if the number of distillation stages and the reflux ratio are increased, this cannot be separated to a satisfactory degree, complicating the subsequent (meth)acrylic acid ester purification process, and producing a large amount of waste water. Furthermore, if the molar ratio of alcohol to (meth)acrylic acid supplied to the esterification reaction is lowered, the amount of (meth)acrylic acid distilled out together with the produced water tends to increase. It is common to carry out the reaction in a high range of 5 to 5, and costs are unavoidable due to recovery of unreacted alcohol, increase in reactor capacity, and increase in utility.

On the other hand, in order to suppress the above-mentioned affinity between water and (meth)acrylic acid, it is also known that an azeotropic agent having a stronger affinity with water is added to allow the reaction product water to be distilled out from the reaction product by azeotropy. It is being Examples of these entrainers include benzene, toluene, and xylene. However, separation of these entrainers and (meth)acrylic esters is not easy, and requires complicated steps including recovery, which is extremely disadvantageous economically.

The present invention overcomes the drawbacks of the prior art and provides a process for continuously producing (meth)acrylic acid ester directly from (meth)acrylic acid and lower aliphatic alcohol. Because the molar ratio of (meth)acrylic acid and lower aliphatic alcohol supplied by the reaction system is in the low range of 1:1 to 2, the alcohol recovery process is greatly simplified and utilities such as steam are also reduced. The object of the present invention is to provide a process that can greatly reduce the amount of alcohol used and still provide extremely high yields of (meth)acrylic acid ester for both (meth)acrylic acid and alcohol compared to conventional methods.

That is, the present invention is specified as follows.

(1) Acrylic acid or methacrylic acid with 1 or more carbon atoms
When producing an acrylic acid ester or a methacrylic acid ester by esterifying the lower aliphatic alcohol of No. 3 in the presence of an acidic catalyst, the molar ratio of the acrylic acid or methacrylic acid to be supplied as a raw material and the alcohol is 1:1.0 to 1.0.
When the esterification reaction is carried out at a temperature of 60 to 100°C and the resulting esterification reaction mixture is distilled, the water concentration in the distillate obtained is 3 to 8 in the case of methyl acrylate. Weight%, methyl methacrylate, ethyl acrylate,
8 to 8 for ethyl methacrylate, isopropyl acrylate or isopropyl methacrylate
Acrylic ester or methacrylic acid that is substantially free of acrylic acid or methacrylic acid is obtained by newly supplying the acrylic ester or methacrylic ester from outside the system to the distillation column so that the concentration is in the range of 13.5% by weight. An acrylic ester characterized in that a distillate consisting of ester, esterification reaction product water and unreacted alcohol is quenched, and the distillation column liquid from which the product water has been substantially removed is recycled to the esterification reaction. Or a method for producing methacrylic acid ester.

The present invention will be explained in more detail below.

Raw materials (meth)acrylic acid and lower aliphatic alcohol are supplied to a reaction tank containing an acidic esterification catalyst and maintained at a constant temperature. Since the esterification reaction is an equilibrium reaction, the reaction product contains unreacted alcohol and (meth)acrylic acid. In the distillation column, the target product (meth)acrylic ester and the produced water must be distilled out, while the bottom liquid contains unreacted (meth)acrylic acid ester.
Acrylic acid remains and will be supplied for the esterification reaction. In order for this distillation to be carried out as desired, it is necessary to newly feed (meth)acrylic acid ester of the same type as the target product from the top of the column, and to avoid containing substantially unreacted (meth)acrylic acid. It has been found that it is advantageous to distill off the acrylic ester, product and traces of unreacted alcohol.

Mainly unreacted (meth)acrylic acid, a small amount of water, and (meth)acrylic acid ester remain on the tank liquid side, and are recycled to the esterification reaction tank.
It is preferable that the circulating amount of the liquid in the tank consisting of substantially unreacted (meth)acrylic acid be at least 1 times the weight of the newly supplied raw material. The reason is that the composition of the mixed raw material supplied to the esterification reaction tank is (meta)
This is because it has been found that by increasing the amount of acrylic acid in excess, the production of impurities, mainly alkoxy compounds, generated in the esterification reaction is greatly reduced. This means that the yields of both (meth)acrylic acid and alcohol are improved.

That is, the present inventors have found that when the molar ratio of alcohol to (meth)acrylic acid as a raw material supplied to an esterification reaction tank is in the range of 0.5 to 1.0, the yield from (meth)acrylic acid has conventionally increased. 91~
94%, and the yield from alcohol was 94-97%, but they found that the former reached an unprecedentedly high level of 96-99% and the latter 97-99.5%. Moreover, along with this operation, the distillate of the distillation column must be obtained so as to substantially match the theoretical value of the mass balance between the newly supplied (meth)acrylic acid and the alcohol.
In combination with an operation in which an amount of (meth)acrylic acid ester corresponding to the amount of substantially 100% conversion of acrylic acid into ester and corresponding produced water is extracted as a distillate, extremely smooth (meth)acrylic acid ester conversion is achieved. ) A continuous production process of acrylic esters is carried out.

The fraction containing (meth)acrylic acid ester and produced water in a substantial amount obtained from the distillation column is separated into two phases, and the aqueous phase undergoes a recovery process for the alcohol and (meth)acrylic acid ester contained therein. be passed around. In addition, (meth)acrylic acid ester is obtained by separating alcohol and water from the oil phase. According to the method of the present invention, due to the low molar ratio reaction as described above, the amount of unreacted alcohol is extremely small, and the process is greatly simplified in that the conventional extraction step for alcohol recovery is no longer necessary. can be measured.

On the other hand, (meth)acrylic acid is substantially retained in the bottom liquid of the distillation column, and the weight is at least 1.0 times that of (meth)acrylic acid and alcohol that are newly supplied to the esterification reaction tank. It is preferable that the water be supplied in a circular manner. Increasing the circulation volume does not have much effect on the reaction, but increasing it is meaningless, and there is no need to exceed 7 times the circulation volume. In particular, when the target is acrylic acid methyl ester, the ratio is preferably 1.0 to 2.0 times, and when the target is methyl methacrylate, ethyl or isopropyl (meth)acrylate, the ratio is preferably 2.0 to 5.0 times. The molar ratio of (meth)acrylic acid and alcohol newly supplied to the esterification reaction tank is in the range of 1:1.0 to 2.0, preferably 1.1 to 1.5.

The acidic catalyst used in the present invention includes liquid catalysts such as para-toluenesulfonic acid, sulfuric acid, sulfonic acid, hydrochloric acid, etc., and solid acid catalysts such as strongly acidic ion exchange resins, and solid acid catalysts are particularly advantageous. It is. The esterification reaction is usually carried out in the presence of a polymerization inhibitor. Polymerization inhibitors generally include hydroquinone, hydroquinone monomethyl ether, phenothiazine, etc., and are used in an amount of 0.0005 to 0.5% by weight based on (meth)acrylic acid. The reaction conditions for the esterification reaction are 60-100℃,
The temperature is preferably 60 to 90°C, and the pressure is sufficient to maintain the reaction rate in a liquid phase, usually normal pressure to slightly increased pressure (0.5 to 2.0 Kg/cm ² G). The residence time of the raw materials in the reaction vessel is at least 0.5 hours, but usually from 0.5 to 20 hours, preferably from 0.5 to 10 hours; longer residence times are not economically advantageous.

Next, a specific example of the method of the present invention will be explained with reference to FIG.

(Meth)acrylic acid is supplied through conduit 1, alcohol is supplied through conduit 2, and the bottom liquid from distillation column 5 containing a large amount of unreacted (meth)acrylic acid is supplied to conduit 6.
The bottom liquid of the distillation column containing unreacted (meth)acrylic acid and the newly supplied (meth)acrylic acid and alcohol are mixed together.
It is supplied to a reaction tank 3 containing an acidic catalyst. If necessary, part or all of the bottom liquid from the distillation column containing unreacted (meth)acrylic acid is introduced into a thin film evaporator, etc. in order to remove high-boiling compounds, polymers, etc. generated during the reaction from the system. However, it is preferable to return the distilled light components to the circulating fluid to prevent heavy components from accumulating in the reaction system.

In reaction tank 3, (meth)acrylic acid and alcohol are esterified to near equilibrium, and the reaction mixture consisting of (meth)acrylic ester, water, unreacted alcohol, and (meth)acrylic acid is passed through conduit 4 to distillation column 5. Supplied. In the distillation column 5, when distilling out (meth)acrylic acid ester in an amount substantially equal to the theoretical value of the material balance between (meth)acrylic acid and alcohol, as well as produced water and unreacted alcohol, water is distilled from the conduit 7. The same type of (meth)acrylic ester is supplied to obtain a distillate substantially free of (meth)acrylic acid. At this time, the amount of (meth)acrylic acid ester supplied from the conduit 7 is determined based on the water concentration in the distillate, 3 to 8% by weight in the case of methyl acrylate, methyl methacrylate, and ethyl (meth)acrylate. In the case of isopropyl ester, it is necessary to supply it in a range of 8 to 13.5% by weight. The (meth)acrylic acid ester supplied from the conduit 7 may be the liquid from the conduit 10 or the conduit 21, but the liquid from the conduit 7 is economically preferable.

An amount of (meth)acrylic ester produced substantially equal to the theoretical mass balance of (meth)acrylic acid and alcohol, as well as an amount of produced water, unreacted alcohol and the amount of (meth)acrylic ester supplied in conduit 7. is sent to an oil-water separation tank 9 via a conduit 8.

The (meth)acrylic acid ester phase separated in the oil/water separation tank 9 is supplied to the light fraction separation column 12 via a conduit 10, but may also be passed through an extraction column depending on the case. In the light fraction separation column 12, the (meth)acrylic acid ester from which alcohol, water and light impurities have been separated is taken out from the bottom of the column via a conduit 17.
A portion is recycled via line 7 to distillation column 5, and the remainder is fed via line 18 to rectification column 19.

In the light fraction separation column 12, distilled (meth)
The acrylic ester, alcohol and water are sent via line 13 to an oil-water separation tank 14 and the (meth)acrylic ester phase is recycled via line 15 to the top of the column. The aqueous phase separated in oil-water separation tanks 9 and 14 is taken out via conduits 11 and 16 and sent to an alcohol recovery tower if necessary, where alcohol and (meth)acrylic acid ester are recovered and supplied to the reaction tank again via conduit 2. be done. The (meth)acrylic acid ester purified in the rectification column 19 is passed through conduits 20 and 2.
1 and then taken out as a product from the bottom of the tower into a conduit 22.
After that, the bottom liquid is taken out.

EXAMPLES The method of the present invention will be explained in more detail with reference to examples below, but the invention is of course not limited to the following examples.

Example 1 In a stainless steel reaction tank filled with strongly acidic cation exchange resin 35, 5.0 kg (69.4 mol) of acrylic acid and 2.91 kg (83.1 kg) of methyl alcohol containing 0.2% by weight of water and 8.3% by weight of methyl acrylate were added per hour.
Hydroquinone corresponding to 0.05% by weight based on the acrylic acid in the stock solution is present in the reaction stock solution consisting of
It was mixed with 11.87Kg and supplied. The mixed solution thus supplied to this reaction tank was methyl acrylate9.1
14.2% by weight of methyl alcohol, 52.7% by weight of acrylic acid, and 23.9% by weight of water, by-products, etc., and the amount was 19.78 kg/hour. The reaction tank was placed in a hot water bath, and the temperature inside the reaction tank was maintained at 80°C. In this reaction tank, 99% of the acrylic acid in the newly supplied reaction stock solution was converted to methyl acrylate.

The reaction product taken out from the reaction tank was sent to a distillation column, and 9.77 kg/hour of methyl acrylate containing 0.02% by weight of hydroquinone was supplied from the top of the column, and distilled at normal pressure. At this time, the tower top temperature was 69°C and the pot temperature was 102°C. In this way, 17.53 kg of distillate was obtained from the top of the column per hour, and its composition was 90.5% by weight of methyl acrylate and methyl alcohol.
2.5% by weight, water 7.0% by weight, and acrylic acid
It was 0.0005% by weight or less. On the other hand, 12.02 kg of bottom liquid was extracted every hour from the distillation column, and 2.4 kg of this was sent to a thin film evaporator to remove high-boiling substances, polymers, etc., and then mixed with the remaining 9.62 kg and circulated to the reaction tank.

The distillate from the distillation column was sent to an oil-water separation tank and separated into a methyl acrylate phase and an aqueous phase. The methyl acrylate phase was separated from methyl alcohol and water in a light separation column and sent to a rectification column to obtain methyl acrylate. On the other hand, the aqueous phase was mixed with methyl alcohol and water separated in the light fraction separation tower, sent to an alcohol recovery tower to remove most of the water, and circulated to the reaction tank. As a result, the yield of methyl acrylate based on the acrylic acid used was 97.8%, and the recovery rate of methyl alcohol was 99%.

Example 2 In the same manner as in Example 1, 5.0 acrylic acid per hour
Kg (69.4 mol) with 7.6 wt% water and 4.8 wt%
Ethyl alcohol containing ethyl acrylate of 4.38
Hydroquinone corresponding to 0.05% by weight based on the acrylic acid in the stock solution was added to the reaction stock solution consisting of Kg (83.3 mol), and this was mixed with the circulating liquid from the distillation column liquid at 23.45 Kg per hour. Then, a strongly acidic cation exchange resin 70 was filled and supplied to a reaction tank maintained at 80°C.

Thus, the mixed solution supplied to the reaction tank contained 16.7% by weight of ethyl acrylate and 13.0% by weight of ethyl alcohol.
42.3% by weight of acrylic acid, and 27.9% by weight of water, by-products, etc., and the amount was 32.83 kg/hour. In this reaction tank, 98% of the acrylic acid in the newly supplied reaction stock solution was converted to ethyl acrylate.

The reaction product taken out from the reaction tank was sent to a distillation column, and ethyl acrylate containing 0.02% by weight of hydroquinone was supplied from the top of the column at a rate of 2.72 kg per hour, and distilled at normal pressure. At this time, the tower top temperature was 79°C and the pot temperature was 110°C. In this way, 11.93 kg of distillate was obtained from the top of the column per hour, and its composition was 81.6% by weight of ethyl acrylate and ethyl alcohol.
5.4% by weight, water 13.0% by weight, and acrylic acid
It was 0.0005% by weight or less. On the other hand, 23.62 kg of liquid from the distillation column was extracted every hour, and 2.36 kg of this was sent to a thin film evaporator to remove high-boiling substances, polymers, etc., and then mixed with the remaining 21.26 kg and circulated to the reaction tank.

The distillate from the distillation column was sent to an oil-water separation tank and separated into an ethyl acrylate phase and an aqueous phase. The ethyl acrylate phase was separated from ethyl alcohol and water in a light fraction separation column and sent to a rectification column to obtain ethyl acrylate. On the other hand, the aqueous phase was mixed with ethyl alcohol and water separated in a light fraction separation tower, sent to an alcohol recovery tower to remove most of the water, and circulated to the reaction tank. As a result, the yield of ethyl acrylate based on the acrylic acid used was 97.5%, and the recovery rate of ethyl alcohol was 98.6%.

Example 3 5.0 methacrylic acid per hour in the same manner as in Example 1
Kg (58.1 mol) with 0.4 wt% water and 1.3 wt%
Methyl alcohol containing methyl methacrylate
Hydroquinone corresponding to 0.05% by weight of methacrylic acid in the stock solution is present in the reaction stock solution consisting of 2.27Kg (69.6mol), and this is mixed with 36.35Kg/hour of circulating fluid from the distillation column liquid to react with a strong acid. The reactor was filled with cation exchange resin 90 and supplied to a reaction tank maintained at 80°C.

Thus, the mixed liquid supplied to the reaction tank contained 43.8% by weight of methyl methacrylate and 6.8% by weight of methyl alcohol.
It consisted of 43.6% by weight of methacrylic acid and 5.7% by weight of water, by-products, etc., and was 43.62 kg/hour. In this reaction tank, 99% of the methacrylic acid in the newly supplied reaction stock solution was converted to methyl methacrylate.

The reaction product taken out from the reaction tank was sent to a distillation column, and methyl methacrylate containing 0.02% by weight of hydroquinone was supplied from the top of the column at a rate of 3.57 kg per hour, and distilled at normal pressure. At this time, the tower top temperature was 85°C and the pot temperature was 110°C. In this way, 10.71 kg of distillate was obtained from the top of the column per hour, and its composition was 86.8% by weight of methyl methacrylate and methyl alcohol.
3.5% by weight, water 9.7% by weight, and methacrylic acid
It was 0.0005% by weight or less. On the other hand, 36.48 kg of bottom liquid was extracted every hour from the distillation column, and 3.65 kg of this was sent to a thin film evaporator to remove high-boiling substances, polymers, etc., and then mixed with the remaining 32.83 kg and circulated to the reaction tank.

The distillate from the distillation column was sent to an oil-water separation tank and separated into a methyl methacrylate phase and an aqueous phase. The methyl methacrylate phase was separated from methyl alcohol and water in a light fraction separation column and sent to a rectification column to obtain methyl methacrylate.

On the other hand, the aqueous phase was mixed with methyl alcohol and water separated in the light fraction separation tower, sent to an alcohol recovery tower to remove most of the water, and circulated to the reaction tank. As a result, the yield of methyl methacrylate based on the methacrylic acid used was 97.5%, and the recovery rate of methyl alcohol was 99.5%.

[Brief explanation of the drawing]

FIG. 1 is a process flow sheet suitable for practicing the present invention.

Claims (1)

[Claims] 1 Acrylic acid or methacrylic acid with 1 or more carbon atoms
When producing an acrylic acid ester or a methacrylic acid ester by esterifying the lower aliphatic alcohol of No. 3 in the presence of an acidic catalyst, the molar ratio of the acrylic acid or methacrylic acid to be supplied as a raw material and the alcohol is 1:1.0 to 1.0. 2.0, and the esterification reaction is carried out at a temperature of 60 to 100°C.
When the resulting esterification reaction mixture is distilled, the water concentration in the resulting distillate is 3 to 8% by weight in the case of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, or In the case of isopropyl methacrylate, the acrylic ester or methacrylic ester is newly supplied to the distillation column from outside the system so that the concentration ranges from 8 to 13.5% by weight, thereby substantially converting the acrylic acid or methacrylic acid. The distillate consisting of acrylic ester or methacrylic ester, esterification reaction product water, and unreacted alcohol is concentrated, and the distillation column liquid from which the product water has been substantially removed is recycled to the esterification reaction. A method for producing an acrylic ester or a methacrylic ester, characterized by: