Method for producing ethyl acrylate

Abstract

To provide a method of simplifying a process, and further improving esterification reaction and decomposition and recovery efficiency of an addition reaction product while reducing danger of generating polymerization occlusion in production of ethyl acylate with acrylic acid and ethanol as raw materials using a fixed bed reactor filled with a solid catalyst of a cation exchange resin.SOLUTION: A method for producing ethyl acrylate includes: an esterification reaction process of feeding acrylic acid and ethanol to a fixed bed reactor filled with a cation exchange resin to continuously obtain a reaction mixture by esterification reaction; a dehydration distillation process of feeding the reaction mixture to an azeotropic dehydration distilling tower having an azeotropic solvent to separate into a crude ethyl acrylate and a low-boiling matter; and a purification process of making the crude ethyl acrylate into ethyl acrylate by a purification distilling tower, where the azeotropic solvent is a hydrocarbon having a boiling point under a normal pressure of 55°C-75°C.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing ethyl acrylate. The present invention relates to a method for producing ethyl acrylate by an esterification reaction using the above as a raw material. [Background technology]

[0002] Acrylic esters are used in the manufacture of water-based paints, adhesives, synthetic resins, fibers, emulsions, etc. It is an easily polymerizable monomer used in the general-purpose esthetics industry and is the main ingredient in these products. General-purpose esters are classified into general-purpose esters and special esters that are added to improve the functionality of products. are usually methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl acrylate Also, methyl acrylate and ethyl acrylate are collectively referred to as light acrylate. Ester, butyl acrylate and 2-ethylhexyl acrylate together form heavy ester Acrylic esters are produced from acrylic acid and alcohol. esterification reaction using acrylic ester and alcohol as raw materials, transesterification reaction using acrylic ester and alcohol as raw materials, Instead of acrylic acid, acrolein, acrylic anhydride, or acrylic acid halide is used. These compounds can be synthesized by various synthetic routes, such as addition or substitution reactions of these compounds with alcohols. In the case of esters for use in polymers, esterification reaction is carried out using acrylic acid and alcohol, which are inexpensive raw materials. is usually the manufacturing method of choice.

[0003] In the esterification reaction using acid and alcohol as raw materials, the reaction product ester and by-product water are Since there is a hydrolysis reaction with ethylenediamine, i.e., a reverse reaction, the conversion rate of the esterification reaction is The reaction only reaches an equilibrium state that depends on the liquid composition, and if a certain amount of raw material remains in the reaction liquid, In contrast, the by-product water is separated from the reaction system at the same time as the esterification reaction is carried out. By separating the two, the reaction conversion rate can be increased. When producing butyl acrylate, the esterification reaction is carried out in the liquid phase while the by-product water is distilled off. The reaction distillation is used to produce acrylic acid from acrylic acid and 2-ethylhexanol. The same is true for producing 2-ethylhexyl acetate. When producing ethyl acrylate, if reactive distillation is carried out in the same manner as above, the raw material ethanol The boiling point is lower than that of the by-product water, and ethanol is infinitely miscible with water, so by-product water is not added to the system. In the process of discharging the ethanol to the outside, the ethanol is also discharged to the outside. In the batchwise reactive distillation of acrylic acid and ethanol as raw materials, carbon dioxide was used as an azeotropic solvent. Using a mixed solvent of hydrocarbons with number 6 or 7 and ethyl acetate, the distillate was separated into an aqueous phase and an oil phase, and the oil A method has been shown to obtain high reaction conversion by circulating the phase as reflux to the distillation column.

[0004] In the continuous process for the production of ethyl acrylate, a strongly acidic ion exchange resin is used as a catalyst. In Non-Patent Document 1, acrylic acid and alcohol are reacted in a fixed bed using ion exchange. a reaction step in which the reaction solution is supplied to a fixed-bed reactor filled with an ion exchange resin and subjected to an esterification reaction; The resulting mixture was distilled to separate the acrylic acid ester, water, and unreacted alcohol into distillate components and unreacted acrylic acid ester. an ester recovery step of separating the distillate into a bottoms solution containing carboxylic acid and recycling the bottoms solution to the reactor; The alcohol in the extract is extracted with water, and the alcohol in the extracted aqueous solution is separated by distillation. The alcohol recovery process, water, alcohol, and acetate esters contained in the raffinate after extraction A low boiling point separation process in which low boiling point components such as ethanol are distilled off, and the liquid separated from the light boiling point components is distilled. and a purification step of obtaining a product acrylic ester. is shown.

[0005] Patent Document 2 also describes a divided wall column (DWC) having a vertical partition wall in a distillation column. By using a sieving wall column, low-boiling impurities and high-boiling impurities can be separated. A method is shown in which crude ethyl acrylate is purified using a single distillation column. In Patent Document 3, a strongly acidic ion exchange resin is used as a fixed bed catalyst to produce acrylic acid and a carbon number A method has been shown to increase the reaction conversion rate by reacting alcohols 1 to 3 under reduced pressure. There are. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 59-67244 [Patent Document 2] Special Publication No. 2019-504078 [Patent Document 3] Japanese Patent Application Publication No. 10-279523 [Non-patent literature]

[0007] [Non-Patent Document 1] Ullmann's Encyclopedia of Industrial Chemistry 5th.ed. vol.1A pp167-169 Summary of the Invention [Problem to be solved by the invention]

[0008] In the production of ethyl acrylate using acrylic acid and ethanol as raw materials, In the above-mentioned method, the catalyst concentration in the reaction liquid is lower than that in a fixed-bed reactor, and the reaction takes a long time. In addition, the distillate contains a large amount of ethanol, and the bottoms of the reactor contain acrylic acid ethanol. In addition to chill, raw acid, alcohol, and ethyl acetate are also contained, so separation and recovery processes for these are also required. It is economically viable in terms of the heat load required for distillation and purification and the cost of constructing the necessary facilities. It is disadvantageous. The method described in Non-Patent Document 1 is a common method used in commercial production of ethyl acrylate. However, although the process is simply to separate and purify the product of the esterification reaction, Further improvement is desired in this respect. The method described in Patent Document 2 combines the low boiling point separation step and purification step of Non-Patent Document 1 into one. However, its practical application is limited to the above processes, and its effects are also limited. is. The raw material acrylic acid and the product ethyl acrylate are easily polymerizable compounds that spontaneously initiate polymerization. This is the biggest reason why the manufacturing process cannot be simplified. Since the boiling point is much higher than that of ethanol and ethyl acrylate, if we consider only the boiling point, Separation and concentration by distillation is considered easy. However, in reality, the low temperature method is required to avoid polymerization. Therefore, it is recovered containing a large amount of ethyl acrylate.

[0009] Copper complexes are highly effective polymerization inhibitors for acrylic acid and acrylic esters. However, these compounds are all cation exchange compounds. These polymerization inhibitors are poisonous to the cation exchange resin, so they are used as catalysts for the polymerization of cation exchange resins. It is not usually used in the area where it circulates to the reactor. If it is used, it is necessary to exchange the cation exchange resin. In order to prevent deterioration, a large excess of cation exchange resin is packed into the reactor. It is necessary to Furthermore, the carbon double bonds of acrylic acid and ethyl acrylate are Since the addition reaction of water and the like occurs in parallel with the esterification reaction, the production of the addition reaction product is suppressed and Decomposition and recovery are required. Decomposition is carried out at high temperatures in the presence of an acid catalyst, so the addition reaction product must be removed in advance. However, it is preferable to separate and concentrate the ethyl acrylate. The boiling point of ethyl cypropionate is only about 20°C different from that of acrylic acid, so To increase the yield, an additional distillation step is required.

[0010] In view of these circumstances, the present invention uses acrylic acid and ethanol as raw materials and a cationic solid catalyst. In the production of ethyl acrylate using a fixed-bed reactor packed with an ion-exchange resin, polymerization This simplifies the process while reducing the risk of blockage due to esterification and addition reactions. The object of the present invention is to provide a method for increasing the efficiency of decomposition and recovery of reactants. [Means for solving the problem]

[0011] As a result of extensive research into solving this problem, the inventors of the present invention have found that a fixed bed using a cation exchange resin In the production of ethyl acrylate using a reactor for esterification, the reaction liquid produced is By performing dehydration distillation using a hydrocarbon with a constant boiling point as an azeotropic solvent, ethyl acrylate It eliminates the need for an extraction process in the manufacturing process, eliminates restrictions on the use of polymerization inhibitors, and This resulted in improved decomposition and recovery efficiency of the reactants. That is, the present invention provides the following.

[0012] [1] Acrylic acid and ethanol are fed into a fixed-bed reactor packed with a cation exchange resin. an esterification reaction step of continuously obtaining a reaction solution by an esterification reaction, The crude ethyl acrylate is fed to an azeotropic dehydration distillation column in the presence of a solvent, and separated into crude ethyl acrylate and low boiling points. a distillation step, and a purification step of converting the crude ethyl acrylate into ethyl acrylate in a purification distillation column. 1. A method for producing ethyl acrylate comprising: ℃ to 75℃ for the production of ethyl acrylate, a hydrocarbon. [2] Acrylic acid and ethanol are fed into a fixed-bed reactor packed with cation exchange resin. an esterification reaction step of continuously obtaining a reaction solution by an esterification reaction, The resulting mixture is fed to an azeotropic dehydration distillation column in the presence of a solvent, where it is separated into crude ethyl acrylate 1 and low boiling points 1. The crude ethyl acrylate 1 is supplied to a low boiler separation column in which an azeotropic solvent is present, and the crude ethyl acrylate is a dehydration distillation step in which the crude ethyl acrylate 2 is separated into crude ethyl acrylate 2 and low boiling points 2; A method for producing ethyl acrylate, comprising a purification step of converting the ethyl acrylate into ethyl acrylate, The azeotropic solvent is a hydrocarbon having a boiling point of 55°C to 75°C at atmospheric pressure, and the crude acrylic acid ethylene The concentration of water, ethanol and azeotropic solvent in the chiller 1 is 20% by mass or less. Method for producing ethyl acetate. [3] The low boiling point material is separated into an oil phase and an aqueous phase, and the oil phase is recycled to the azeotropic dehydration distillation column. The method for producing ethyl acrylate described above. [4] The low boiling point material 1 is separated into an oil phase and an aqueous phase, and the oil phase is recycled to the azeotropic dehydration distillation column. [2] 1. The method for producing ethyl acrylate according to claim 1 . [5] Ethanol is recovered from the aqueous phase, and the recovered ethanol is supplied to a fixed-bed reactor. [4] The method for producing ethyl acrylate according to [4]. [6] [1] to [2], wherein a polymerization inhibitor is used in the dehydration distillation step and / or the purification step. 5] The method for producing ethyl acrylate according to any one of [1] to [5]. [7] The polymerization inhibitor is selected from the group consisting of phenothiazine, copper complexes, and manganese complexes. The method for producing ethyl acrylate according to [6], wherein the method comprises at least one of the following steps: [Effects of the Invention]

[0013] According to the present invention, the continuous production process of ethyl acrylate is simplified and the polymerisation-induced plugging is prevented. This reduces the risk of generation of chlorine, and makes decomposition and recovery of the adduct more efficient. This became possible. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of a conventional process for producing ethyl acrylate. [Figure 2] FIG. 1 is a schematic diagram showing an example of a process for producing ethyl acrylate according to the present invention. [Figure 3] FIG. 1 is a schematic diagram showing another example of the process for producing ethyl acrylate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The method of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the description, and various modifications can be made within the scope of the gist of the present invention. Cut.

[0016] [Conventional process] FIG. 1 is a schematic diagram showing an example of a conventional process for producing ethyl acrylate. The dotted line indicates that the main component of the process fluid is water. Acid (AA) and raw material ethanol (EtOH) were heated and then poured into a cation exchange resin filled with The reaction liquid discharged from the fixed bed reactor is fed to a dehydration distillation column (R11). The overhead distillate gas is condensed and separated into two liquid phases. The reflux liquid is circulated to the dehydration distillation column (C11), and the remainder is fed to the bottom of the extraction column (C12). The lower phase of the two liquid phases is fed to the ethanol recovery column (C15). Part of the liquid is concentrated in an evaporator (V11) and then fed to a thermal decomposition device (R12), and the remaining The outflow is recycled to the fixed bed reactor (R11). Water or an aqueous solution is extracted from the top of the extraction column (C12). The aqueous ethanol solution is extracted from the bottom of the column and fed to the ethanol recovery column (C15). Ethanol is recovered from the top of the ethanol recovery column (C15) and fed to a fixed bed reactor (R11). The crude ethyl acrylate is extracted from the top of the extraction column (C12) and separated into low boiling points. The low boiling point material is separated in the column (C13), and then purified acrylic acid is separated in the purification distillation column (C14). Ethyl acetate (EA) is obtained. In the conventional process, the dehydration distillation column (C11) alone is not enough to separate water and ethanol from the reaction mixture. Since it was difficult to separate the ethanol solution, it was necessary to further separate the ethanol solution using an extraction column (C12). There was a need.

[0017] [Invention 1] Fig. 2 is a schematic diagram showing an example of the process for producing ethyl acrylate according to the present invention. Acid (AA) and raw material ethanol (EtOH) were heated and then poured into a cation exchange resin filled with The reaction liquid discharged from the fixed bed reactor is fed to the fixed bed reactor (R21). It is fed to the middle stage of the existing azeotropic dehydration distillation column (C21). It is fed to the azeotropic dehydration distillation column (C21). A sufficient amount of azeotropic solvent is circulated as a reflux liquid relative to the water and ethanol present in the reaction liquid. By this, low boiling points such as the azeotropic solvent, ethanol, and water are distilled from the top of the column, and azeotropic dehydration is performed. Ethyl acrylate, acrylic acid, and high-boiling addition products are extracted from the bottom of the distillation column (C21). However, depending on the operation fluctuations, crude ethyl acrylate containing ethanol, etc. can be extracted. Since there is a possibility that the azeotropic dehydration distillation column (C21) may be mixed into the bottom of the column, 1) 0.1 to 10 mass% of ethyl acrylate based on the total amount of ethyl acrylate discharged from the bottom of the column It is preferable to set the conditions so that ethyl acetate is also distilled off from the top of the azeotropic distillation column for dehydration (C21).

[0018] The cation exchange resin is not particularly limited by the resin properties such as the resin structure and crosslink density. Various cation exchange resins can be used, among which macroporous strongly acidic cation exchange resins are preferred. Anion exchange resins are preferred. As macroporous strongly acidic cation exchange resins, Amb erlist TM —13wet, Amberlist TM -16wet (above, DuPont nt Co., Ltd.), Diaion TM -208LH, Diaion TM -216H, Diaio n TM -216LH, Diaion TM -228LH (all manufactured by Mitsubishi Chemical Corporation) These cation exchange resins may be used alone or in combination of two or more.

[0019] The azeotropic solvent is a hydrocarbon having a boiling point of 55°C to 75°C at normal pressure. The upper limit of the boiling point is preferably 70°C. By having a boiling point within the above range, low boiling points such as water and ethanol can be separated from the reaction solution. It is possible to increase the efficiency of separation and recovery. However, a mixture of multiple hydrocarbons may be used. When a mixture of elements is used, its boiling point is the temperature at which the vapor pressure of the mixture becomes 1 atmosphere, or the temperature at which the vapor-liquid balance This is the temperature calculated by equilibrium calculation.

[0020] The condensate of the overhead distillate gas from the azeotropic dehydration distillation column (C21) is mainly composed of hydrocarbons, which are the azeotropic solvent. The upper phase is separated into an upper phase consisting mainly of ethanol and water, and a lower phase consisting mainly of ethanol and water. The lower phase is fed to the dehydration distillation column (C21) as the ethanol recovery column (C25), and the lower phase is fed to the column (C26). The ethanol recovered from the top is recycled to the fixed bed reactor (R21), and the bottoms are treated as wastewater. The bottoms of the azeotropic dehydration distillation column (C21) are fed to the middle of the purification column (C24), and From the bottom of the column, acrylic acid, ethyl acrylate, and the addition reaction product are obtained. The distillate is extracted from the evaporator (V21) and fed to the fixed bed reactor (R21). The bottoms are circulated and fed to the thermal decomposition unit (R22). The cracked distillate is recycled to the evaporator (V21) or other upstream processes. The bottom liquid from 2) is disposed of as waste oil.

[0021] In the azeotropic dehydration distillation column (C21), crude ethyl acrylate and low boiling points are separated from the reaction mixture. When carrying out the azeotropic distillation for dehydration, it is preferable that a polymerization inhibitor is present in the azeotropic distillation column for dehydration. The inhibitor is supplied to the azeotropic dehydration distillation column together with the reaction liquid, but is also supplied to the azeotropic dehydration column via a dedicated supply line. However, from the viewpoint of ease of mixing with the reaction liquid, it is preferable to feed the reaction mixture to the distillation column. It is preferable that the distillation column be supplied with the liquid to the azeotropic dehydration distillation column. In addition, when crude ethyl acrylate is purified in the distillation column, the polymerization inhibitor is present. The polymerization inhibitor is preferably phenothiazine, copper complex, or manganese. The presence of at least one compound selected from the group consisting of the group consisting of the cation complexes is effective in inhibiting polymerization and preventing polymerization. This is preferable from the viewpoint of reducing the risk of blockage due to the pores. However, if these polymerization inhibitors are contained in an excessive amount in the ethyl acrylate after distillation purification, the acrylate This polymerization is prohibited because it may cause problems in the production of derivatives made from ethyl acrylate. The agent or a liquid containing the agent is discharged from the top of the distillation purification column from which the purified ethyl acrylate is discharged. It is preferably fed at the bottom.

[0022] [Invention 2] FIG. 3 is a schematic diagram showing another example of the process for producing ethyl acrylate according to the present invention. The difference between the two is that in Figure 2, there is only one azeotropic dehydration distillation column (C21) from the fixed bed reactor to the purification distillation column. In contrast, in Figure 3, there are two columns: an azeotropic dehydration column (C31) and a low boiler separation column (C33). The column configuration and the fixed bed reactor in Figure 2 are one unit (R21), while in Figure 3 is a fixed bed reactor (R31a) dedicated to raw acrylic acid and raw ethanol, and recovered acrylic acid and a fixed bed reactor (R31b) dedicated to recovering ethanol.

[0023] Although Figure 3 has the disadvantage of increasing the number of devices, it has the advantages described below. Before being sent to the final purification distillation column, the reaction liquid is passed through an azeotropic dehydration distillation column (C31), a low boiler separation column (C 33), the operating conditions of the azeotropic dehydration distillation column (C31) are adjusted by adjusting the degree of pressure reduction. The operating conditions such as adjusting the temperature at the bottom of the column can be relaxed, and the crude ethyl acrylate 1 contained in the bottom liquid of the column can be reduced. The concentration of water, ethanol and azeotropic solvent contained therein is 20% by mass or less, and 15% by mass or less % or less, and more preferably 10% or less by mass. %, and more preferably 4% by mass. As mentioned above, the degree of pressure reduction of the azeotropic dehydration distillation column (C31) can be adjusted. A vacuum device is not required or can be made smaller, and the azeotropic dehydration distillation column (C31) can also be made smaller. The crude ethyl acrylate 1 discharged from the bottom of the azeotropic distillation column for dehydration is then The crude ethyl acrylate 2 and low boiling points 2 are separated in the boiling point separation column (C33). Since the separation of low boiling point 1 has already been carried out in the distillation column (C31), the low boiling point separation column (C33) In this case, the low boiling point material 2 can be separated efficiently. The cation exchange resin, azeotropic solvent, and polymerization inhibitor used in the present invention 2 are as described above. The same as in Invention 1 can be used. [Explanation of symbols]

[0024] C11 Dehydration distillation column C12 extraction tower C21, C31 Azeotropic dehydration distillation column C13, C33 low boiling point separation column C14, C24, C34 refinery distillation column C15, C25, C35 ethanol recovery tower V11, V21, V31 evaporators R11, R21, R31a, R31b fixed bed reactor R12, R22, R32 thermal decomposition equipment AA raw material acrylic acid EtOH raw ethanol EA Purified Ethyl Acrylate WW Wastewater

Claims

1. Acrylic acid and ethanol are supplied to a fixed-bed reactor packed with a cation exchange resin, an esterification reaction step of continuously obtaining a reaction solution by an esterification reaction, The crude ethyl acrylate is fed to an existing azeotropic dehydration distillation column and separated into crude ethyl acrylate and low boiling points. and a purification step of converting the crude ethyl acrylate into ethyl acrylate in a purification distillation column.

1. A method for producing ethyl acrylate, comprising: The azeotropic solvent is a hydrocarbon having a boiling point of 55°C to 75°C at atmospheric pressure, such as ethyl acrylate. Manufacturing method.

2. Acrylic acid and ethanol are supplied to a fixed-bed reactor packed with a cation exchange resin, an esterification reaction step of continuously obtaining a reaction solution by an esterification reaction, The crude ethyl acrylate is separated into 1 part of crude ethyl acrylate and 1 part of low boiling point material. Ethyl acrylate 1 is fed to a low boiler separation column in which an azeotropic solvent is present, and crude ethyl acrylate 2 is and a dehydration distillation step in which the crude ethyl acrylate 2 is separated into low boiling points and low boiling points. A method for producing ethyl acrylate, comprising a purification step of obtaining ethyl acrylate, The azeotropic solvent is a hydrocarbon having a boiling point of 55°C to 75°C at atmospheric pressure, and The concentration of water, ethanol and azeotropic solvent in ethyl acetate is 20% by mass or less. Method for producing ethyl acrylate.

3. 2. The method according to claim 1, wherein the low boiling point fraction is separated into an oil phase and an aqueous phase, and the oil phase is recycled to the azeotropic distillation column for dehydration. The method for producing ethyl acrylate described above.

4. 3. The method according to claim 2, wherein the low boiling point material 1 is separated into an oil phase and an aqueous phase, and the oil phase is recycled to the azeotropic distillation column for dehydration. The method for producing ethyl acrylate described above.

5. Ethanol is recovered from the aqueous phase, and the recovered ethanol is supplied to a fixed-bed reactor.

5. The method for producing ethyl acrylate according to claim 3 or 4.

6. 6. The method according to claim 1, wherein a polymerization inhibitor is used in the dehydration distillation step and / or the purification step. The method for producing ethyl acrylate according to any one of claims 1 to 10.

7. The polymerization inhibitor is a small amount selected from the group consisting of phenothiazine, copper complexes, and manganese complexes.

7. The method for producing ethyl acrylate according to claim 6, wherein the method comprises at least one of the steps of:

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