KR20100112534A - Process for production of carboxylic esters - Google Patents

Abstract

PURPOSE: A manufacturing method of carboxylic acid ester is provided to secure the industrial efficiency, and to economically manufacture the carboxylic acid ester from aliphatic carboxylic acid and aliphatic alcohol. CONSTITUTION: A manufacturing method of carboxylic acid ester reacting aliphatic carboxylic acid and aliphatic alcohol, under the presence of a catalyst comprises the following steps: reacing the aliphatic carboxylic acid and the aliphatic alcohol inside a reactor(4); supplying the outcome to a distillation column(6), and discharging water and the carboxylic acid ester while collecting the non-reactive aliphatic carboxylic acid; and recycling the non-reactive aliphatic carboxylic acid.

Description

Production method of carboxylic ester {PROCESS FOR PRODUCTION OF CARBOXYLIC ESTERS}

The present invention relates to a process for producing a corresponding carboxylic acid ester by reacting an aliphatic carboxylic acid with an aliphatic alcohol. Carboxylic acid ester is a compound useful as a raw material of a solvent, an organic synthetic product, etc.

As a manufacturing method of carboxylic acid ester, the method of making carboxylic acid and alcohol react in presence of a catalyst is known. For example, Japanese Patent Application Laid-Open No. 2001-302585 discloses a C2-C5 aliphatic carboxylic acid and a C2-C5 aliphatic alcohol continuously in the reaction zone under conditions in which the latter becomes excess than the stoichiometric reaction amount. The azeotropic mixture consisting of a three-component composition of ester / water / alcohol was distilled off by distilling the reaction crude liquid obtained by supplying in the presence of an esterification catalyst and reacting them in the presence of an esterification catalyst, followed by phase separation operation. A process for the continuous production of esters for obtaining esters is disclosed.

However, in the above method, since alcohol is excessively supplied to the reaction system, it is necessary to distill the alcohol having a lower boiling point than the ester in the distillation column together with the ester as the target product in the process of purifying the obtained ester and distillate it from the top of the column. Moreover, not only it is necessary to distill off alcohol from the obtained effluent further, but since water is distilled by adding water to the reaction crude liquid, the amount of energy required for distillation is very large.

Japanese Patent Laid-Open No. 2001-302585

It is therefore an object of the present invention to provide a method for producing a corresponding carboxylic acid ester at low cost and industrially good efficiency from aliphatic carboxylic acid and aliphatic alcohol.

Another object of the present invention is to provide a method for producing a carboxylic acid ester with a small amount of energy.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the said objective, the present inventors supplied the reaction liquid of aliphatic carboxylic acid and an aliphatic alcohol to a distillation column, and the carboxylic acid ester produced by the tower top and by-product water are distilled off, By recovering unreacted aliphatic carboxylic acid at and recycling the recovered aliphatic carboxylic acid to the reactor, the inventors found that carboxylic acid esters can be produced with industrially good efficiency, thereby completing the present invention.

That is, the present invention is a method for producing a corresponding carboxylic acid ester by reacting an aliphatic carboxylic acid and an aliphatic alcohol in the presence of a catalyst, wherein the aliphatic carboxylic acid and the aliphatic alcohol are reacted in a reactor. The reaction solution is supplied to a distillation column, the carboxylic acid ester produced by the column top and the by-product water are distilled off, and the process B which collect | recovers the unreacted aliphatic carboxylic acid from the tower bottom, and the unreacted aliphatic collect | recovered in said process B is carried out. Process C of recycling carboxylic acid to said process A is provided, The manufacturing method of the carboxylic acid ester is provided.

In this production method, it is preferable to supply the aliphatic carboxylic acid and the aliphatic alcohol to the reactor under the condition that the electrons are excessive in step A.

This production method may further include a step D for treating at least a portion of the stream flowing out of the top of the distillation column in step B with an aqueous alkali solution to neutralize the trace acid content.

According to the production method of the present invention, a reaction solution obtained by reacting an aliphatic carboxylic acid and an aliphatic alcohol in the presence of a catalyst is supplied to a distillation column, the carboxylic acid ester produced in the column top and by-product water are distilled off, Since the aliphatic carboxylic acid of reaction is collect | recovered and it is recycled to a reaction process, the utilization rate of aliphatic carboxylic acid can be raised. In addition, since a strong acid catalyst is usually used as a catalyst, the strong acid catalyst can be recovered together with the unreacted aliphatic carboxylic acid at the bottom of the column and can be recycled to the reaction step, so that the catalyst can be effectively used. In addition, since it is possible to remove the strong acid catalyst at an early stage of the process, it is possible to prevent the decomposition of the target compound based on the shift of the equilibrium state by the strong acid catalyst in the subsequent step, and the progress of side reactions using the strong acid as a catalyst. In addition, the need for equipment using high-quality materials with high durability in subsequent processes can be avoided, thereby avoiding additional investment due to reduced initial investment or equipment renewal. In addition, by using an excess amount of aliphatic carboxylic acid with respect to an aliphatic alcohol, it is not necessary to make a large amount of alcohol flow out with the said carboxylic acid ester in the refinement | purification process of the produced | generated carboxylic acid ester, and also distilling, adding water. It is not necessary to do this, and since the carboxylic acid ester and water can be easily separated by separating the effluent, the amount of energy used can be greatly reduced. In addition, since the aliphatic carboxylic acid used in excess is recovered at the bottom of the distillation column and recycled to the reaction step, the energy required for recovery is very small. Therefore, according to the present invention, the carboxylic acid ester can be produced at low cost and industrially good efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic flowchart which shows an example of the manufacturing method of the carboxylic acid ester of this invention.

In the present invention, the corresponding carboxylic acid ester is produced by reacting an aliphatic carboxylic acid and an aliphatic alcohol in the presence of a catalyst.

As aliphatic carboxylic acid used as a raw material, For example, C2-C5 saturated aliphatic carboxylic acids, such as an acetic acid, propionic acid, butanoic acid; C2-C5 unsaturated aliphatic carboxylic acid, such as acrylic acid and methacrylic acid, etc. are mentioned. Aliphatic carboxylic acid can be used individually or in combination of 2 or more types. On the other hand, as an aliphatic alcohol used as a raw material, C2-C5 aliphatic alcohols, such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, amyl alcohol, etc. are mentioned. Aliphatic alcohol can be used individually or in combination of 2 or more types. The preferable combination of aliphatic carboxylic acid and aliphatic alcohol is a combination in which the boiling point of the carboxylic acid ester produced becomes lower than the boiling point of the aliphatic carboxylic acid of a raw material. More specifically, for example, a combination of acetic acid and ethanol, n-propyl alcohol or isopropyl alcohol is preferable, and a combination of acetic acid and ethanol is particularly preferable. Moreover, this invention has a big effect when the boiling point of aliphatic alcohol is lower than the boiling point of aliphatic carboxylic acid.

When impurities (particularly low boiling point components) are contained in the aliphatic carboxylic acid and aliphatic alcohol used as raw materials, a considerable amount of carbol is removed when the impurities or by-products resulting from the impurities are separated and removed in the purification process of the carboxylic acid ester. Acid esters are lost. Therefore, in order to reduce the loss of these target objects, when many impurities are contained in the aliphatic carboxylic acid and aliphatic alcohol used as a raw material, it is preferable to refine | purify by distillation or other purification means before providing to reaction. In addition, as aliphatic carboxylic acid and aliphatic alcohol used as a raw material, the aliphatic carboxylic acid and aliphatic alcohol collect | recovered by the following refinement | purification process can also be used for circulation.

In process A of this invention, the said aliphatic carboxylic acid and aliphatic alcohol are supplied to a reactor and made to react. The reactor is not particularly limited, and may be any one of a stirred tank reactor, a tower reactor, a packed column reactor (for example, a reactor filled with an ion exchange resin) and the like. Although the supply ratio of an aliphatic carboxylic acid and an aliphatic alcohol is not specifically limited, It is preferable to supply to an reactor on condition that an aliphatic carboxylic acid becomes excess with respect to an aliphatic alcohol. By using an aliphatic carboxylic acid excessively with respect to an aliphatic alcohol in this way, it is not necessary to drain a large amount of unreacted alcohol in the distillation process of a subsequent carboxylic acid ester, and energy usage can be reduced. In addition, since excess aliphatic carboxylic acid is recovered at the bottom of the column in the next distillation process and is recycled to the reactor, it is not necessary to use much energy. In step A, the feed ratio (molar ratio) of the aliphatic carboxylic acid and the aliphatic alcohol to the reactor is preferably an excess of the former (e.g., the former is 1.2 times or more, preferably 1.8 times or more). Preferably the former: latter (molar ratio) = 1.8 to 4.0: 1, more preferably the former: latter (molar ratio) = 2.0 to 3.5: 1.

As the catalyst, a known esterification catalyst can be used. As esterification catalyst, For example, inorganic acids, such as a sulfuric acid; Sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid (PTS), p-octylbenzenesulfonic acid (OBSA), dodecylbenzenesulfonic acid (DBSA), naphthalenesulfonic acid, methanesulfonic acid (MSA), ethanesulfonic acid and trifluoromethanesulfonic acid; Salts of these acids with organic bases (for example, pyridinium p-toluenesulfonic acid (PPTS), etc.); Strongly acidic ion exchange resins; Magnesium chloride, aluminum chloride, titanium tetrachloride; Solid acid catalysts; Among these, p-toluenesulfonic acid (PTS), sulfuric acid, and a strong acidic ion exchange resin are preferable, and p-toluenesulfonic acid (PTS) and a strongly acidic ion exchange resin are especially preferable.

Although the usage-amount of a catalyst changes also with the kind, it is 0.01-5 weight%, Preferably it is about 0.05-2 weight% with respect to the total amount of the aliphatic carboxylic acid and aliphatic alcohol supplied to a reactor.

Reaction conditions other than the said feed ratio in process A can employ | adopt the usual general conditions in esterification reaction. For example, the reaction temperature also varies depending on the raw materials, but is generally 60 to 140 ° C, preferably 70 to 100 ° C, more preferably 65 to 95 ° C. The reaction may be any one of a reduced pressure, a normal pressure, and a pressurized pressure, but a normal pressure is preferable from the viewpoint of operability. The reaction time (retention time in the reactor) is usually about 3 to 120 minutes (for example, 3 to 30 minutes).

In the present invention, most reactions are carried out in step A, and the remaining reactions are carried out in step B. In step A, the reaction may be terminated completely. The conversion rate of the aliphatic alcohol in the step A is usually 70 to 100%, preferably 80 to 100% (for example, 80 to 90%).

In the process B of this invention, the reaction liquid obtained at the process A is supplied to a distillation column, the carboxylic acid ester produced | generated in the tower top, and the by-product water are distilled off, and unreacted aliphatic carboxylic acid is collect | recovered from a tower bottom. When the catalyst is dissolved or dispersed in the reaction liquid, the catalyst is also supplied to the distillation column, so that the reaction proceeds further in the distillation column. When the catalyst is an ion exchange resin or a solid acid catalyst and is used in the form filled in the reactor, the catalyst is not supplied to the distillation column, but the acid partially liberated from the catalyst may be supplied to the distillation column. As described above, when the reaction is carried out even in a distillation column, the reaction is carried out while distilling off the water by-produced in the reaction, so that the equilibrium of the reaction is inclined to the product side, and the reaction proceeds efficiently and the crude acid value is low. Carboxylic acid ester is obtained. In addition, when an excessive amount of aliphatic carboxylic acid is used, since the amount of unreacted aliphatic alcohol is small, not only can the energy consumed in order to drain the alcohol to be greatly reduced, but also water must be added as in the prior art. Since there is no, the amount of energy can be reduced.

Reaction in the distillation column in process B (when a catalyst is supplied to a distillation column) is performed in the area | region (reaction zone) in which the catalyst lower than the supply position of the reaction liquid obtained in process A exists. Aliphatic carboxylic acid (which may be a cyclic aliphatic carboxylic acid to be used) and aliphatic alcohol (which may be a cyclic aliphatic alcohol to be used) of a raw material can also be supplied to this reaction zone, respectively. In particular, when the aliphatic alcohol is supplied to the reaction zone of the distillation column, the reaction efficiency is improved. In this case, the amount of aliphatic alcohol supplied to the reaction zone of the distillation column is about 10 to 30 parts by weight based on 100 parts by weight of the reaction liquid supply amount to the distillation column. Moreover, an evaporation can can be installed in a distillation column, the reaction liquid obtained at the process A can be supplied to this evaporation can, and the vapor obtained can be put into a distillation column. In this case, the evaporation can serves as the bottom of the distillation column and becomes a reaction zone (when a catalyst is supplied to the distillation column). The liquid at the bottom of the distillation column is returned to the evaporation can, and unreacted aliphatic carboxylic acid (usually including a catalyst when the catalyst is supplied to the distillation column) is recovered from the evaporation can.

The conversion ratio of the aliphatic alcohol which passed process A and process B is 75 to 100% normally, Preferably it is 80 to 100%. Unreacted aliphatic carboxylic acid is recovered at the bottom of the distillation column. In this invention, although this collect | recovered aliphatic carboxylic acid is recycled to a reactor, the process of recycling a part of collect | recovered aliphatic carboxylic acid as it is or appropriately and recycling to the reaction zone of the distillation column in process B can also be provided.

The kind of distillation column in the process B is not specifically limited, Any of a packed column, a shelf tower, a seed tower, etc. may be sufficient. The stage of the distillation column is, for example, 10 to 100 stages of theoretical stages, preferably 20 to 60 stages of theoretical stages, and the pressure during distillation is usually atmospheric pressure, but may be distilled under reduced pressure or pressure. The reflux ratio can be appropriately selected in consideration of the separation efficiency (mainly the separation efficiency of the carboxylic acid ester and the unreacted aliphatic carboxylic acid), the separation of the effluent, the energy cost, and the like.

In step C of the present invention, the unreacted aliphatic carboxylic acid recovered in step B is recycled to step A. The unreacted aliphatic carboxylic acid recovered usually contains a catalyst (in addition, when the catalyst is an ion exchange resin or a solid acid catalyst and is used in a form filled in the reactor, the catalyst is not usually included). . The recovered unreacted aliphatic carboxylic acid may be usually recycled to step A together with the catalyst, or may be appropriately purified and recycled to step A.

Although the flow (effluent) which flowed out from the top of a distillation column in the process B may be a single layer depending on conditions, it divides into two layers in many cases. In particular, when an excessive amount of aliphatic carboxylic acid is used during the reaction, since the amount of unreacted aliphatic alcohol that is easily dissolved in water in distillation is very small, the distillation column of the distillation column usually contains the produced carboxylic acid ester as a main component. It separates easily with the water layer which has an organic layer and by-product water as a main component. Therefore, it becomes possible to collect | recover carboxylic acid ester efficiently from this organic layer.

A small amount of acid content may be contained in the flow (effluent) which flowed out from the top of a distillation column in the said process B. For this reason, the process D which neutralizes the said trace amount of acid content can be provided by processing the organic layer (carboxylic acid ester layer) obtained by separating at least one part of the flow which flowed out from the top of a distillation column, Preferably the flow which flowed out by aqueous alkali solution. have. By providing this step D, the decomposition of the target compound based on the shift of the equilibrium state by the strong acid catalyst in the subsequent step and the progress of the side reaction using the strong acid as a catalyst can be more reliably prevented, Since the equipment using the durable high quality material is completely unnecessary, the equipment cost can be greatly reduced.

As aqueous alkali solution used for the said neutralization, For example, aqueous solution of alkali metal hydroxides, such as sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; Aqueous solutions of alkali metal carbonates such as sodium carbonate aqueous solution; Aqueous solutions of alkali metal hydrogencarbonates such as aqueous sodium bicarbonate solution; The aqueous solution of alkaline-earth metal hydroxides, such as magnesium hydroxide aqueous solution, etc. are mentioned. Among these, aqueous solutions of alkali metal hydroxides, such as sodium hydroxide aqueous solution, are preferable.

The alkali concentration in the aqueous alkali solution is, for example, 1 to 40% by weight, preferably 2 to 30% by weight, more preferably about 5 to 20% by weight.

The treatment with the aqueous alkali solution may be performed a plurality of times. It is preferable to repeat until a pH of a water layer becomes seven or more after a process. In addition, it is preferable to perform processing by aqueous alkali solution until the acid content (conversion of acetic acid) in an organic layer (carboxylic acid ester layer) after a process becomes 0.01 weight% or less, especially 0.001 weight% or less, for example.

After the treatment with an aqueous alkali solution, water washing may be performed as necessary.

The crude carboxylic acid ester thus obtained is further commercialized after passing through conventional purification means. As said purification means, the refinement | purification by a distillation column (rectification tower), etc. are mentioned, for example. The distillation column is not particularly limited, and may be any of a packed column, a bandung tower, a seed tower, and the like. The stage of the distillation column is, for example, 5 to 100 stages of theoretical stages, preferably 10 to 80 stages of theoretical stages, and the pressure during distillation is usually atmospheric pressure, but may be distilled under reduced pressure or pressure. This refining process may be constituted by a de-low boiling step of separating and removing the low boiling point component and a de-high boiling step of separating and removing the high boiling point component, and in one distillation column, as one step of separating the low boiling point and high boiling point components at the same time. It can also be configured.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic flowchart which shows an example of the manufacturing method of the carboxylic acid ester of this invention. In this example, ethyl acetate is prepared from acetic acid and ethanol. Carboxylic acid esters other than ethyl acetate can be manufactured basically according to this example, but may be appropriately changed depending on the physical properties (boiling point, solubility in water, etc.) of the raw materials and the product. Hereinafter, the flowchart of FIG. 1 is demonstrated.

Reactor 4 is reacted by continuously feeding feedstock acetic acid from line 2, feedstock ethanol from line 1, and catalyst solution (supplementary; if necessary) from line 3, respectively. The catalyst solution (supplementary) can also be supplied to the distillation column effluent line (8). The reaction liquid is continuously supplied to the distillation column 6 through the line 5, and when the catalyst is supplied to the distillation column, the reaction liquid is produced in the reaction through the line 7 at the top of the column while further progressing the reaction in the distillation column 6. The by-product water is distilled off from the reaction with the prepared ethyl acetate. The effluent is separated in a decanter 9, a portion of the upper layer (organic layer; ethyl acetate as the main component) is refluxed to the distillation column 6, and the remainder is supplied to the neutralization tank 14 through line 11. The aqueous alkali solution is supplied to the neutralization tank 14 through the line 13, and it stirs and mixes with the upper layer (organic layer) of the said decanter 9, and transfers the trace acid contained in the upper layer to a water layer. The mixed liquid is supplied to the decanter 16 via the line 15, and is separated into an upper layer (ethyl acetate as a main component) and a lower layer (water is a main component and contains a small amount of ethanol) by standing. The upper layer (organic layer) of the decanter 16 is fed to the reaction crude liquid tank 19 via line 18 and further provided to a purification process to obtain a product of ethyl acetate.

The effluent of the distillation column 6 (unreacted acetic acid and catalyst, if included) is recycled to reactor 4 via line 8. On the other hand, the lower layer (aqueous layer) of the decanter 9 and the lower layer (aqueous layer) of the decanter 16 are supplied to the alcohol recovery system via the line 12, the line 17 and the line 20, respectively, and ethanol is recovered. . Some or all of the recovered ethanol is recycled to reactor 4 via line 21.

<Examples>

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this.

Ethyl acetate was manufactured according to the flow shown in FIG.

The feed rate ratio (molar ratio) in the starting material was ethanol: acetic acid = 1.0: 2.2, the concentration in the starting material of the esterification catalyst (sulfuric acid): 0.7 to 1.7% by weight, reaction temperature in the reactor (4): 70 to 80 ° C, reaction Pressure: normal pressure, reaction time: The preliminary reaction in reactor 4 was performed on condition of about 5 minutes. The obtained reaction liquid was poured into the distillation column 6 (single stage: 60 stages), azeotroped the produced ethyl acetate and the by-product water, and the condensate distillate was separated by the decanter 9, and all the lower layer liquid was passed to the alcohol recovery system. The supernatant was fed to some distillation column (6), and the rest was fed to the neutralization tank (14). The can temperature of the distillation column 6 was 120 degreeC, the column top pressure of the distillation column 6 was atmospheric pressure, and the liquid flow time in the distillation column 6 was about 1 hour.

The composition (component ratio; molar ratio) of the supernatant of the decanter 9 was ethanol: acetic acid: water: ethyl acetate = 0.12: 0.005: 0.28: 0.6. In addition, the composition (component ratio; molar ratio) of the effluent of the distillation column 6 was ethanol: acetic acid: water: ethyl acetate = 0: 0.998: 0.002: 0. The composition (component ratio; molar ratio) of the lower layer liquid of the decanter 9 was ethanol: acetic acid: water: ethyl acetate = 0.66: 0.001: 0.92: 0.02. In addition, the weight ratio of the supernatant liquid of the decanter 9 supplied to the neutralization tank 14, the effluent liquid of the distillation column 6, and the lower layer liquid of the decanter 9 was 3: 3: 1 in this order. Regarding sulfuric acid as a catalyst, the total amount added was left in the effluent of the distillation column 6. It was recycled to reactor 4 with unreacted acetic acid. In addition, the acid content (in acetic acid conversion) of the supernatant liquid of the decanter 9 was about 0.47 weight%.

In the neutralization tank 14 to which the supernatant liquid of the said decanter 9 was supplied, 10 weight% sodium hydroxide aqueous solution was added so that pH might be 7, and neutralization removal of the acid content was performed. The same operation was further performed with respect to the supernatant obtained by the liquid separation operation in the decanter 16 so that pH might be 10-11. Then, washing and liquid separation were performed only with water. The obtained process liquid (supernatant (after water washing) of the decanter 16) was sent to the reaction tank liquid tank (19).

As a result, the acid content (in terms of acetic acid) in the process solution was 0.0001% by weight, which is a low value that does not require special consideration for the acid content in the subsequent process, and therefore, the material of the device was sufficient to use ordinary SUS material. . This process solution was then rectified in a rectifying column to obtain ethyl acetate as a product. The consistent yield in the reaction step was 98%.

Ethyl acetate was prepared according to the flowchart shown in FIG. As reactor 4, a tower reactor was used.

The feed rate ratio (molar ratio) in the starting material was ethanol: acetic acid = 1.0: 3.3, the concentration in the starting material of the esterification catalyst (paratoluenesulfonic acid: PTS): 0.7 to 1.7% by weight, reaction temperature in the reactor (4): 70 to Preliminary reaction in the reactor (4) was performed on the conditions of 80 degreeC, reaction pressure: normal pressure, and reaction time: about 10 minutes. As a result, the composition (component ratio; molar ratio) of the obtained reaction liquid was ethanol: acetic acid: water: ethyl acetate = 0.33: 2.8: 2.4: 1.0.

The obtained reaction liquid was introduced into the evaporation can of the distillation column 6 (stage number: 60 stages) provided with the evaporation can, and the steam was supplied to the distillation column 6 to azeotropically condensate the produced ethyl acetate and by-product water. The distillate is separated from the decanter 9, all of the lower layer is fed to an alcohol recovery system, the supernatant is refluxed to some distillation column 6, and the remainder is not treated with an aqueous alkali solution, but to the reaction crude liquid tank 19. It was sent. The lowest liquid of the distillation column 6 returned to the evaporation can. The can temperature of the said evaporation can was 85 degreeC, the column top pressure of the distillation column 6 was atmospheric pressure, and the liquid residence time in a distillation column was about 1 hour. In addition, about PTS which is a catalyst, the total amount thrown in through the evaporating can leach liquid remained in the reaction liquid. The effluent of the evaporation can was recycled to the reactor (4).

As a result, the obtained process liquid [supernatant liquid of the decanter 9; The acid content (in terms of acetic acid) in the liquid of the reaction crude liquid tank 19 becomes 0.0003% by weight, and since it is a low value that does not require special consideration for the acid content in a subsequent step, the material of the device is made of a conventional SUS material. It was enough to use. This process liquid was then rectified with a rectifying column, and ethyl acetate as a product was obtained. The consistent yield in the reaction step was 99.5%.

Ethyl acetate was manufactured according to the flowchart shown in FIG. This example is also an ethanol excess system.

The feed rate ratio (molar ratio) in the starting material was ethanol: acetic acid = 2.2: 1.0, the concentration in the starting material of the esterification catalyst (sulfuric acid): 0.7 to 1.7% by weight, reaction temperature in the reactor (4): 70 to 80 ° C, reaction Preliminary reaction in the reactor (4) was performed on the conditions of pressure: normal pressure and reaction time: about 10 minutes. The obtained reaction liquid was thrown into the distillation column 6 (number of stages: 60 stages), the azeotrope produced water and a by-product water were azeotropic, and the condensate effluent was guide | induced to the decanter 9. The effluent contained much ethanol and was not separated from the decanter 9. A part of the effluent was refluxed to the distillation column 6 and the remainder was supplied to the neutralization tank 14. The can temperature of the distillation column 6 was 120 degreeC, the column top pressure of the distillation column 6 was atmospheric pressure, and the liquid flow time in the distillation column 6 was about 1 hour.

As a result, the liquid composition (component ratio; molar ratio) of the decanter 9 was ethanol: acetic acid: water: ethyl acetate = 0.56: 0.01: 0.07: 0.36. The composition (component ratio; molar ratio) of the effluent of the distillation column 6 was ethanol: acetic acid: water: ethyl acetate = 0: 0.97: 0.03: 0. In addition, the weight ratio of the liquid (distillation tower effluent) of the decanter 9 supplied to the neutralization tank 14, and the effluent of the distillation tower 6 was 4: 1 in this order. The effluent of the distillation column 6 was recycled to the reactor 4.

In the neutralization tank 14 to which the liquid (distillation column effluent) of the said decanter 9 was supplied, 10 weight% sodium hydroxide aqueous solution was added so that pH might be 7, and neutralization of acid content was performed. The same operation was further performed with respect to the supernatant liquid obtained by the liquid separation operation in the decanter 16 so that pH might be 10-11. Then, washing and liquid separation were performed only with water. The obtained process liquid (supernatant (after water washing) of the decanter 16) was sent to the reaction tank liquid tank (19).

As a result, the acid content (in terms of acetic acid) in the process solution was 0.0001% by weight, which is a low value that does not require special consideration for the acid content in the subsequent process, and therefore, the material of the device was sufficient to use ordinary SUS material. . This process solution was then rectified in a rectifying column to obtain ethyl acetate as a product. The consistent yield in the reaction step was 96%.

In comparison with Example 1, in Example 3, the amount of unreacted ethanol in the reaction crude liquid containing the same amount of the target compound as Example 1 is 9 times, and the energy required for the recovery of purification of this ethanol Is big.

As mentioned above, it turns out that Example 1 does not act as a catalyst of an opposite reaction compared with Example 3, and the fall of the yield of a target compound can be prevented. In addition, the amount of energy required for recovery of unreacted raw materials is also small.

Ethyl acetate was prepared according to the flowchart shown in FIG. As reactor 4, a packed tower (resin tower) reactor filled with a strongly acidic ion exchange resin was used.

The feed time ratio (molar ratio) in the starting material was ethanol: acetic acid: water: ethyl acetate = 1.0: 3.6: 1.8: 0.32, and the residence time of the process in the resin column packed with an esterification catalyst (strongly acidic ion exchange resin: IER): about 10 Reaction in reactor (4) was performed on the conditions of minutes and reaction temperature: 60 degreeC, and reaction pressure: normal pressure. As a result, the composition (component ratio; molar ratio) of the obtained reaction liquid was ethanol: acetic acid: water: ethyl acetate = 0.047: 0.44: 0.36: 0.15.

The obtained reaction liquid was thrown into the distillation column 6 (number of stages: 60 stages), azeotroped the produced ethyl acetate and the by-product water, the liquid condensate was separated in the decanter 9, and the lower layer liquid was supplied to the alcohol recovery system, The supernatant liquid was refluxed in a part of the distillation column 6, and the remainder was fed to the reaction crude liquid tank 19 without being treated with an aqueous alkali solution. The effluent of the distillation column 6 was cooled and returned to the reactor 4.

As a result, the obtained process liquid [supernatant liquid of the decanter 9; The acid content (in terms of acetic acid) in the liquid of the reaction crude liquid tank 19 becomes 0.0003% by weight, which is a low value that does not require special consideration for the acid content in the subsequent process, so that the material of the apparatus is made of a conventional SUS material. Was enough. This process solution was then rectified in a rectifying column to obtain ethyl acetate as a product. The consistent yield in the reaction step was 99%.

1: raw alcohol supply line
2: raw carboxylic acid supply line
3: catalyst solution supply (supplement) line
4: reactor
5: reaction liquid line
6: distillation column
7: distillation column outlet line
8: distillation column effluent line
9: decanter
10: Decanter Supernatant Reflux Line
11: Decanter Supernatant Line
12: Decanter Subsurface Line
13: alkali aqueous solution supply line
14: China
15: Mixed solution line
16: decanter
17: Decanter Subsurface Line
18: Decanter Supernatant Line
19: reaction tank
20: recovery meter supply line
21: recovery alcohol line

Claims (3)

A method for producing a corresponding carboxylic acid ester by reacting an aliphatic carboxylic acid and an aliphatic alcohol in the presence of a catalyst, wherein the reaction liquid obtained in the step A and the reaction A in which the aliphatic carboxylic acid and the aliphatic alcohol are reacted in a reactor is added to a distillation column. Supply B, the carboxylic acid ester produced | generated in the tower top, and the by-product water are made to flow out, Process B which collect | recovers unreacted aliphatic carboxylic acid from a tower bottom, and Unreacted aliphatic carboxylic acid collect | recovered in said process B are mentioned above. The process C of recycling to process A is included, The manufacturing method of the carboxylic acid ester characterized by the above-mentioned. The method for producing a carboxylic acid ester according to claim 1, wherein in step A, aliphatic carboxylic acid and aliphatic alcohol are supplied to the reactor under conditions in which electrons are excessive. The method for producing a carboxylic acid ester according to claim 1 or 2, further comprising a step D of treating at least a part of the stream flowing out of the top of the distillation column in step B with an aqueous alkali solution to neutralize the trace acid content.

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