JP6094258B2 - Method for producing (meth) acrylic acid ester - Google Patents

Description

  The present invention relates to a method for producing (meth) acrylic acid ester, and in particular, esterification reaction containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst. In the method of producing a (meth) acrylic acid ester by sequentially feeding the oil phase obtained by neutralizing and washing the liquid, followed by oil-water separation to a light boiling separation tower and a purification tower, The present invention relates to a method for producing a (meth) acrylic acid ester stably and efficiently over a long period of time by preventing a distillation operation trouble.

  In the present specification, (meth) acrylic acid is a general term for acrylic acid and methacrylic acid, and either one or both of them may be used.

  (Meth) acrylic acid ester is a compound having polymerizability, and can give excellent properties to the resulting polymer, so that it can be used in various applications such as paints, adhesives, pressure-sensitive adhesives, synthetic resins, fibers, etc. It is widely used as a raw material.

  As a method for producing (meth) acrylic acid ester, a method in which (meth) acrylic acid and an alcohol are esterified in the presence of an acid catalyst is generally widely used. Further, in order to remove the acid catalyst and unreacted (meth) acrylic acid from the obtained esterification reaction solution, the oil layer is extracted with water and then treated with an alkaline aqueous solution, and then contains (meth) acrylic acid ester. In general, the organic layer is separated from the aqueous layer containing water and neutralized salt generated by such washing and neutralization treatment in a stationary tank (for example, Patent Document 1). ).

  FIG. 2 is a system diagram showing a conventional process for producing a general acrylate ester, in which acrylic acid and alcohol undergo an esterification reaction through an esterification reactor 1 in the presence of an acid catalyst, and an esterification reaction is performed. The water produced in is discharged from the esterification reactor 1 to the outside of the system. The esterification reaction solution is countercurrently contacted with water in the extraction tower (catalyst recovery tower) 2 to extract and recover the acid catalyst, and a part of the recovered catalyst is circulated to the inlet side of the esterification reactor 1. The remaining portion is fed to the subsequent heavy cracker 7 where it is used for the heavy cracking or esterification reaction in the heavy cracker 7. The reaction solution from the extraction tower 2 is neutralized by adding an alkaline aqueous solution in the acrylic acid separation tower 3 and washed with water. The neutralized and washed treatment liquid from the acrylic acid separation tower 3 is separated into oil and water in the stationary tank 4, the aqueous phase is discharged out of the system, and the oil phase is fed to the next light boiling separation tower 5 and unreacted. The light boiling components such as alcohol are distilled and separated from the top of the column. The bottom liquid of the light boiling separation tower 5 is fed to the next purification tower 6 where the heavy components are separated by distillation, and the high-purity acrylic ester of the product is taken out from the top of the tower. The bottom liquid of the purification tower 6 is sent to the heavy cracker 7, where acrylic acid, acrylic acid ester and alcohol are produced by decomposition and distillation of heavy components, and these valuable materials are circulated in the reactor. The bottom liquid of the heavy cracker 7 is discharged out of the system as waste oil.

  FIG. 3 is another system diagram showing a conventional process for producing a general acrylic ester. Acrylic acid and alcohol undergo an esterification reaction through an esterification reactor 1 in the presence of a solid acid catalyst, Water produced by the esterification reaction is discharged out of the system from the esterification reactor 1. The esterification reaction liquid is neutralized by adding an alkaline aqueous solution in the acrylic acid separation tower 3 and washed with water. The neutralized and washed treatment liquid from the acrylic acid separation tower 3 is separated into oil and water in the stationary tank 4, the aqueous phase is discharged out of the system, and the oil phase is fed to the next solvent recovery tower (solvent separation tower) 8. Then, the solvent is separated by distillation, and then fed to the light boiling separation column 5 where light boiling components such as unreacted alcohol are distilled and separated from the top of the column. The bottom liquid of the light boiling separation tower 5 is fed to the next purification tower 6 where the heavy components are separated by distillation, and the high-purity acrylic ester of the product is taken out from the top of the tower. The bottom liquid of the purification tower 6 is sent to the heavy cracker 7, where acrylic acid, acrylic acid ester and alcohol are produced by decomposition and distillation of heavy components, and these valuable materials are circulated in the reactor. The bottom liquid of the heavy cracker 7 is discharged out of the system as waste oil.

  Conventionally, in the production of (meth) acrylic acid ester, in order to separate and remove by-products such as polymer and sludge, an oil-water mixture at the oil-water interface in the neutralization of the esterification reaction solution, the washing step and the oil-water separation step is used. Extraction is proposed in Patent Document 2, but in Patent Document 2, the extracted oil / water mixture is not returned to the (meth) acrylic ester production process.

JP 2003-231665 A JP 2003-226672 A

In the (meth) acrylic acid ester manufacturing process, alkali metal salts derived from sodium hydroxide, etc., used for neutralization of the esterification reaction solution are brought in, resulting in contamination of distillation towers such as light-boiling separation towers in the latter stage. There was a problem that the distillation performance deteriorated.
That is, by neutralizing (meth) acrylic acid using a basic compound such as sodium hydroxide, an alkali metal salt such as (meth) acrylic acid sodium salt is produced, and when this is brought into a subsequent distillation system, The alkali metal salt of (meth) acrylic acid adheres to the packing or the like in the distillation column and hinders stable operation of the distillation column. Specifically, in the acrylic ester production process, the distillation separation performance of alcohol or the like in the light boiling separation column deteriorates, and alcohol or the like is mixed into the acrylic ester of the product.
In this case, it is necessary to stop the operation and wash the inside of the light boiling separation tower or replace the packing, so that long-term continuous operation cannot be performed, and the productivity is significantly reduced.

  The present invention solves the above-mentioned conventional problems, and in such a (meth) acrylic ester production process, (meth) acrylic ester prevents the trouble of distillation operation caused by an alkali metal salt in a light boiling separation tower. It is an object to provide a manufacturing method.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that when the polymer coexists in the interface region between the oil layer and the water layer in the neutralization, washing process and oil-water separation process, Therefore, the oil / water mixture in the interface region between the oil layer and the water layer is withdrawn, and the extracted oil / water mixture is allowed to stand for a predetermined time, and then the oil phase is returned to the process. By doing so, it has been found that alkali metal can be prevented from being brought into the light boiling separation tower, and trouble in distillation operation of the light boiling separation tower caused by the alkali metal salt can be prevented.
In addition, as in Patent Document 2, it is possible to prevent the alkali metal from being brought into the light boiling separation tower by extracting the oil / water mixture from the neutralization, washing process and oil / water separation process. By simply withdrawing the liquid, valuable materials such as (meth) acrylic acid ester and unreacted alcohol contained in the oil / water mixture are discarded as waste liquid, resulting in deterioration of the basic unit.

  The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] An esterification reaction liquid containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst in a reactor is converted into a (meth) acrylic acid separation tower. Neutralizing and washing with, leaving the neutralized and washed treatment liquid in a stationary tank to separate oil and water, and introducing the resulting oil phase into a light boiling separation tower to remove light boiling components including alcohol In the method for producing a (meth) acrylic acid ester containing an oil / water mixture, an oil / water mixture in the interface region between the oil layer and the water layer in the (meth) acrylic acid separation tower and / or the stationary tank is extracted, and the oil / water mixture is separately added. after then fed to a storage tank provided on standing predetermined time and oil-water separation, characterized in that to return the oil phase to the reactor (meth) acrylic acid ester.

[2] The method for producing a (meth) acrylic acid ester according to [1], wherein the oil / water mixed solution is allowed to stand for 2 hours or more in the storage tank.

[3] The process for producing a (meth) acrylic acid ester according to [1] or [2], wherein the alkali metal concentration of the oil phase returned to the reactor is 400 ppm or less.

  According to the present invention, after neutralizing and washing an esterification reaction solution containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst, oil-water separation is performed. In the method of producing (meth) acrylic acid ester by sequentially feeding the oil phase obtained in this way to the light boiling separation tower and the purification tower, the trouble of distillation operation caused by alkali metal salt in the light boiling separation tower is prevented. In addition, a stable and efficient (meth) acrylic acid ester can be produced over a long period of time.

It is a systematic diagram of the manufacturing process of the acrylic ester which shows embodiment of the manufacturing method of the (meth) acrylic ester of this invention. It is a systematic diagram which shows an example of the manufacturing process of a general acrylic ester. It is a systematic diagram which shows another example of the manufacturing process of a general acrylate ester.

  Hereinafter, embodiments of the method for producing a (meth) acrylic acid ester of the present invention will be described in detail.

  The method for producing a (meth) acrylic acid ester of the present invention is an esterification containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst in a reactor. The reaction liquid is neutralized and washed with a (meth) acrylic acid separation tower, the neutralized and washed treatment liquid is left in a stationary tank for oil-water separation, and the resulting oil phase is lightly boiled from a packed tower. In the method for producing a (meth) acrylic acid ester, which includes a step of removing a light boiling component containing alcohol by introducing it into a separation tower, the interface between the oil layer and the water layer in the (meth) acrylic acid separation tower and / or a stationary tank The oil / water mixture in the region is extracted, and the extracted oil / water mixture is supplied to a separately provided storage tank (hereinafter sometimes referred to simply as “storage tank”) and allowed to stand for a predetermined time to separate the oil and water. In reactor and / or (meth) acrylic acid separation column Characterized in that it sent.

  That is, the esterification reaction liquid contains polymers such as poly (meth) acrylic acid and poly (meth) acrylic acid ester by-produced by the esterification reaction of (meth) acrylic acid and alcohol. Polymers such as polybutyl acrylate have a butyl group that is a hydrophobic group, and polyacrylic acid has a carboxyl group that is a hydrophilic group, so these may coexist or form a copolymer. In the case of neutralization in an acrylic acid separation tower, washing, and when oil-water separation is performed in a stationary tank, it exists in the interface region between the oil layer and the water layer. A part of the polymer in the oil / water interface region is contained in the aqueous phase and discharged out of the system as waste water, but most of the polymer is contained in the oil phase in a form that includes water droplets in the carboxyl group portion, which is a hydrophilic group. Brought to the boiling separation tower. And when alkali metal such as sodium is contained in the water droplets contained in this polymer and brought into the light boiling separation tower, alkali metal salt is deposited on the surface of the filler in the light boiling separation tower, and this is deposited. By doing so, the stable operation of the light boiling separation column is hindered.

  For this reason, in this invention, the oil-water liquid mixture of the oil-water interface area | region in a (meth) acrylic acid separation tower and / or a stationary tank is extracted. The extracted oil / water mixture is separated into oil / water again when allowed to stand in a storage tank for a predetermined time, so that the separated oil phase is returned to the reactor and / or the (meth) acrylic acid separation tower. That is, the aqueous phase contains an alkali metal salt, and the vicinity of the interface contains a lot of alkali metal salt and the above-mentioned polymer, while the oil phase contains (meth) acrylic acid ester, unreacted alcohol, reaction by-products, Since the Michael adduct such as alkyl alkoxypropionate that can be decomposed and recovered as a valuable material by being decomposed in the heavy decomposing device at the later stage is contained, the oil phase is returned to the production process of (meth) acrylic acid ester. To collect them.

  In the present invention, if the amount of the oil / water mixture extracted from the (meth) acrylic acid separation tower and / or the stationary tank is too small, the effect of the present invention by extracting the oil / water mixture cannot be sufficiently obtained, On the other hand, if the amount is too large, no further improvement in the effect can be obtained, and a large-capacity storage tank for leaving the extracted liquid is required, and it is not preferable in terms of the circulating energy of the liquid. Therefore, the extraction amount of the oil / water mixture from the (meth) acrylic acid separation tower is the esterification reaction liquid supplied to the (meth) acrylic acid separation tower (usually the ester from which the acid catalyst has been extracted and separated in the extraction tower). 0.05 to 10% by weight, particularly 0.1 to 5% by weight with respect to the reaction solution. For the same reason, the extraction amount of the oil / water mixture from the stationary tank is also 0.05 to 10% by weight, particularly 0.1 to 5%, based on the esterification reaction solution supplied to the (meth) acrylic acid separation tower. It is preferable to set it as weight%.

The standing time of the oil / water mixture in the storage tank is not particularly limited, but the oil phase returned to the esterification reactor and / or the (meth) acrylic acid separation tower (hereinafter sometimes referred to as “returned oil phase”). .) Is preferably left standing for a time when the alkali metal concentration is 400 ppm or less, particularly 100 ppm or less, particularly 10 ppm or less, and the standing time is usually 2 hours or more, for example, 2 to 72 hours. If the alkali metal concentration in the return oil phase is too high, a distillation operation trouble in the light boiling separation tower cannot be prevented reliably. The alkali metal concentration of the return oil phase is preferably as low as possible, but is usually 1 ppm or more.
If the standing time in the storage tank is too short, it will not be possible to sufficiently reduce the alkali metal concentration of the return oil phase by sufficiently separating the oil and water. This is not preferable because the storage capacity for standing still increases.

The return from the storage tank to the esterification reactor and / or the (meth) acrylic acid separation tower needs to be carried out only in the oil phase. For that purpose, the lower aqueous layer is discharged from the nozzle at the lower part of the tank in advance and then the upper part is removed. Return only the oil phase. The amount of the aqueous phase discharged is determined depending on the case where only the oil / water mixture extracted from the oil / water interface of the (meth) acrylic acid separation tower and / or the stationary tank is introduced into the storage tank, and other places such as esters. Oil-water mixing extracted from the (water) interface of the (meth) acrylic acid separation tower and / or the stationary tank, unlike the case where a liquid mainly composed of an oil phase from a polymerization reactor or a purification tower is introduced Since it varies depending on the ratio of oil to water in the liquid, it is adjusted as appropriate according to the situation.
A plurality of storage tanks may be used, and drainage of the aqueous phase may be performed while standing.

  Below, the more specific manufacturing method of the (meth) acrylic acid ester of this invention is demonstrated with reference to FIG.

  FIG. 1 is a system diagram of an acrylic ester production process showing an embodiment of a method for producing a (meth) acrylic ester of the present invention. The manufacturing process shown in FIG. 1 is different from the manufacturing process shown in FIG. 2 in that the storage tank 10 is provided, and the other configuration is the same. In FIG. 1, members having the same functions as those shown in FIG. However, the manufacturing method of the (meth) acrylic acid ester of the present invention is not limited to the manufacturing process shown in FIG. 2, but the manufacturing process shown in FIG. 3 and other (meth) acrylic acid and alcohol in the presence of an acid catalyst. After neutralizing and washing the esterification reaction solution containing (meth) acrylic acid ester obtained by the reaction, the oil phase obtained by oil-water separation is sequentially fed to a light boiling separation tower and a purification tower. In the method for producing a (meth) acrylic acid ester, a storage tank can be provided as shown in FIG.

  The (meth) acrylic acid ester produced in the present invention is not particularly limited, and is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic acid n-. Examples include hexyl, n-octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Among these, (meth) acrylic acid alkyl esters having 4 or more carbon atoms in the alkyl group such as n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are preferable.

  In the production of a (meth) acrylic acid ester, the corresponding ester is generally produced from (meth) acrylic acid and an alcohol through an esterification reactor 1 in the presence of an acid catalyst. Usually, (meth) acrylic acid and alcohol as raw materials are supplied to the reactor at a molar ratio of 1.0: 0.5 to 1.0: 2.0. As the acid catalyst, p-toluenesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, organic acids such as methanesulfonic acid, and mineral acids such as sulfuric acid and hydrochloric acid are used. The acid catalyst is added in an amount of 0.1 to 5.0% by weight, preferably 1.0 to 2.5% by weight, based on the reaction solution. The reaction is carried out at a temperature of 70 to 180 ° C. while removing the reaction product water produced by the esterification reaction by distillation or azeotropic distillation (reactive distillation method). An azeotropic agent inert to the reaction may be added to facilitate removal of product water. As the azeotropic agent, hydrocarbons such as benzene, toluene and cyclohexane are often used. The reaction product water may be removed by a method other than membrane separation such as a vapor separation membrane or a vaporization membrane, or distillation.

  In addition, a polymerization inhibitor is usually added to the reaction system in order to prevent the formation of a polymer. Examples of polymerization inhibitors include phenols such as hydroquinone and hydroquinone monomethyl ether, amines such as phenothiazine and diphenylamine, heavy metal salts such as copper dibutyldithiocarbamate and manganese acetate, nitroso compounds, nitro compounds, tetramethylpiperidinooxyl derivatives, etc. The aminoxyls are known. The addition amount of the polymerization inhibitor is preferably such that the concentration of the polymerization inhibitor in the esterification reaction solution is about 20 to 1000 ppm.

  The esterification reaction solution is countercurrently contacted with water in the extraction tower (catalyst recovery tower) 2 to extract and recover the acid catalyst, and a part of the recovered acid catalyst is circulated to the inlet side of the esterification reactor 1. The remaining portion is sent to the heavy decomposer 7 and used for the heavy decomposition in the subsequent heavy decomposer 7. The reaction liquid from the extraction tower 2 is neutralized by adding an alkaline aqueous solution in the acrylic acid separation tower 3 and washed with water, and then sent to the stationary tank 4 from the top of the acrylic acid separator 3. The oil and water are separated.

  The ratio of water counter-contacted with the esterification reaction liquid in the extraction tower 2 is preferably 0.5 (weight ratio) or less with respect to the esterification reaction liquid, and optimally 0.05 to 0.2 (weight ratio). It is. Although water may be newly added, the reaction product water obtained from the esterification reactor 1 can also be used. In this case, there is an advantage that the amount of waste water can be reduced.

  As the form of the extraction tower 2, a normal one can be used. A general extraction tower supplies an esterification reaction liquid from the bottom of the tower, extraction water from the top of the tower, and a reaction liquid from which the acid catalyst has been extracted and removed from the top of the tower. Although it is a type which obtains the aqueous solution containing acrylic acid etc., it does not restrict | limit in particular. As the extraction tower, a packed tower, a plate tower and the like are generally used, but an apparatus having a high liquid-liquid contact efficiency is preferable. The extraction tower may be provided in a single stage or multiple stages.

  As the acrylic acid separation tower 3, the same one as the extraction tower 2 can be used. Examples of the aqueous alkali solution used for neutralization include aqueous solutions of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In order to neutralize the esterification reaction liquid containing acidic water-soluble impurities and completely remove these impurities, an alkaline aqueous solution is supplied so that the pH of the neutralized acrylic acid-containing liquid is 9 or more It is preferable.

  An esterification reaction liquid (hereinafter referred to as “neutralization / washing treatment liquid”) after neutralization and washing in the acrylic acid separation tower 3 to remove acidic water-soluble impurities such as (meth) acrylic acid. ) Is extracted from the top of the acrylic acid separation tower 3, and the water used for neutralization and washing is discharged out of the system as waste water from the bottom of the tower. Water may be further added to the neutralization / washing treatment liquid from the acrylic acid separation tower 3 in order to increase the removal efficiency of alkali metals in the neutralization / washing treatment liquid. Be sent. If the amount of water added to the neutralization / cleaning solution is too small, the effect of improving the alkali metal removal efficiency cannot be sufficiently obtained, and if it is too large, no further improvement in effect can be expected. However, it is industrially disadvantageous because the liquid volume increases. Accordingly, the amount of water to be added is usually 0 to 100% by weight, preferably 1 to 10% by weight, and more preferably 2 to 6% by weight with respect to the neutralization / cleaning treatment liquid.

  The water to be added to the neutralization / cleaning treatment liquid may be any water that does not contain a high concentration of a new contamination source such as a metal component, and industrial water, pure water, steam condensed water, or the like can be used.

  The neutralization / cleaning treatment liquid to which water is added as necessary is then left in the stationary tank 4 to be separated into oil and water, the aqueous phase is discharged out of the system as waste water, and the oil phase is light boiling separation tower 5 The light boiling components such as alcohol are distilled and separated from the top of the column, and the top distillate is circulated to the reactor 1. On the other hand, the high-boiling fraction of the column bottom liquid is further separated by distillation in the purification column 6, and the product acrylic acid ester is separated from the column top. The bottom liquid of the purification tower 6 is processed by the heavy cracker 7, valuables are circulated to the reaction system, and the bottom liquid is discharged out of the system as waste oil. That is, the column bottom liquid of the purification column 6 contains Michael adducts such as alkyl alkoxypropionate by-produced in the esterification reaction step of acrylic acid and alcohol. The acid catalyst (recovered acid catalyst from the extraction tower 2 in FIG. 1) and acrylic acid are added and decomposed and separated by distillation to recover valuable materials such as alcohol and acrylic ester. These are circulated in the reaction system.

  The light boiling separation column 5 and the purification column 6 may be any as long as they are usually used as a distillation column, and a packed column is preferably used. The heavy cracker 7 may be anything as long as it is normally used as a distillation apparatus, and a drum for simple distillation is preferably used.

  From the alkaline acid separation tower 3 and the stationary tank 4, the oil / water mixture is extracted from the interface region between the oil layer and the water layer, respectively, and the extracted oil / water mixture is supplied to the storage tank 10 and allowed to stand for a predetermined time. The oil and water are separated. The oil layer separated in the storage tank 10 is returned to the esterification reactor 1, and the aqueous phase is discharged out of the system as waste water. In FIG. 1, the oil phase from the storage tank 10 is returned to the esterification reactor 1, but may be returned to the acrylic acid separation tower 3. Further, it may be returned to both the esterification reactor 1 and the alkaline acid separation tower 3, but in general, when returned to the acrylic acid separation tower 3, there is a risk of causing fluctuations in the interface. It is preferable to return to the chemical reaction reactor 1.

  During the above operation, an organic layer and / or an aqueous layer extracted during neutralization, washing, and standing are generated. Occur and these are extracted out of the process (stream). These extracted liquids from the process contain valuable materials such as unreacted raw materials, while the organic layer contains a polymer and the aqueous layer contains an alkali metal salt, and both concentrate at the organic layer / aqueous layer interface. If these are re-introduced into the process when the extracted liquid is circulated into the process, it may cause deterioration of operation, so care must be taken when circulating the extracted liquid into the process. It is.

  In the present invention, the extracted liquid may be circulated after standing in the storage tank 10 and separating the oil and water, treating the oil layer with a heavy cracker.

  According to the present invention, it is possible not only to prevent the alkali metal from being brought into the light boiling separation tower 5, but also to prevent the polymer produced as a by-product from the esterification reaction. Since this polymer also inhibits stable operation in the light boiling separation column 5, according to the present invention, troubles in distillation operation due to the polymer can be prevented, and stable and efficient (meth) acrylic over a long period of time. Production of acid esters can be performed.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  In the following, the sodium concentration of the oil phase was determined by performing atomic absorption analysis after adding pure water at a volume ratio of 1: 1 to the sample to extract sodium. The concentrations of butyl acrylate, n-butanol and butyl butoxypropionate were measured by gas chromatography.

[Example 1]
By using a combination of phenothiazine and hydroquinone as a polymerization inhibitor and p-toluenesulfonic acid as an acid catalyst, butyl acrylate was produced by the production process shown in FIG.
Acrylic acid and n-butanol were used in a molar ratio of 1: 1. Further, p-toluenesulfonic acid was used at 1.3% by weight with respect to the reaction solution, and the reaction temperature was 95 ° C.
The outlet liquid 13 t / hr of the esterification reactor 1 is fed to the extraction tower 2, washed and extracted with 1200 kg / hr of water, then fed to the acrylic acid separation tower 3 at 13 t / hr, and 25 wt% hydroxylation The solution was neutralized with 150 kg / hr of an aqueous sodium solution and 400 kg / hr of water and washed with water. The composition of the reaction solution supplied from the extraction tower 2 to the acrylic acid separation tower 3 was 87% by weight of butyl acrylate, 6% by weight of n-butanol, and 4% by weight of butyl butoxypropionate. 400 kg / hr of water is added to this neutralization / cleaning treatment liquid 13 t / hr, oil-water separation is performed in the stationary tank 4, and the oil phase is sequentially distilled in the light boiling separation tower 5 and the purification tower 6 to obtain butyl acrylate as a product. Got. From the acrylic acid separation tower 3 and the stationary tank 4, an oil / water mixture at the interface region between the oil layer and the water layer was extracted at 30 kg / hr and fed to the storage tank 10. In the storage tank 10, after leaving the non-standard process liquid at the start of the reaction and the out-of-process extracted liquid such as the process extracted liquid at the time of stopping the reaction for 50 t, the oil phase is 200 kg / hr. Was returned to the esterification reactor 1, and the aqueous phase was extracted from a nozzle provided at the bottom of the storage tank 10 and discharged out of the system as waste water.
The composition of this return oil phase was 89% by weight of butyl acrylate, 6% by weight of n-butanol, 3% by weight of butyl butoxypropionate, and the sodium concentration was 6.2 ppm.
When the operation was performed in this manner, continuous operation could be stably performed for 85 days without causing trouble in distillation operation of the light boiling separation column 5.

DESCRIPTION OF SYMBOLS 1 Esterification reactor 2 Extraction tower 3 Acrylic acid separation tower 4 Stationary tank 5 Light boiling separation tower 6 Purification tower 7 Heavy cracker
8 Solvent recovery tower 10 Storage tank

Claims (3)

Esterification reaction solution containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst in the reactor is neutralized with a (meth) acrylic acid separation tower. , Washing, neutralizing and washing the solution in a stationary tank and separating it into oil and water, and introducing the resulting oil phase into a light boiling separation tower to remove light boiling components including alcohol ( In the method for producing a (meth) acrylic ester,
The oil / water mixture in the interface region between the oil layer and the water layer in the (meth) acrylic acid separation tower and / or the stationary tank is withdrawn, and the oil / water mixture is fed to a separate storage tank and allowed to stand for a predetermined time. And then separating the oil and water , and then returning the oil phase to the reactor.   The method for producing a (meth) acrylic acid ester according to claim 1, wherein the oil / water mixture is allowed to stand for 2 hours or more in the storage tank. Method for producing a (meth) acrylic acid esters according to claim 1 or 2, wherein the alkali metal concentration of the oil phase is returned to the reactor is less than 400 ppm.

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