CN118373739A - Method and device for synthesizing dimethyl succinate by continuously applying fractions - Google Patents

Abstract

The invention relates to a method and a device for synthesizing dimethyl succinate by continuously applying fractions, wherein the method comprises the steps of taking succinic acid, methanol and a catalyst as raw materials, and performing a monoesterification reaction to generate monomethyl succinate to obtain a reaction solution A; distilling the reaction solution A under reduced pressure, adding methanol after the distillation is completed, and performing secondary esterification reaction to generate dimethyl succinate; repeating the esterification reaction for at least one time until the content of monomethyl succinate in the reaction system is less than or equal to 1%, so as to obtain a reaction solution B; carrying out reduced pressure distillation on the reaction liquid B twice, and separating to obtain a dimethyl succinate product, kettle residues and methanol with water; and (3) mechanically applying the residue and part of the water-carrying methanol to a single esterification reaction, and mechanically applying the rest of the water-carrying methanol to a secondary esterification reaction. The synthesis method is simple, low in energy consumption, low in dosage of methanol and catalyst, free of separate separation of methyl succinate, suitable for continuous industrial production and high in economic benefit.

Description

Method and device for synthesizing dimethyl succinate by continuously applying fractions

Technical Field

The application relates to the technical field of pharmaceutical chemicals, in particular to a method and a device for synthesizing dimethyl succinate by continuously applying fractions.

Background

Dimethyl succinate (also called dimethyl succinate) is an important synthetic spice and food additive, can be used as an edible preservative, is also an important chemical intermediate, and is widely applied to the preparation of various chemicals. The traditional production method is to take succinic acid and methanol as raw materials and concentrated sulfuric acid as a catalyst to obtain the catalyst through esterification reaction, the process has the advantages of multiple side reactions, complex post-treatment, serious equipment corrosion, and serious environmental pollution, and the byproduct is highly toxic dimethyl sulfate. Then, in order to avoid the problem of the traditional production mode, some enterprises use maleic anhydride and methanol as raw materials, and use metal oxide as a catalyst to catalyze and generate dimethyl maleate, and then the dimethyl succinate is produced by catalytic hydrogenation. The method has low quality and long route, obviously increases the production cost and seriously hinders the economy of the dimethyl succinate product.

In order to solve the problems, the prior researches provide continuous catalytic rectification for synthesizing dimethyl succinate, which takes succinic acid and methanol as raw materials and takes self-developed temperature-resistant cation exchange resin as a catalyst, and adopts a catalyst-free continuous pre-esterification and continuous catalytic rectification synthesis process for synthesizing the dimethyl succinate. Specifically, methanol and succinic acid are added into a pre-esterification reactor according to a certain proportion, and an autocatalysis reaction is carried out under a certain condition to generate succinic acid monovalent ester. The pre-esterification reaction product enters the upper part of the catalytic rectifying tower to be in countercurrent contact with formaldehyde steam rising from the bottom of the rectifying tower from top to bottom, so that the succinic acid monovalent ester in the reaction product is gradually converted into dimethyl succinate. However, the method uses large amount of methanol, has high methanol ratio and high energy consumption.

The patent with publication number CN113461523A provides a preparation method and equipment of dimethyl succinate, wherein maleic anhydride and methanol are used as raw materials as substrates, dimethyl maleate is obtained through catalytic reaction in a reaction kettle, and dimethyl succinate is obtained through distillation after catalytic hydrogenation. The method needs hydrogenation in reaction, has high equipment requirement, poor safety and low product yield and quality.

The patent with publication number CN105367416A provides a method for preparing dimethyl succinate, wherein succinic acid and methanol are used as raw materials of a substrate, a dehydrating agent is added, a supported solid acid catalyst is used for catalyzing and generating monomethyl succinate, and then the monomethyl succinate is separated and dehydrated to generate dimethyl succinate. The process uses a large amount of dehydrating agents, so that the problems of high energy consumption, high separation difficulty of the succinic acid monovalent ester, high methanol consumption, low yield and complex operation are caused.

The patent with publication number CN106800510A provides a production method of dimethyl succinate, the substrate is prepared from succinic acid and methanol, potassium hydrogen sulfate monohydrate is used as a catalyst, esterification is carried out under the pressure of 0.2MPa, and dimethyl succinate is obtained by filtering, distilling methanol and water and then rectifying. The process is provided with pressure equipment, the requirement is high, the catalyst consumption is extremely large, the activation method is complex, and the methanol consumption is large.

The production method of the dimethyl succinate has the problems of high methanol ratio and large catalyst consumption, and the monomethyl ester is difficult to separate, so that the process flow is complicated, the equipment requirement is high, the energy consumption is high, and the actual production economy is not high.

In sum, if the synthesis method of the dimethyl succinate can be provided, the process is simple, the raw material utilization rate is high, and the energy consumption is low, so that the method is more beneficial to improving the practical production economy.

Disclosure of Invention

In view of the shortcomings of the prior art, the invention provides a method and a device for synthesizing dimethyl succinate by continuously applying fractions, which are used for solving the problems of complex preparation process, large methanol consumption, high recovery energy consumption, difficult separation of monomethyl succinate, low economic benefit and the like of the existing high-purity dimethyl succinate.

In order to achieve the above and related objects, the present invention adopts the following technical scheme:

A method for synthesizing dimethyl succinate by continuously applying fractions, comprising the following steps:

(1) Taking succinic acid, methanol and a catalyst as raw materials, and performing a single esterification reaction to generate monomethyl succinate to obtain a reaction solution A;

(2) Distilling the reaction solution A under reduced pressure, separating methanol from water to obtain a reaction system, adding methanol after the distillation is completed, and performing secondary esterification reaction to generate dimethyl succinate;

(3) Repeating the step (2) at least once until the content of monomethyl succinate in the reaction system is less than or equal to 1%, so as to obtain a reaction solution B;

(4) Carrying out reduced pressure distillation on the reaction liquid B, separating methanol from water to obtain a reaction system, and obtaining a dimethyl succinate crude product; distilling the crude product of dimethyl succinate under reduced pressure, and separating to obtain a dimethyl succinate product, kettle residues and methanol with water;

(5) And (3) applying the residue in the step (4) and part of the water-carrying methanol to the step (1), and applying the rest of the water-carrying methanol to the step (2).

In an embodiment of the present application, the method further includes recovering the fraction distilled in the step (2), rectifying the fraction, sequentially rectifying methanol and water, applying the rectified residual liquid to the step (1), and applying the distilled methanol to one or more steps of the step (1), the step (2) and the step (3).

In one embodiment of the present application, the molar ratio of succinic acid to methanol in step (1) is 1: (2-3).

In one embodiment of the present application, the molar ratio of monomethyl succinate to additional methanol in step (2) is 1: (2-3).

In one embodiment of the present application, the molar ratio of monomethyl succinate to additional methanol in step (3) is 1: (5-6).

In one embodiment of the present application, the catalyst in the step (1) is an acidic cation exchange resin, a sulfate esterification catalyst or p-toluenesulfonic acid.

In one embodiment of the present application, the reaction conditions of step (1) are selected from at least one of the following (i) to (iii):

Heating temperature is 68-95 ℃;

(II) reflux reaction is carried out for 2 to 3.5 hours;

(III) the catalyst is used in an amount of 0.5 to 3% based on the total mass of succinic acid and methanol in the step (1).

In one embodiment of the present application, the reaction conditions of step (2) are selected from at least one of the following (i) to (ii):

vacuum degree of reduced pressure distillation is 20-60 mmHg;

(II) after adding methanol, reflux reaction is carried out for 1.5h to 2.5h at the temperature of 68 ℃ to 95 ℃.

In one embodiment of the present application, the source of additional methanol is one or more of fresh methanol, distilled methanol, and aqueous methanol separated in step (4).

A device for synthesizing dimethyl succinate by continuously applying fractions comprises a first-stage reaction system, a second-stage reaction system, a third-stage reaction system and a refining system which are sequentially arranged along a reaction direction, wherein the first-stage reaction system is a place where succinic acid and methanol are subjected to a single esterification reaction, moisture in the reaction system is removed, and a second esterification reaction is performed to generate dimethyl succinate; the secondary reaction system is a place for repeatedly carrying out secondary esterification reaction, removing water in the reaction system and reducing the content of monomethyl succinate in the reaction system; the third-stage reaction system separates methanol and water from the reaction system through reduced pressure distillation to prepare a dimethyl succinate crude product, and the distilled fraction is applied to the sites of the first-stage reaction system and the second-stage reaction system; the refining system is used for refining the crude product of the dimethyl succinate by reduced pressure distillation, and the refined crude product is applied to the place where the residue is left in the first-stage reaction system.

The beneficial technical effects of the invention are as follows:

(1) The method comprises the steps of taking succinic acid as a raw material to synthesize dimethyl succinate, performing two-step reaction, completing single esterification of succinic acid and methanol to generate monomethyl succinate, and performing secondary esterification of the monomethyl succinate and the methanol to generate dimethyl succinate. The esterification reaction is a reversible equilibrium reaction, the reaction system is separated from water by repeated reduced pressure distillation, and the balance of the reversible reaction is forced to shift rightwards, so that the dosage of methanol is reduced, and single methyl succinate is not required to be separated independently, thereby improving the yield of dimethyl succinate products.

(2) In the process of secondary esterification reaction and repeated secondary esterification reaction, methanol and water are separated from a reaction system, so that the moisture content in the reaction system is reduced, distilled fractions are rectified, methanol and water are sequentially rectified, and rectified residual liquid is repeatedly used as a supplementary raw material to continuously synthesize dimethyl succinate; the rectified methanol is recycled and used as a raw material methanol and a supplemental methanol source, so that the consumption of fresh methanol is reduced, and the rectified methanol does not contain water, and the water content of a reaction system is not increased when the rectified methanol is applied to repeated secondary esterification reaction. Meanwhile, the kettle residue and part of the water-carrying methanol separated by reduced pressure distillation are applied to the monoesterification reaction, and the rest of the water-carrying methanol is applied to the secondary esterification reaction to be used as a supplementary raw material and a supplementary methanol source so as to reduce the dosage of fresh methanol. In addition, water is continuously separated in the multi-step esterification reaction process, so that the water content in the methanol with water is low, the water can be directly reused without being separated again. The application continuously recycles the methanol separated in the synthesis process, realizes the recycling of the methanol, and improves the utilization rate of raw materials, thereby reducing the consumption of fresh methanol and improving the practical economy.

(3) The application has the advantages of less methanol consumption, less methanol to be recovered after rectification and low energy consumption.

(4) The catalyst has small dosage, multiple types of optional catalysts, the conventional esterification catalyst and the novel solid acid catalyst can achieve the same reaction effect, the catalyst can be repeatedly used, and the production cost is reduced.

(5) The synthesis method is simple, is easy to realize industrially, and can be used for continuously synthesizing the dimethyl succinate; the catalyst is easy to obtain, and can avoid the catalyst with stronger corrosion to equipment, thereby reducing the corrosion to the equipment; the normal pressure reaction of the application has low equipment requirement, less waste and high economical efficiency.

(6) The dimethyl succinate synthesized by the synthesis method and the synthesis device has the advantages of high yield, high purity and low moisture content.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a method for synthesizing dimethyl succinate by continuously applying fractions according to the application;

FIG. 2 is a schematic diagram of an apparatus for synthesizing dimethyl succinate using a continuous cut according to the present application.

Reference numerals

R101: a first-stage reaction kettle; e101: a first distillation condenser; t101: a first reduced pressure distillation column; v101: a first fraction collection tank; p101: a first transfer pump; r102: a second-stage reaction kettle; e102: a second distillation condenser; t102: a second reduced pressure distillation column; v102: a second fraction collection tank; p102: a second transfer pump; r103: a third-stage reaction kettle; e103: a third distillation condenser; t102: a third reduced pressure distillation column; v103: a third fraction collection tank; p103: a third transfer pump; e104: a recovery condenser; t104: a methanol recovery column; v104: a methanol temporary storage tank; p104: a fourth transfer pump; e105: a product condenser; t105: a product distillation column; v105: a product collection tank; p105: a fifth transfer pump; p106: a product distillation vacuum pump; p107: and a distillation vacuum pump.

Detailed Description

Unless defined otherwise, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or in any other described embodiment of the invention as appropriate. Certain features described in the context of various embodiments will not be considered essential features of those embodiments unless the embodiments are not operable without those elements. The present invention will be further described with reference to the following specific examples, but it should be understood that the specific process conditions, results, etc. described in the examples of the present invention are only for illustrating the present invention, and are not intended to limit the scope of the present invention, and all equivalent changes or modifications according to the spirit of the present invention should be included in the scope of the present invention.

The invention provides a method for synthesizing dimethyl succinate by continuously applying fractions, which comprises the following steps:

(1) Taking succinic acid, methanol and a catalyst as raw materials, and performing a single esterification reaction to generate monomethyl succinate to obtain a reaction solution A;

in this step, the reaction conditions are selected from at least one of (I) to (V):

the molar ratio of the succinic acid to the methanol is 1: (2-3);

The catalyst (II) is acid cation exchange resin, sulfate esterification catalyst or p-toluenesulfonic acid, specifically, the acid cation exchange resin comprises macroporous strong acid cation exchange resin, cation exchange resin with sulfonic group and the like, the sulfate esterification catalyst comprises ferric sulfate, tin sulfate, potassium hydrogen sulfate and the like, and the catalyst can also be common esterification catalyst such as concentrated sulfuric acid, concentrated hydrochloric acid, thionyl chloride, trifluoromethanesulfonic acid and the like;

(III) based on the total mass of succinic acid and methanol in the step (1), the catalyst is used in an amount of 0.5-3%;

(IV) heating temperature is 68-95 ℃;

(V) reflux reaction for 2-3.5 h.

(2) Distilling the reaction solution A under reduced pressure, separating methanol from water to obtain a reaction system, adding methanol after the distillation is completed, and performing secondary esterification reaction to generate dimethyl succinate;

in the step, distilled fractions are recovered, distilled fractions are rectified, methanol and water are sequentially rectified, the rectified residual liquid is applied to the step (1), and the distilled methanol is applied to one or more steps of the step (1), the step (2) and the step (3).

In this step, the reaction conditions are selected from at least one of (VI) to (VIII):

(VI) the molar ratio of the monomethyl succinate to the added methanol is 1: (2-3);

(VII) vacuum distillation is carried out under reduced pressure, wherein the vacuum degree is 20-60 mm Hg;

and (VIII) after methanol is added, reflux reaction is carried out for 1.5 to 2.5 hours at the temperature of 68 to 95 ℃.

(3) Repeating the step (2) at least once until the content of monomethyl succinate in the reaction system is less than or equal to 1%, so as to obtain a reaction solution B;

In the step, the molar ratio of the monomethyl succinate to the added methanol is 1: (5-6).

(4) Carrying out reduced pressure distillation on the reaction liquid B, separating methanol from water to obtain a reaction system, and obtaining a dimethyl succinate crude product; distilling the crude product of dimethyl succinate under reduced pressure, and separating to obtain a dimethyl succinate product, kettle residues and methanol with water;

In this step, the reaction conditions are selected from at least one of (IX) to (XI):

(IX) distilling the reaction solution B under reduced pressure, wherein the vacuum degree is 20-60 mm;

(X) distilling the crude dimethyl succinate under reduced pressure with a vacuum of <20mm;

(XI) the crude dimethyl succinate was distilled under reduced pressure at 60 ℃.

(5) And (3) applying the residue in the step (4) and part of the water-carrying methanol to the step (1), and applying the rest of the water-carrying methanol to the step (2).

In the step, the whole residue is applied to the step (1), and preferably, the ratio of the methanol added to the belts applied to the step (1) and the step (2) is 1:1, based on the molar amount of aqueous methanol.

In some embodiments, the source of additional methanol is one or more of fresh methanol, distilled methanol, and aqueous methanol separated in step (4).

FIG. 1 is a flow chart of a method for synthesizing dimethyl succinate by continuously applying fractions according to the application, as shown in FIG. 1, the synthesis flow of the application comprises: succinic acid, a catalyst and methanol are used as raw materials, and the succinic acid dimethyl ester product is obtained through primary reaction, secondary reaction, tertiary reaction and refining, and the method comprises the following steps:

The primary reaction comprises a monoesterification reaction and a secondary esterification reaction: adding succinic acid, a catalyst and methanol into a reaction kettle, uniformly mixing, heating and refluxing under normal pressure, and performing monoesterification reaction to generate monomethyl succinate to obtain a reaction solution A;

Distilling the reaction solution A under reduced pressure, adding methanol, heating and refluxing, and performing secondary esterification reaction to obtain dimethyl succinate; in the process, the distilled first-stage fraction is recovered and rectified, methanol and water are rectified in sequence, the rectified kettle residue is used in the single esterification reaction in the first-stage reaction, and the distilled methanol is used in one or more steps of the second esterification reaction, the second reaction and the third reaction in the first-stage reaction. Meanwhile, the distilled water is recycled by using a wastewater treatment device.

And (3) repeating the secondary esterification reaction, namely, the secondary reaction, on the material obtained by the primary reaction, and carrying out reduced pressure distillation and heating reflux to promote the balance of the reversible esterification reaction of the monomethyl succinate and the methanol to shift rightwards, so that the content of the monomethyl succinate in the reaction system is reduced, and a large amount of dimethyl succinate is generated to obtain a reaction solution B with the monomethyl succinate content less than or equal to 1%, thereby avoiding the need of separately separating the monomethyl succinate. Continuously distilling out second-stage fraction in the second-stage reaction process, recovering and rectifying, sequentially rectifying methanol and water, and applying the rectified kettle residue to a single esterification reaction, and applying the distilled methanol to one or more steps of the second-stage esterification reaction, the second-stage reaction and the third-stage reaction. Meanwhile, the distilled water is recycled by using a wastewater treatment device.

In the first-stage reaction and the second-stage reaction, methanol and water in the reaction system are continuously distilled out, so that the water content in the reaction system is low, and the obtained dimethyl succinate is low in water content; and the distilled methanol does not contain water, so that the water content in the reaction system is not increased when the methanol is sleeved.

And (3) repeating the secondary esterification reaction, namely the tertiary reaction, on the material obtained by the secondary reaction. In the third-stage reaction process, the amount of the added methanol is larger than that of the second-stage reaction. Because the reaction difficulty is gradually increased along with the increase of the esterification reaction times, methanol is excessively added to promote the reaction, and the water concentration in a reaction system is reduced; at the same time, excess make-up methanol can be distilled off to ensure that the molar amount of methanol applied to the primary and secondary reactions is sufficient to effect esterification when separated during reduced pressure distillation.

And (3) carrying out reduced pressure distillation on the reaction liquid B under the condition of the first vacuum degree, wherein the fraction is methanol with water, and the obtained material is a crude product of dimethyl succinate. Part of the water-carrying methanol is used as a raw material in the primary reaction, and the rest of the water-carrying methanol is used as one of sources of the supplementary methanol in the secondary reaction, so that the consumption of fresh methanol is reduced.

In the above flow, the source of the additional methanol is one or more of fresh methanol, rectified methanol and water-carrying methanol distilled by three-stage reaction.

And (3) distilling the crude product of the dimethyl succinate obtained by the three-stage reaction under reduced pressure at a second vacuum degree, and refining to obtain the dimethyl succinate product (the content is more than 99.5%) in the refining process, wherein the residual kettle residues (most of the dimethyl succinate and the little of the succinic acid) in the kettle are used in the monoesterification reaction.

The process is to continuously synthesize dimethyl succinate through the repeated application of the one-to-three-stage reaction, refining and fractions.

The invention also provides a device for synthesizing dimethyl succinate by continuously applying the fractions, which comprises a first-stage reaction system, a second-stage reaction system, a third-stage reaction system and a refining system which are sequentially arranged along the reaction direction, wherein the first-stage reaction system is a place for carrying out single esterification reaction on succinic acid and methanol, removing moisture in the reaction system and carrying out secondary esterification reaction to generate dimethyl succinate; the secondary reaction system is a place for repeatedly carrying out secondary esterification reaction, removing water in the reaction system and reducing the content of monomethyl succinate in the reaction system; the third-stage reaction system separates methanol and water from the reaction system through reduced pressure distillation to prepare a dimethyl succinate crude product, and the distilled fraction is applied to the sites of the first-stage reaction system and the second-stage reaction system; the refining system is used for refining the crude product of the dimethyl succinate by reduced pressure distillation, and the refined crude product is applied to the place where the residue is left in the first-stage reaction system.

In some embodiments, as shown in fig. 2, the first-stage reaction system of the present embodiment includes a first-stage reaction vessel R101, a first feed pump P101, a first reduced pressure distillation column T101, a first distillation condenser E101, and a first fraction collection tank V101, which are sequentially connected in the reaction direction.

Specifically, the first-stage reaction kettle R101 may be a stirred tank reactor, and the feed inlets of the first-stage reaction kettle R101 are respectively provided with a plurality of feed pipelines including a succinic acid feed pipeline, a catalyst feed pipeline, a methanol feed pipeline and the like. Succinic acid, a catalyst and methanol are conveyed into a first-stage reaction kettle R101 through a plurality of feed pipelines to be uniformly mixed, and then a single-esterification reaction and a secondary esterification reaction are carried out.

In addition, a first discharging pipeline is arranged at the bottom of the first-stage reaction kettle R101, a first transfer pump P101 is arranged on the first discharging pipeline, materials generated by the first-stage reaction kettle R101 are transferred to a first vacuum distillation tower T101 through the first transfer pump P101, and methanol and water are separated from a reaction system through controlling the vacuum degree so as to reduce the moisture content in the reaction system. The distilled methanol vapor and water vapor are condensed by the first distillation condenser E101 and collected by the first fraction collecting tank V101.

Specifically, the device of the embodiment also comprises a rectification system and a distillation vacuum pump P107, wherein the rectification system comprises a methanol recovery tower T104, a recovery condenser E104 and a methanol temporary storage tank V104 which are sequentially connected along the reaction direction.

The first fraction collecting tank V101 is connected with the methanol recovering tower T104 to rectify the distilled fraction of the first-stage reaction system, and based on the difference of the boiling points of the rectified fraction, the rectified methanol gas is liquefied by the recovering condenser E104 and is collected by the methanol temporary storage tank V104. And the distilled water is directly recycled by the wastewater treatment device. The first fraction collection tank V101 is also connected to a distillation vacuum pump P107, and the distillation vacuum pump P107 is used to evacuate air in the container during reduced pressure distillation to form a vacuum environment, and reduce the boiling point, thereby realizing separation.

In some embodiments, as shown in fig. 2, the secondary reaction system includes a secondary reaction vessel R102, a second transfer pump P102, a second reduced pressure distillation column T102, a second distillation condenser E102, and a second fraction collection tank V102, which are sequentially connected in the reaction direction.

Specifically, the secondary reaction vessel R102 may be a stirred tank reactor. The bottom pipeline of the first reduced pressure distillation tower T101 is connected with the feed inlet of the secondary reaction kettle R102, so that the materials of which the water and the methanol are removed by the primary reaction system are conveyed to the secondary reaction kettle R102 for repeated secondary esterification reaction, and the content of monomethyl succinate in the reaction system is continuously reduced. In this process, additional methanol is needed, so a methanol feed pipeline (not shown in the figure, the additional methanol is fresh methanol for the primary preparation) is also arranged at the feed inlet of the secondary reaction kettle R102.

Specifically, a second discharging pipeline is arranged at the bottom of the secondary reaction kettle R102, a second transfer pump P102 is arranged on the second discharging pipeline, materials generated by the secondary reaction kettle R102 are transferred to a second vacuum distillation tower T102 through the second transfer pump P102, and methanol and water are separated from a reaction system through controlling the vacuum degree so as to reduce the moisture content in the reaction system. The distilled methanol vapor and water vapor are condensed by the second distillation condenser E102 and collected by the second fraction collection tank V102.

Specifically, the second fraction collecting tank V102 is connected to the methanol recovering column T104 to rectify the distilled fraction of the second-stage reaction system, and based on the difference in boiling point of the rectified fraction, the rectified methanol gas is liquefied by the recovery condenser E104 and collected by the methanol temporary storage tank V104. And the distilled water is directly recycled by the wastewater treatment device. The second fraction collection tank V102 is also connected to a distillation vacuum pump P107.

In some embodiments, as shown in fig. 2, the three-stage reaction system includes a three-stage reaction kettle R103, a third transfer pump P103, a third reduced pressure distillation column T102, a third distillation condenser E103, and a third fraction collection tank V103, which are sequentially connected in the reaction direction.

Specifically, the tertiary reaction vessel R103 may be a stirred tank reactor. The bottom pipeline of the second reduced pressure distillation tower T102 is connected with the feed inlet of the third-stage reaction kettle R103, so that materials with water, methanol and low monomethyl succinate content in the second-stage reaction system are conveyed to the third-stage reaction kettle R103 for re-esterification reaction, and a crude dimethyl succinate product is prepared. In the process, the methanol is required to be added, so that the feed inlet of the three-stage reaction kettle R103 is also provided with a plurality of methanol adding pipelines, including a first methanol adding pipeline and a second methanol adding pipeline. The first methanol make-up line was used to deliver fresh methanol to the three stage reactor R103. One end of the second methanol supplementing pipeline is connected to the methanol temporary storage tank V104, the other end of the second methanol supplementing pipeline is connected to a feed inlet of the three-stage reaction kettle R103, a fourth transfer pump P104 is further arranged on the second methanol supplementing pipeline, and the distilled methanol is sleeved in the three-stage reaction kettle R103 to serve as the supplementing methanol for esterification reaction under the action of the fourth transfer pump P104.

Specifically, a third discharging pipeline is arranged at the bottom of the three-stage reaction kettle R103, a third transfer pump P103 is arranged on the third discharging pipeline, materials generated by the three-stage reaction kettle R103 are transferred to a third vacuum distillation tower T102 through the third transfer pump P103, and methanol and water are separated from the system through controlling the vacuum degree. The distilled aqueous methanol is condensed by the third distillation condenser E103 and collected by the third fraction collecting tank V103.

Specifically, the third fraction collection tank V103 is connected to the distillation vacuum pump P107. The third fraction collection tank V103 is also connected with the first-stage reaction kettle R101 and the second-stage reaction kettle R102 in a pipeline manner so as to apply the methanol with water as the additional methanol to the first-stage reaction kettle R101 and the second-stage reaction kettle R102 to participate in the esterification reaction.

In some embodiments, as shown in fig. 2, the refining system includes a product distillation column T105, a product condenser E105, a product collection tank V105, and a product distillation vacuum pump P106 connected in that order along the reaction direction.

Specifically, the third reduced pressure distillation column T102 is pipe-connected to the product distillation column T105. The bottom of the third vacuum distillation tower T102 is provided with a fourth discharge pipeline, a fifth transfer pump P105 is arranged on the fourth discharge pipeline, the crude dimethyl succinate generated by the three-stage reaction system is transferred into the product distillation tower T105 for refining through the fifth transfer pump P105, and the dimethyl succinate is separated out and condensed by the product condenser E105 through controlling the vacuum degree and is collected by the product collecting tank V105. The bottom pipeline of the product distillation tower T105 is connected with the feed inlet of the first-stage reaction kettle R101, so that the refined kettle residue is used in the first-stage reaction kettle R101 as a raw material to participate in the esterification reaction again.

Specifically, the product collection tank V105 is further provided with a product discharge pipe and is connected with a circulating water cooling system to improve the condensing effect. The product collection tank V105 is also connected to a tail gas treatment system to recover and treat the tail gas produced during distillation.

The invention discloses a method and a device for synthesizing dimethyl succinate by continuously applying fractions, and specific examples of synthesizing dimethyl succinate are as follows.

The present invention will be described in detail with reference to specific exemplary examples. It is also to be understood that the following examples are given solely for the purpose of illustration and are not to be construed as limitations upon the scope of the invention, as many insubstantial modifications and variations are within the scope of the invention as would be apparent to those skilled in the art in light of the foregoing disclosure. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below.

Example 1

Adding 118.4g (1 mol) of succinic acid, 80g (2.5 mol) of methanol and 1.2g (1%) of ferric sulfate into a reaction kettle, uniformly mixing, heating to 80 ℃ under normal pressure, and carrying out monoesterification for 3 hours to generate monomethyl succinate, thus obtaining a reaction liquid A;

vacuum distilling the reaction solution A to vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; adding 80g (2.5 mol) of methanol after the distillation is completed, and performing secondary esterification reaction at 80 ℃ for 1.5-2 h to generate dimethyl succinate;

vacuum distilling again with vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; 160g (5.0 mol) of methanol is added after the distillation is completed, and the reaction is carried out for 1.5 to 2 hours at the temperature of 80 ℃, at this time, the content of monomethyl succinate in the reaction system is monitored to be less than or equal to 1 percent, and a reaction liquid B is obtained;

Carrying out reduced pressure distillation on the reaction liquid B, separating methanol and water from a system, and obtaining a crude product, wherein the vacuum degree is 60mm Hg;

And (3) carrying out reduced pressure distillation on the crude product, separating to obtain the product dimethyl succinate, kettle residues and water-carrying methanol, wherein the kettle residues and 50% of the water-carrying methanol (based on the molar weight of the water-carrying methanol) are applied to a monoesterification reaction, and the remaining 50% of the water-carrying methanol is applied to a secondary esterification reaction, and distilling the product.

134.6G of dimethyl succinate product, 99.89 percent of content and 92.09 percent of yield are collected, and 2.5g of kettle residue;

1.7g of residual materials (residual liquid) in the kettle after rectification.

The residual liquid, the kettle residual, the distilled partial methanol and 50% of the water-carrying methanol (based on the molar amount of the water-carrying methanol) are applied to the monoesterification reaction, and the residual 50% of the water-carrying methanol and the distilled partial methanol are applied to the secondary esterification reaction.

After application of the fractions, the yield of the synthesized product was 96.18%.

Example 2

Adding 118.4g (1 mol) of succinic acid, 80g (2.5 mol) of methanol and 1.8g (1.5%) of p-toluenesulfonic acid into a reaction kettle, uniformly mixing, heating to 82 ℃ under normal pressure, and carrying out monoesterification reaction for 2 hours to generate monomethyl succinate, thus obtaining reaction liquid A;

vacuum distilling the reaction solution A to vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; adding 80g (2.5 mol) of methanol after the distillation is completed, and performing secondary esterification reaction at 80 ℃ for 1.5-2 h to generate dimethyl succinate;

vacuum distilling again with vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; 160g (5.0 mol) of methanol is added after the distillation is completed, and the reaction is carried out for 1.5 to 2 hours at the temperature of 80 ℃, at this time, the content of monomethyl succinate in the reaction system is monitored to be less than or equal to 1 percent, and a reaction liquid B is obtained;

Carrying out reduced pressure distillation on the reaction liquid B, separating methanol and water from a system, and obtaining a crude product, wherein the vacuum degree is 60mm Hg;

And (3) carrying out reduced pressure distillation on the crude product, separating to obtain the product dimethyl succinate, kettle residues and water-carrying methanol, wherein the kettle residues and 50% of the water-carrying methanol (based on the molar weight of the water-carrying methanol) are applied to a monoesterification reaction, and the remaining 50% of the water-carrying methanol is applied to a secondary esterification reaction, and distilling the product.

Collecting 134.9g of dimethyl succinate, 99.79% of content and 92.20% of yield, and 2.9g of residue;

1.6g of residual materials (residual liquid) in the kettle after rectification.

The residual liquid, the kettle residual, the distilled partial methanol and 50% of the water-carrying methanol (based on the molar amount of the water-carrying methanol) are applied to the monoesterification reaction, and the residual 50% of the water-carrying methanol and the distilled partial methanol are applied to the secondary esterification reaction.

After the fractions were used, the yield of the synthesized product was 96.89%.

Example 3

Adding 118.4g (1 mol) of succinic acid, 80g (2.5 mol) of methanol and 3.6g (3%) of macroporous strong acid cation exchange resin into a reaction kettle, uniformly mixing, heating to 80 ℃ under normal pressure, and carrying out monoesterification for 3 hours to generate monomethyl succinate to obtain a reaction solution A;

vacuum distilling the reaction solution A to vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; adding 80g (2.5 mol) of methanol after the distillation is completed, and performing secondary esterification reaction at 80 ℃ for 1.5-2 h to generate dimethyl succinate;

vacuum distilling again with vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; 160g (5.0 mol) of methanol is added after the distillation is completed, and the reaction is carried out for 1.5 to 2 hours at the temperature of 80 ℃, at this time, the content of monomethyl succinate in the reaction system is monitored to be less than or equal to 1 percent, and a reaction liquid B is obtained;

Carrying out reduced pressure distillation on the reaction liquid B, separating methanol and water from a system, and obtaining a crude product, wherein the vacuum degree is 60mm Hg;

And (3) carrying out reduced pressure distillation on the crude product, separating to obtain the product dimethyl succinate, kettle residues and water-carrying methanol, wherein the kettle residues and 50% of the water-carrying methanol (based on the molar weight of the water-carrying methanol) are applied to a monoesterification reaction, and the remaining 50% of the water-carrying methanol is applied to a secondary esterification reaction, and distilling the product.

133.8G of dimethyl succinate product, 99.86 percent of content and 91.51 percent of yield are collected, and 4.7g of kettle residue is left;

1.7g of residual materials (residual liquid) in the kettle after rectification.

The residual liquid, the kettle residual, the distilled partial methanol and 50% of the water-carrying methanol (based on the molar amount of the water-carrying methanol) are applied to the monoesterification reaction, and the residual 50% of the water-carrying methanol and the distilled partial methanol are applied to the secondary esterification reaction.

After the fractions were used, the yield of the synthesized product was 95.13%.

Comparative example 1

Adding 118.4g (1 mol) of succinic acid, 480g (15 mol) of methanol and 1.2g (1%) of ferric sulfate into a reaction kettle, uniformly mixing, heating to 80 ℃ under normal pressure, and detecting that the succinic acid content in a reaction system is 4.22% after the monoesterification reaction is carried out for 9 hours;

Adding 160g (5 mol) of methanol for continuous secondary esterification reaction for 2 hours, and detecting that the succinic acid content is 3.20%; vacuum distillation, vacuum degree of 60 mmHg, separating methanol and water from the reaction system, continuing distillation, and collecting 128.28g of dimethyl succinate product with content of 95.89% and yield of 84.25%.

Comparative example 2

Adding 118.2g (1 mol) of succinic acid, 480g (15 mol) of methanol and 1.8g (1.5%) of p-toluenesulfonic acid into a reaction kettle, uniformly mixing, heating to 81 ℃ under normal pressure, carrying out monoesterification reaction for 3 hours, carrying out reduced pressure distillation, carrying out vacuum degree of 60mm Hg, distilling out fraction, and recovering methanol;

After the distillation is completed, 480g (15 mol) of methanol is added, after the secondary esterification reaction is carried out for 1.5 to 2 hours at 80 ℃, the vacuum distillation is carried out, the vacuum degree is 60mm Hg, the fraction is distilled out, the methanol is recovered, the vacuum distillation is continued, and 130.1g of dimethyl succinate product with the content of 99.36 percent and the yield of 88.54 percent is obtained.

Comparative example 3

Adding 118.3g (1 mol) of succinic acid, 80g (2.5 mol) of methanol and 3.6g (3%) of macroporous strong acid cation exchange resin into a reaction kettle, uniformly mixing, heating to 80 ℃ under normal pressure, and carrying out monoesterification for 3 hours to generate monomethyl succinate to obtain a reaction solution A;

vacuum distilling the reaction solution A to vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; adding 80g (2.5 mol) of methanol after the distillation is completed, and performing secondary esterification reaction at 80 ℃ for 1.5-2 h to generate dimethyl succinate;

vacuum distilling again with vacuum degree of 60 mmHg, separating methanol and water out of the reaction system, collecting fraction, rectifying, and sequentially rectifying methanol and water; 160g (5.0 mol) of methanol is added after the distillation is completed, and the reaction is carried out for 1.5 to 2 hours at the temperature of 80 ℃, at this time, the content of monomethyl succinate in the reaction system is monitored to be less than or equal to 1 percent, and a reaction liquid B is obtained;

Carrying out reduced pressure distillation on the reaction liquid B, separating methanol and water from a system, and obtaining a crude product, wherein the vacuum degree is 60mm Hg;

the crude product was distilled under reduced pressure at a vacuum of 18mm Hg and a temperature of 60℃to yield 133.0g of dimethyl succinate, 99.76% and a yield of 90.88%.

As can be seen from the examples and the comparative examples, the molar ratio of succinic acid to the total amount of methanol in the whole reaction system of the preparation method of the application is 1:10, the content of the prepared dimethyl succinate product is about 99.8%, the yield is more than 91%, and after the recovered methanol, the recovered material and the kettle residue are used mechanically, the yield of the product can be further improved, the yield is improved to more than 95%, and the moisture is less than 0.08%. The preparation method has the advantages of small methanol consumption and small methanol recovery after the reaction is finished, so that the energy consumption of the whole preparation process is low. The product prepared by the preparation method has high purity and low moisture content.

And the molar ratio of succinic acid to the total amount of methanol in the whole reaction system of comparative example 1 is 1:20, methanol and water are separated by one-time distillation, the content of the prepared dimethyl succinate product is about 95%, and the yield is about 84%, and compared with the embodiment, the content and the yield of the product are greatly reduced, the methanol consumption is large, and the energy consumption in the preparation process is high.

Comparative example 2 the molar ratio of succinic acid to the total amount of methanol in the whole reaction system was 1:20, separating methanol and water by twice distillation, wherein the prepared dimethyl succinate product has higher content, but low yield, large methanol consumption and high energy consumption in the preparation process.

Compared with the example, the comparative example 3 has no need of using residue and recovered materials, and the yield of the prepared dimethyl succinate product is greatly reduced compared with that after the use.

The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims (10)

1. A method for synthesizing dimethyl succinate by continuously applying fractions, which is characterized by comprising the following steps:

(1) Taking succinic acid, methanol and a catalyst as raw materials, and performing a single esterification reaction to generate monomethyl succinate to obtain a reaction solution A;

(2) Decompressing and distilling the reaction liquid A, separating methanol from water to obtain a reaction system, adding methanol after finishing distillation, and performing secondary esterification reaction to generate dimethyl succinate;

(3) Repeating the step (2) at least once until the content of monomethyl succinate in the reaction system is less than or equal to 1%, so as to obtain a reaction solution B;

(4) Performing reduced pressure distillation on the reaction liquid B, separating methanol from water to obtain a reaction system, and obtaining a dimethyl succinate crude product; distilling the crude dimethyl succinate product under reduced pressure, and separating to obtain a dimethyl succinate product, kettle residues and methanol with water;

(5) And (3) applying the residue in the step (4) and part of the water-carrying methanol to the step (1), and applying the rest of the water-carrying methanol to the step (2).

2. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, further comprising recovering the fraction distilled in the step (2), rectifying the fraction, sequentially rectifying methanol and water, applying the rectified residual liquid to the step (1), and applying the rectified methanol to one or more of the steps (1), (2) and (3).

3. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the molar ratio of succinic acid to methanol in the step (1) is 1: (2-3).

4. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the molar ratio of monomethyl succinate to additional methanol in the step (2) is 1: (2-3).

5. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the molar ratio of monomethyl succinate to additional methanol in the step (3) is 1: (5-6).

6. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the catalyst in the step (1) is an acidic cation exchange resin, a sulfate esterification catalyst or p-toluenesulfonic acid.

7. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the reaction condition of the step (1) is selected from at least one of the following (i) to (iii):

Heating temperature is 68-95 ℃;

(II) reflux reaction is carried out for 2 to 3.5 hours;

(III) the catalyst is used in an amount of 0.5 to 3% based on the total mass of succinic acid and methanol in the step (1).

8. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 1, wherein the reaction condition of the step (2) is selected from at least one of the following (iv) to (v):

(IV) the vacuum degree of reduced pressure distillation is 20-60 mmHg;

and (V) adding methanol, and then carrying out reflux reaction for 1.5-2.5 h at 68-95 ℃.

9. The method for synthesizing dimethyl succinate by continuously applying the fraction according to claim 2, wherein the source of the additional methanol is one or more of fresh methanol, distilled methanol, and water-bearing methanol separated in the step (4).

10. The device for synthesizing the dimethyl succinate by continuously applying the fractions is characterized by comprising a primary reaction system, a secondary reaction system, a tertiary reaction system and a refining system which are sequentially arranged along the reaction direction, wherein the primary reaction system is a place for carrying out monoesterification reaction on succinic acid and methanol, removing moisture in the reaction system and carrying out secondary esterification reaction to generate the dimethyl succinate; the secondary reaction system is a place for repeatedly carrying out secondary esterification reaction, removing water in the reaction system and reducing the content of monomethyl succinate in the reaction system; the three-stage reaction system is used for separating methanol from water through reduced pressure distillation to obtain a reaction system, preparing a dimethyl succinate crude product, and applying distilled fractions to the sites of the first-stage reaction system and the second-stage reaction system; the refining system is used for refining the crude product of the dimethyl succinate by reduced pressure distillation, and the refined crude product is applied to the place where the residue of the kettle is left to the primary reaction system.