JP2019156738A - Production method of (meth)acrylic acid ester - Google Patents

Abstract

To provide a method of producing (meth)acrylic acid ester stably and efficiently over a long term by separating (meth)acrylic acid ester and a heavy component from an esterification reaction liquid containing (meth)acrylic acid ester obtained by reacting (meth)acrylic acid and alcohol under the presence of an acid catalyst, by preventing formation of an origin of contamination at an operation start time of a heavy decomposer that recovers valuable matters by decomposing and causing an esterification reaction of the heavy component, and by effectively reflecting condition adjustment for contamination/closure during an operation thereafter.SOLUTION: When recovering valuable matters containing (meth)acrylic acid ester and alcohol by decomposing, and making esterification reaction by introducing a mixed liquid of the heavy component and an acid catalyst-containing liquid in the heavy decomposer, introduction of the heavy component into the heavy decomposer is started, and after an internal temperature has reached 80°C or higher by heating, the acid catalyst solution is supplied to the heavy decomposer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing (meth) acrylic acid ester, and in particular, an esterification reaction liquid containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst. The (meth) acrylic acid ester is separated from the heavy component, and the heavy component is sent to the heavy cracker for decomposition and esterification to recover valuable materials. (Meth) acrylic acid ester is produced stably and efficiently over a long period of time by preventing the formation of the starting point of dirt at the start and effectively reflecting the adjustment of conditions for preventing dirt and blockage during the subsequent operation. Regarding the method.

  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. 1 is a system diagram showing a conventional process for producing a typical acrylate ester. 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 liquid is countercurrently contacted with water in the extraction tower (catalyst recovery tower) 2 to extract, separate and recover the acid catalyst, and a part of the recovered catalyst is recycled to the esterification reactor 1 for reuse. Is done. The remaining portion is fed to the subsequent heavy cracker 7 and may be used for the decomposition and recovery of heavy components in the heavy cracker 7. The reaction solution from the extraction tower 2 is neutralized by adding an alkaline aqueous solution in the neutralization washing tower 3. In some cases, water may be supplied separately for cleaning. The neutralized and washed treatment liquid from the neutralization washing 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 fed to the heavy cracker 7, where acrylic acid, acrylic acid ester and alcohol are produced by decomposition and distillation of heavy components. , It is circulated to the upstream process such as the neutralization washing tower 3. The bottom liquid of the heavy cracker 7 is discharged out of the system as waste oil. In the figure, 7A is a reboiler of the heavy cracker 7.

  That is, the bottom liquid of the purification tower 6 contains alkyl alkoxypropionate, alkyl hydroxypropionate, alkyl maleate, dimerization product of acrylic acid, esters thereof, and the like, which are by-produced in the esterification reaction step of acrylic acid and alcohol. Therefore, the column bottom liquid is fed to the heavy cracker 7 and decomposed by adding an acid catalyst solution. Valuables such as alcohol, alkyl acrylate, and acrylic acid are collected and circulated through the reactor 1, the extraction tower 2, the neutralization washing tower 3, and the like. In addition to the above components, the bottom liquid of the purification tower 6 includes phenols such as hydroquinone and hydroquinone monomethyl ether, amines such as phenothiazine and diphenylamine, copper dibutyldithiocarbamate, acetic acid supplied in the esterification reactor 1. One or more polymerization inhibitors selected from heavy metal salts such as manganese, nitroso compounds, nitro compounds, aminoxyls such as tetramethylpiperidinooxyl derivatives and the like are included. In addition, the heavy decomposer 7 includes acrylic acid and a liquid extracted outside the process of the manufacturing process (a non-standard process liquid at the start of the reaction, a process liquid extracted when the reaction is stopped, an acrylic acid separation tower, and an oil / water interface of the stationary tank. In some cases, an organic layer and / or an aqueous layer from which only the organic layer is separated is also introduced and treated.

  FIG. 2 is another system diagram showing a conventional general process for producing an acrylate ester, in which 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 solution is neutralized by adding an alkaline aqueous solution in the neutralization washing tower 3. In some cases, water may be separately supplied to be washed. The neutralization and washing treatment liquid from the neutralization washing 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 sent 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 fed to the heavy cracker 7, where acrylic acid, acrylic acid ester and alcohol are produced by decomposition and distillation of heavy components. Then, it is circulated to an upstream process such as the neutralization washing tower 3, and the bottom liquid of the heavy cracker 7 is discharged out of the system as waste oil. In the figure, 7A is a reboiler of the heavy cracker 7.

  That is, as described above, the bottom liquid of the purification tower 6 includes Michael such as alkyl maleate, alkyl dimer acid, alkyl alkoxypropionate, alkyl hydroxypropionate, etc., which are by-produced in the esterification reaction step of acrylic acid and alcohol. Since the adduct is contained, the bottom liquid is fed to the heavy cracker 7, acid catalysts are added from outside the system to decompose them, and the esterification reaction and distillation separation are performed. Valuables such as alcohol, alkyl acrylate, and acrylic acid are recovered and circulated through the reactor 1, the neutralization washing tower 3, and the like. In addition to the above components, the bottom liquid of the purification tower 6 includes phenols such as hydroquinone and hydroquinone monomethyl ether, amines such as phenothiazine and diphenylamine, copper dibutyldithiocarbamate, acetic acid supplied in the esterification reactor 1. One or more polymerization inhibitors selected from heavy metal salts such as manganese, nitroso compounds, nitro compounds, aminoxyls such as tetramethylpiperidinooxyl derivatives and the like are included. In addition, as described above, the heavy decomposer 7 includes acrylic acid and a liquid extracted from outside the process of the manufacturing process (a non-standard process liquid at the start of the reaction, a process liquid extracted at the time of stopping the reaction, an acrylic acid separation tower, In some cases, an organic layer extracted from the oil / water interface of the tank and / or an aqueous layer separated only from the organic layer) is introduced and treated.

  In such a (meth) acrylic acid ester production process, in a heavy cracker that decomposes heavy components and recovers valuables, (meth) acrylic acid, (meth) acrylic ester polymer, acid catalyst Contaminant substances such as deposits from the origin caused problems such as blockage of the pipes attached and a decrease in the heat transfer efficiency of the reboiler, which hindered stable operation.

In Patent Document 2, the acid catalyst concentration in the acid catalyst-containing liquid supplied to the heavy cracker is 28% by weight or less, and the acid catalyst concentration in the liquid mixture with the heavy component is 1 to 3% by weight. It has been shown that by operating in this manner, the formation of soil-causing substances during heavy cracker operation can be suppressed.
Further, Patent Document 3 describes a method in which a liquid flow in the circumferential direction is generated in the heavy decomposer and the solid matter that causes the blockage of the pipe is extracted without being deposited.
In Patent Document 4, as a method for producing a (meth) acrylic acid ester that prevents troubles in distillation operation in a light boiling separation tower, the polymer concentration in the introduction liquid of the light boiling separation tower is set in the operation period of the light boiling separation tower. In a period of 70% or more, a method of 200 ppm or less, or a temperature increase rate of the reactor of 20 ° C./hr or less in a temperature range of 70% or more of the total temperature rise temperature or a time of 70% or more of the total temperature rise time It is described that.

JP 2003-231665 A JP 2014-162767 A Japanese Patent Laid-Open No. 2004-43451 JP 2014-162663 A

  However, in pipes and heat exchangers attached to heavy crackers, a small amount of (meth) acrylic acid or its ester polymer is the starting point of soiling, so that polymerization / precipitation proceeds at an accelerated rate. Occlusion may be promoted, and in such a state, it was impossible to stop the progress of dirt even if the condition adjustment during operation was precisely performed by the methods described in Patent Documents 2 to 4. In particular, in the process of repeating the operation start / stop operation, the conventional condition adjustment during operation is insufficient to reliably prevent the progress of dirt in each operation.

  The present invention suppresses the formation of dirt substances at the start of operation of the heavy cracker in the production process of (meth) acrylic acid ester, and stably suppresses dirt every time even in a continuous process in which the operation is started and stopped repeatedly. It is an object of the present invention to provide a method for producing a (meth) acrylic acid ester.

In order to solve the above-mentioned conventional problems, the present inventor is important not to form a starting point of dirt at the start of operation of the heavy decomposer, and for that purpose, the acid catalyst solution is contained in the heavy decomposer. It has been found that the temperature may be supplied when the temperature becomes a predetermined temperature or higher.
Usually, when treating a compound having polymerizability such as (meth) acrylic acid or (meth) acrylic acid ester, it is not preferable to perform rapid heating from the viewpoint of generation of contamination due to the formation of a polymer. In particular, acid tends to promote polymerization, and in the production process of (meth) acrylic acid ester that is heated in the presence of an acid catalyst, special attention must be paid to suppression of polymerization.
For example, in Patent Document 4, in a method for producing a (meth) acrylic acid ester, in an esterification reactor that performs heating under the presence of an acid catalyst in order to keep the amount of polymer produced to be a certain amount or less, It is shown that the rate of temperature rise is set to a certain rate or less.
Considering the above cases, it is presumed that, even in the operation of the heavy cracker, it is preferable to perform heating with a moderate heat load after supplying the acid catalyst solution. However, the results of the study conducted by the inventor are contrary to expectations. Rather, the acid catalyst solution is supplied in a state where the temperature inside the cracker is high by heating in advance, and the acid catalyst solution is rapidly heated. It was found that this is effective in preventing dirt.

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

[1] A reaction step in which (meth) acrylic acid and alcohol are reacted in the presence of an acid catalyst to obtain an esterification reaction liquid containing a (meth) acrylic acid ester, and (meth) acrylic acid from the esterification reaction liquid A purification step for separating the ester and the heavy component, supplying the acid catalyst solution and the heavy component to the heavy decomposer, and decomposing the heavy component with the acid catalyst solution in the heavy decomposer, Introducing the heavy component into the heavy decomposer in a method for producing a (meth) acrylic ester comprising a recovery step of recovering a valuable material including a (meth) acrylic ester and alcohol Then, after the internal temperature reaches 80 ° C. or higher by heating, the method for producing a (meth) acrylic acid ester, in which the acid catalyst solution is supplied to the heavy decomposer.

[2] The method for producing a (meth) acrylic acid ester according to [1], wherein the acid catalyst solution contains water as a solvent.

[3] (Meta) according to [1] or [2], wherein when the internal temperature of the heavy decomposer is 80 ° C. or higher, the acid catalyst solution and (meth) acrylic acid are supplied to the heavy decomposer. A method for producing an acrylic ester.

  According to the present invention, in the (meth) acrylic acid ester manufacturing process, the formation of the starting point of dirt at the start of operation of the heavy decomposer for recovering valuable materials from the heavy component separated from the (meth) acrylic acid ester It is possible to effectively and stably reflect the adjustment of conditions for dirt and blockage during the subsequent operation, and to produce a (meth) acrylic acid ester stably and efficiently over a long period of time.

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 includes a reaction step of reacting (meth) acrylic acid and an alcohol in the presence of an acid catalyst to obtain an esterification reaction liquid containing a (meth) acrylic acid ester, A purification step for separating the (meth) acrylic acid ester and the heavy component from the esterification reaction solution, an acid catalyst solution and the heavy component are supplied to the heavy decomposer, and the acid decomposer is used in the heavy decomposer. A method for producing a (meth) acrylic acid ester comprising a recovery step of recovering a valuable material including a (meth) acrylic acid ester and an alcohol by decomposing and esterifying the heavy component with a catalyst solution. The introduction of the heavy component into the cracker is started, and after the internal temperature reaches 80 ° C. or higher by heating, the acid catalyst solution is supplied to the heavy cracker.

That is, the present inventor can suppress the formation of the starting point of dirt at the start of operation in the heavy cracker by supplying the acid catalyst solution after the internal temperature of the heavy cracker is raised to 80 ° C. or higher. I found a good thing.
Regarding the mechanism that can suppress the formation of the starting point of dirt at the start of operation of the heavy decomposer by supplying the acid catalyst-containing liquid after the internal temperature of the heavy decomposer is raised to 80 ° C. or higher, Is estimated as follows.
The feed liquid supplied to the heavy cracker, that is, the heavy component and the acid catalyst-containing liquid, (meth) acrylic acid and the out-of-process discharge liquid may be mixed in advance and then supplied to the heavy cracker. May be supplied separately.
In a steady state where the temperature in the heavy cracker is 150 to 200 ° C., these feed liquids are mixed in the heavy cracker and have a uniform liquid composition in the accompanying piping and heat exchanger. It is considered that the polymerization inhibitor contained in each solution is also uniformly distributed.
However, if these supply liquids are supplied in a state where the temperature at the start of operation is low, mixing is considered to be insufficient depending on the supply ratio and supply speed. In addition to the polymerizable compounds such as (meth) acrylic acid and (meth) acrylic acid ester, the supply liquid contains an acid catalyst that promotes polymerization, a polymerization inhibitor that inhibits polymerization, and the like. It is considered that when each of the above components is unevenly distributed and a composition having high polymerizability is locally formed, a polymer serving as a starting point of dirt is formed.
According to the method of the present invention, since the acid catalyst solution is supplied when the temperature in the heavy cracker is 80 ° C. or higher, the solvent such as water contained in the acid catalyst solution evaporates quickly, and the liquid mixing property Expected to improve the effect. Further, although it is not preferable that the acid catalyst is unevenly distributed to promote polymerization, an effect of preventing the uneven distribution is also expected by supplying the acid catalyst after the inside of the cracker has a uniform composition. Furthermore, it is presumed that the solubility of the acid catalyst is increased by setting the temperature to 80 ° C. or higher, and uneven distribution due to precipitation or the like is prevented. In addition, an effect of preventing polymerization acceleration is expected by supplying the acid catalyst after the polymerization inhibitor contained in the heavy component is uniformly dispersed in the decomposer. According to the present invention, it is presumed that the result of preventing the generation of the starting point of dirt was obtained by these combined effects.

  In this invention, an acid catalyst solution refers to the liquid containing an acid catalyst among the liquid introduce | transduced into the heavy decomposer 7, and 18 liquid in FIG.1 and FIG.2 corresponds. In FIG. 1, the acid catalyst solution may be a part of the 12 acid catalyst recovery liquids extracted from the bottom of the extraction tower 2 or may be separately prepared and supplied. The acid catalyst solution is usually an aqueous solution of an acid catalyst having a concentration of about 10 to 30% by weight. The heavy component is a heavy component distilled and separated from (meth) acrylic acid ester, and corresponds to the bottom liquid of the purification column 6 in FIGS. The heavy decomposer 7 is introduced with this heavy component, an acid catalyst solution, and (meth) acrylic acid or a liquid extracted outside the process.

  In the present invention, the temperature in the heavy cracker is raised at the start of operation of the heavy cracker, and the acid catalyst solution is introduced after the temperature in the heavy cracker reaches 80 ° C. or higher. In normal cases, the heavy component is introduced into the heavy decomposer prior to the introduction of the acid catalyst solution, and the heavy decomposer solution is circulated between the reboiler and the heavy decomposer. Raise the temperature. In the present invention, introduction of the acid catalyst solution is started when the internal temperature of the heavy decomposer becomes 80 ° C. or higher by heating with the reboiler of the heavy decomposer.

When the acid catalyst solution is introduced into the heavy cracker when the internal temperature of the heavy cracker is less than 80 ° C., as described above, a highly polymerizable composition is locally formed, and the origin of contamination A material is formed.
The higher the internal temperature of the heavy decomposer when the acid catalyst solution is supplied to the heavy decomposer, the higher the temperature is 80 ° C. or higher, the easier it is to suppress the formation of dirt substances, so the internal temperature of the heavy decomposer is 100 ° C. or higher, particularly 130 ° C. When it becomes above, it is preferable to start introduction of the acid catalyst solution into the heavy cracker.
However, if the internal temperature of the heavy decomposer is excessively high, easily polymerizable compounds such as (meth) acrylic acid and (meth) acrylic acid ester are excessively heated in the absence of an acid catalyst necessary for the decomposition reaction. As a result, the polymerization reaction becomes dominant and conversely promotes the formation of a soiling substance. In addition, since the internal temperature of the heavy decomposer during normal operation is about 150 to 200 ° C. as described later, the internal temperature of the heavy decomposer at the start of introduction of the acid catalyst solution into the heavy decomposer is 200 ° C. or less, In particular, the temperature is preferably 170 ° C. or lower.

  In the present invention, (meth) acrylic acid may be supplied together with the supply of the acid catalyst solution to the heavy cracker. That is, by introducing (meth) acrylic acid together with the acid catalyst solution when the internal temperature of the heavy cracker reaches 80 ° C or higher, preferably 100 ° C or higher, particularly preferably 130 to 170 ° C, A locally highly polymerizable composition can be prevented from being formed, and the formation of a soiling substance can be further suppressed.

  In any case, by preventing the acid catalyst solution from being present in the low-temperature heavy cracker, it is possible to prevent the formation of a locally highly polymerizable composition in the heavy cracker and its associated equipment. Thus, the formation of dirt substances can be suppressed.

  The present invention can be carried out according to a conventional method except that the internal temperature of the heavy cracker at the start of the supply of the acid catalyst solution to the heavy cracker is set to a predetermined temperature or higher as described above.

  Below, the general manufacturing method of (meth) acrylic acid ester is demonstrated with reference to FIG. 1, but the manufacturing method of (meth) acrylic acid ester of this invention is not restricted to the manufacturing process shown in FIG. 2, (meth) acrylic acid ester from an esterification reaction solution containing (meth) acrylic acid ester obtained by reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst. And the heavy component can be distilled and separated, and the heavy component can be fed to a heavy decomposer to be decomposed and esterified to recover valuable materials.

  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 3.0% by weight, based on the reaction solution. The reaction is carried out at a temperature of 70 to 140 ° 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 liquid 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 recycled to the esterification reactor 1 for reuse. Is done. The remainder is fed to the subsequent heavy decomposer 7 and may be used for heavy component decomposition in the heavy decomposer 7. The reaction solution from the extraction tower 2 is neutralized by adding an alkaline aqueous solution in the neutralization washing tower 3 and washed with water, and then sent to the stationary tank 4 from the top of the neutralization washing tower 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 with high liquid-liquid contact efficiency is preferable. The extraction tower may be provided in a single stage or multiple stages.

  As the neutralization washing tower 3, the same thing 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 neutralization washing tower 3 to remove acidic water-soluble impurities such as (meth) acrylic acid. ) Is extracted from the top of the neutralization washing 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 neutralization washing 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 a heavy cracker together with an acid catalyst solution (preferably an acid catalyst recovery liquid from the extraction tower 2 is used), acrylic acid from the raw material tank, and if necessary, a liquid extracted outside the process. 7 is supplied. These supply liquids may be supplied to the heavy decomposer 7 using the same supply pipe, or may be supplied using separate pipes attached to the heavy decomposer 7. After the feed liquid is introduced into the heavy decomposer 7, the Michael adducts and the like in the heavy component are decomposed and esterified. The supply amount of the acid catalyst solution is preferably 5 to 20% by weight with respect to the supply amount of the bottom liquid of the purification tower 6. The acid catalyst concentration in the acid catalyst solution is preferably 10 to 40% by weight, particularly preferably 10 to 30% by weight. The amount of acrylic acid supplied is preferably 0 to 20% by weight with respect to the amount of the bottom liquid supplied to the purification tower 6, and the amount of liquid extracted outside the process is 0 to 50% with respect to the amount of the bottom liquid supplied to the purification tower 6. % Is preferred. In the present invention, at the start of operation of the heavy decomposer 7, as described above, the acid catalyst solution or the acid catalyst solution and acrylic acid are supplied after the temperature of the heavy decomposer 7 is increased. Valuables including alkyl acrylate, alcohol, acrylic acid and the like produced by the esterification reaction in the heavy cracker 7 are extracted from the top of the column. This valuable material is returned to the esterification reactor 1, the extraction tower 2, or the neutralization washing tower 3. On the other hand, the bottom liquid of the heavy cracker 7 is discharged out of the system as waste oil. In addition, since the extracted liquid outside the process has a composition different from that of the acid catalyst solution, there is no particular limitation on the internal temperature of the heavy decomposer when it is supplied to the heavy decomposer.

  Although there is no restriction | limiting in particular about the operating conditions of this heavy decomposer 7, Usually, reaction temperature 150-200 degreeC and reaction pressure 90-100 kPa are employ | adopted. Regarding the method of heating the internal solution of the heavy cracker 7, any method such as a method of circulating the internal solution to the reboiler and heating, a method of installing a jacket type heater outside, a method of inserting a heater inside the decomposer, etc. Although a method can be adopted, in order to prevent local heating and make the liquid composition uniform, a method in which the internal liquid is circulated through the reboiler and heated is particularly preferable. Moreover, although there is no restriction | limiting in particular in the quantity of the tower bottom liquid extracted as waste oil, Usually, it is preferable to set it as about 10-40 weight% conditions with respect to the liquid mixture introduce | transduced into the heavy cracker 7. FIG. The residence time in the heavy decomposer calculated from (the amount of liquid retained in the heavy decomposer / reboiler and associated piping) / (amount of column bottom liquid) is preferably 5 to 15 hours. In addition, according to this condition, the concentration of water in the heavy cracker internal solution is 1% by weight or less, and this has the effect of assisting the uniform internal liquid composition. Internal liquids 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 and tetramethylpiperidinooxyl derivatives It is preferable that the polymerization inhibitor concentration is 0.1 to 10% by weight. The polymerization inhibitor may be supplied in a state of being contained in the supply liquid, or may be added separately. The composition of the heavy cracker internal solution is obtained by extracting the column bottom liquid and analyzing it.

  In FIG. 1, the bottom liquid of the purification tower 6 obtained by sequentially treating the esterification reaction liquid in the extraction tower 2, the neutralization washing tower 3, the stationary tank 4, the light boiling separation tower 5, and the purification tower 6 is obtained. Is decomposed by the heavy decomposer 7, but the heavy component decomposed in the heavy decomposer in the present invention is separated from the (meth) acrylic acid ester by distillation from the esterification reaction solution. What is necessary is just a mass, and it is not limited to what passed through the process shown by FIG.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the density | concentration of each compound described in an Example is quantified by analyzing each component of a heavy part by gas chromatography, and an acid catalyst solution by liquid chromatography.

[Example 1]
In the butyl acrylate production process shown in FIG. 1 for producing butyl acrylate from acrylic acid and butanol, the heavy fraction extracted from the bottom of the purification tower 6 is introduced into the heavy cracker 7 for heavy decomposition. A portion of the bottoms of the vessel 7 was heated by the reboiler 7A and circulated to the heavy cracker 7 to carry out heating. When the internal temperature of the heavy cracker 7 becomes 130 ° C. to 140 ° C. by the heating, acrylic acid from the raw material tank and the acid catalyst recovery liquid extracted from the bottom of the extraction tower 2 are used as the acid catalyst solution. Each was sent to the heavy cracker 7 to continuously perform heavy decomposition, esterification reaction, and distillation separation. The amount of acrylic acid and the acid catalyst solution fed to the heavy cracker 7 was 1/8 by weight with respect to the heavy content fed to the heavy cracker 7A. The heavy content contained 45 wt% butyl β-butoxypropionate, 43 wt% butyl acrylate, 5 wt% butyl dimer (butyl ester of acrylic acid dimer). The acid catalyst solution was a 15% by weight p-toluenesulfonic acid aqueous solution.
Thereafter, the internal temperature was raised to 170 ° C. and maintained at a constant temperature, and continuous operation was carried out for 15 hours from the start of feeding of acrylic acid and the acid catalyst solution. The heavy cracker top pressure during operation was 100 kPa, and the residence time in the heavy cracker was 6 hours. The water concentration in the bottoms was 1% by weight or less. When the inside of the reboiler 7A was inspected after the operation, the amount of adhered dirt was less than 5 mg.

[Example 2]
When the internal temperature of the heavy cracker 7 reaches 130 ° C. to 140 ° C. by supplying heavy components to the heavy cracker 7 and heating by the reboiler 7A, an acid catalyst is supplied to the heavy cracker 7. This was carried out in the same manner as in Example 1 except that the supply of only 1/8 of the recovered liquid by weight to the heavy component was started.
When the inside of the reboiler was inspected after 15 hours of operation, the amount of attached dirt was less than 5 mg.

[Comparative Example 1]
This was carried out in the same manner as in Example 1 except that the supply of acrylic acid and the acid catalyst recovery liquid was started when the internal temperature of the heavy cracker 7 was 40 ° C.
When the inside of the reboiler was inspected after 15 hours of operation, the amount of attached dirt was 100 mg.

[Comparative Example 2]
This was carried out in the same manner as in Example 2 except that the supply of only the acid catalyst recovery liquid was started when the internal temperature of the heavy cracker 7 was 40 ° C.
When the inside of the reboiler was inspected after 15 hours of operation, the amount of attached dirt was 40 mg.

  From the results of Examples 1 and 2 and Comparative Examples 1 and 2 above, the supply of the acid catalyst solution, or the acid catalyst solution and (meth) acrylic acid to the heavy cracker 7, It can be seen that by performing the heating after raising the temperature to 80 ° C. or higher, it is possible to suppress the formation of dirt substances on the reboiler 7A of the heavy cracker 7.

DESCRIPTION OF SYMBOLS 1 Esterification reactor 2 Extraction tower 3 Neutralization washing tower 4 Standing tank 5 Light boiling separation tower 6 Purification tower 7 Heavy cracker 7A Reboiler 8 Solvent recovery tower 9 (Meth) acrylic acid 10 Alcohol 11 Acid catalyst 12 Acid catalyst Recovery liquid 13 Alkaline aqueous solution 14, 15 Wash water 16 Light boiling separation component 17 Purified (meth) acrylic acid ester 18 Acid catalyst solution 19 (Meth) acrylic acid 20 Extracted liquid outside process 21 Decomposition recovery component 22 Heavy decomposition residue 23 Solvent recovery component

Claims (3)

  A reaction step of reacting (meth) acrylic acid and alcohol in the presence of an acid catalyst to obtain an esterification reaction liquid containing (meth) acrylic acid ester; and (meth) acrylic acid ester and A purification step for separating the mass, and supplying the acid catalyst solution and the heavy fraction to the heavy cracker, and the heavy catalyst is decomposed and esterified by the acid catalyst solution in the heavy cracker In the method for producing a (meth) acrylic acid ester, which includes a recovery step of recovering a valuable material containing a (meth) acrylic acid ester and an alcohol, the introduction of the heavy content into the heavy decomposer is started and heated. (Meth) acrylic acid ester manufacturing method of supplying the acid catalyst solution to the heavy decomposer after the internal temperature reaches 80 ° C. or higher.   The method for producing a (meth) acrylic acid ester according to claim 1, wherein the acid catalyst solution contains water as a solvent.   The production of a (meth) acrylic acid ester according to claim 1 or 2, wherein the acid catalyst solution and (meth) acrylic acid are supplied to the heavy decomposer when the internal temperature of the heavy decomposer is 80 ° C or higher. Method.

Images