A continuous process for the production of diethyl maleate

Abstract

The application relates to the technical field of diethyl maleate preparation, in particular to a continuous production method of diethyl maleate, which comprises the following steps: S1: anhydrous maleic acid and ethanol are introduced into a monoester reactor to obtain a stream A; S2: the stream A is introduced into a diester reactor to obtain a stream B; S3: the stream B and ethanol are introduced into a reaction rectifying tower to obtain streams H and C; S4: the stream C comprises streams D, E and F, the ethanol and water removed from the stream D form a stream I, and the rest is diethyl maleate; S5: the stream E is introduced into the reaction rectifying tower to continue the reaction; the stream F is heated to become a stream G, and then is continuously reacted by being introduced from the bottom of the tower; S6: the stream H and the stream I are treated through a permeation membrane device to obtain a stream J, the stream J is collected and then introduced into the monoester reactor as raw material; and S7: the diethyl ether in the stream J is rectified and collected in the monoester reactor. The preparation method has the advantages of continuous removal of diethyl ether by-products, simple operation and high efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diethyl maleate preparation, and more particularly to a continuous production method of diethyl maleate. BACKGROUND

[0002] The current main production method of diethyl maleate is intermittent production, using a single reaction kettle, and simultaneously performing mono-esterification and di-esterification reactions, which has low production efficiency. Meanwhile, most strong acids, such as sulfuric acid and p-toluenesulfonic acid, are used as catalysts, which are strongly corrosive, and the catalysts often form three wastes together with the crude product after neutralization; cyclohexane and toluene are used as water-carrying agents in the esterification process, which can affect product purity and cause environmental pollution. This type of process has the disadvantages of low production efficiency, easy corrosion of equipment, inability to reuse catalysts, and large amount of three waste emissions.

[0003] In related technologies, in the industrial production process of diethyl maleate, maleic anhydride and ethanol generate maleic acid monoethyl ester in a reaction kettle, and then maleic acid monoethyl ester and ethanol further react to obtain diethyl maleate. In the high-temperature esterification process of maleic acid monoethyl ester and ethanol, a side reaction inevitably occurs, that is, ethanol undergoes an etherification side reaction under high-temperature and acidic conditions.

[0004] The dehydration etherification of ethanol under high-temperature and acidic conditions can be described by the following equation.

[0005] Currently, diethyl maleate cannot effectively remove the byproduct diethyl ether in industrial production, and therefore, diethyl ether is enriched in the system during the reaction process, thereby reducing the esterification efficiency of diethyl maleate. SUMMARY

[0006] The technical problem to be solved by the present application is that the production of diethyl maleate produces diethyl ether byproducts in related technologies, thereby reducing the esterification efficiency of diethyl maleate. The present application provides a continuous production method of diethyl maleate. The continuous production method has the characteristics of continuously removing diethyl ether byproducts, simple production operation, and high production efficiency.

[0007] The present application provides a continuous production method of diethyl maleate, which adopts the following technical scheme:

[0008] A continuous production method of diethyl maleate, comprising the following steps:

[0009] S1: maleic anhydride and first ethanol enter a mono-esterification reactor to obtain a stream A;

[0010] S2: the stream A further enters a di-esterification reactor for esterification to obtain a stream B;

[0011] S3: the stream B is fed into the reaction distillation column from the reaction distillation column, at the same time, the second ethanol is fed into the reaction distillation column from the bottom of the reaction distillation column; the stream H is taken out from the top of the column, and the stream C is taken out from the bottom of the column;

[0012] S4: the stream C is divided into the stream D, the stream E and the stream F, wherein the stream D is fed into the thin film evaporator to remove the ethanol and water to obtain the diethyl maleate product, the removed ethanol and water are pressurized by a pump and then transported into the vapor permeation membrane device through a pipeline together with the stream H in S3, the stream E is transported to the reaction distillation column through a pipeline to carry out a circulation reaction;

[0013] S5: the reaction distillation column is provided with a reboiler, and the stream F returns to the bottom of the reaction distillation column after flowing through the reboiler;

[0014] S6: after the stream H and the stream I are treated by the vapor permeation membrane device, the stream J mainly containing ethanol and ether is obtained, the stream J is condensed and collected, and then enters the monoester reaction kettle;

[0015] S7: the monoester reaction kettle is provided with a horizontal condenser, and the ether component in the stream J is evaporated by heating in the monoester reaction kettle and is condensed and collected in an ether collection tank by the horizontal condenser.

[0016] More preferably, the mass ratio of the stream D, the stream E and the stream F is 1:2:(5-6).

[0017] Preferably, the stream A is a mixture of maleic acid monoethyl ester, maleic anhydride and ethanol.

[0018] Preferably, the stream B is a mixture of diethyl maleate, maleic acid monoethyl ester and ethanol.

[0019] Preferably, the stream C is a mixture of diethyl maleate, a small amount of maleic acid monoethyl ester, ethanol and water.

[0020] By adopting the technical scheme, the application discloses a production method of maleic acid diethyl ester, a new process for continuously producing maleic acid diethyl ester is developed, ethanol is dehydrated and etherified to generate diethyl ether in the double ester reactor and the reaction rectifying tower, therefore, the diethyl ether is contained in the stream H, the stream C is divided into three parts, namely, the stream D, the stream E and the stream F, the water and the ethanol in the stream D are removed through a thin film evaporator and are condensed to obtain the crude maleic acid diethyl ester, the water and the ethanol are collected after being condensed, the stream H is removed through a steam permeation membrane device, only the stream J containing the ethanol and the diethyl ether is left, then the stream J is transported to the monoester reaction kettle through a pipeline, the ethanol in the stream J is continuously esterified with maleic anhydride in the monoester reaction kettle, the esterification reaction is exothermic, the ethanol and the diethyl ether in the reaction kettle are evaporated by heat, the temperature of the vertical condenser is controlled, the ethanol is cooled and flows back to the kettle to continue the reaction, and the diethyl ether continues to rise to the horizontal condenser and is condensed and collected in the receiving tank.

[0021] In the application, the monoesterification reaction kettle does not need to be heated from the outside under the condition of stable operation, and only the heat released by the esterification can maintain the monoesterification reaction temperature, and the diethyl ether in the kettle can be evaporated and removed, the evaporated diethyl ether is cooled and collected by the stream J with a lower temperature (-5-10 DEG C), and no additional cooling agent needs to be introduced from the outside, thereby achieving energy saving and consumption reduction in design.

[0022] In addition, the continuous esterification production process of maleic acid diethyl ester is combined with the steam permeation membrane technology for dehydration, the production efficiency of the esterification reaction of maleic acid diethyl ester and the dehydration efficiency of ethanol are improved, the yield of maleic acid diethyl ester is improved, and the energy loss in the reaction process is reduced; meanwhile, the by-product diethyl ether in the esterification reaction is effectively removed without increasing the energy consumption, thereby reducing the enrichment of the diethyl ether in the continuous production system of maleic acid diethyl ester, and further improving the esterification efficiency of maleic acid diethyl ester.

[0023] In the application, the stream B is fed from the double ester reactor, the light components (ethanol and water) are separated from bottom to top; the heavy components, namely, the maleic anhydride and the maleic acid monoethyl ester, are separated from top to bottom, and form a countercurrent with the ethanol added in the kettle bottom (from bottom to top) to further esterify under the catalysis of the catalyst, thereby improving the esterification speed; in addition, when the stream B flows out of the double ester reactor, the temperature is lower than that in the reaction rectifying tower, when the stream B enters the reaction rectifying tower, the temperature of the whole reaction rectifying tower is lowered, which is not conducive to the subsequent esterification reaction; in order to improve the esterification efficiency, the stream E with a higher temperature needs to be transported to the reaction rectifying tower for forced heating to improve the reaction temperature of the reaction rectifying tower, thereby improving the double esterification degree.

[0024] Preferably, in S6, the stream J collected after condensation is designed to pass through a horizontal condenser to serve as a refrigerant due to its low temperature.

[0025] Preferably, a carrier plate is arranged in the column of the reaction rectifying tower, and the carrier plate is loaded with a solid catalyst.

[0026] By adopting the technical scheme, when the stream B and the stream E enter the column of the reaction rectifying tower, the ethanol and water components in the stream B and the stream E are boiled and rise from the top of the column, and the monoethyl maleate component flows from top to bottom, can fully contact with the ethanol vaporized from the bottom of the reaction rectifying tower in the column, and the monoethyl maleate and the ethanol can be subjected to a secondary esterification reaction under the catalysis of the solid catalyst on the carrier plate to obtain the diethyl maleate.

[0027] Preferably, the monoester reaction kettle is provided with a stirring device, a temperature rising and falling device, and a vertical condenser, the vertical condenser is arranged in the monoester reaction kettle to condense ethanol, the temperature of the monoester reaction kettle is controlled to be between 50-80℃, and the temperature of the vertical condenser is controlled to be between 35-45℃.

[0028] Preferably, the temperature of the stream J is between -5 to +10℃.

[0029] More preferably, the temperature of the monoester reaction kettle is 70℃, and the temperature of the vertical condenser is 40℃.

[0030] By adopting the technical scheme, the stream J mainly contains ethanol and diethyl ether, and it is known that the boiling point of diethyl ether is 34.5℃, and the boiling point of ethanol is 78.3℃, when the stream J continuously enters the monoester reaction kettle, the ethanol is condensed and recovered into the monoester reaction kettle to continue to react with maleic anhydride through the vertical condenser, and the diethyl ether is in a gaseous state in the monoester reaction kettle, passes through the vertical condenser to the horizontal condenser, and is condensed and recovered in the horizontal condenser, so as to remove the diethyl ether from the continuous production system of diethyl maleate.

[0031] Preferably, the diester reactor is a fixed bed reactor, the diester reactor is provided with a solid catalyst, the reaction temperature in the diester reactor is controlled to be between 80-130℃, and the reaction pressure is 0.3-1.0MPa.

[0032] Preferably, the solid catalyst loaded in the diester reactor and the reaction rectifying tower is the same catalyst.

[0033] More preferably, the solid catalyst is a strong acid cation exchange resin.

[0034] By adopting the technical scheme, the reaction temperature in the double ester reactor is controlled to be 80-130 DEG C, and the reaction pressure is 0.3-1.0 MPa, so that the secondary esterification reaction of the maleic acid monoethyl ester and the ethanol under the catalysis of the solid catalyst is better carried out.

[0035] Preferably, the reaction rectification tower bottom is further provided with a temperature rising and falling device.

[0036] By adopting the technical scheme, the maleic acid monoethyl ester remaining in the reaction rectification tower bottom can be re-heated by the temperature rising and falling device, and the heated maleic acid monoethyl ester is continuously fed from the tower to be esterified into the maleic acid diethyl ester; the stream F is heated by the reboiler to form the stream G which is transported to the bottom of the reaction rectification tower to provide the heat energy required by the reaction rectification tower.

[0037] Preferably, a heat supplement device is arranged at the front end of the vapor permeation membrane device, the stream I and the stream H are heated by the heat supplement device, and the temperature of the heat supplement device is controlled to be 99-120 DEG C.

[0038] Preferably, the membrane assembly used by the vapor permeation membrane device is a molecular sieve membrane.

[0039] By adopting the technical scheme, the temperature of the heat supplement device is controlled to be 99-120 DEG C, so that the stream I and the stream H can be heated, and the ethanol, the diethyl ether and the water are in a gaseous state and enter the vapor permeation membrane device, so that the vapor permeation membrane device removes the water component.

[0040] Preferably, the vapor permeation membrane device has a refrigerant liquid with a temperature of-5 to +10 DEG C.

[0041] By adopting the technical scheme, since the temperature of the refrigerant liquid is-5 to +10 DEG C, the ethanol, the diethyl ether and the water vapor in the stream J can be well condensed and recovered.

[0042] In summary, the present application has the following beneficial effects:

[0043] 1. The present application combines the continuous esterification production process of the maleic acid diethyl ester with the vapor permeation membrane technology dehydration, improves the production efficiency of the esterification reaction of the maleic acid diethyl ester and the dehydration efficiency of the ethanol, improves the yield of the maleic acid diethyl ester, and reduces the energy loss in the reaction process; at the same time, the by-product diethyl ether in the esterification reaction is effectively removed without increasing the energy consumption, thereby reducing the enrichment of the diethyl ether in the continuous production system of the maleic acid diethyl ester, and further improving the esterification efficiency of the maleic acid diethyl ester.

[0044] 2. The application designs a reaction rectification column with temperature rising and falling equipment at the bottom, an external reboiler, and a stream bypass (stream E), which fully guarantees the system's temperature rising and falling capacity, makes it easy to set / adjust the temperature adjustment requirements of each section of the reaction rectification column during operation, greatly enhances the system's running stability, and also facilitates the adjustment of the reflux ratio, effectively improves the material quality stability of the produced stream (stream D). BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a flow chart of the method provided by the application;

[0046] Figure 2 is the content of each component of stream A in the embodiment of the application;

[0047] Figure 3 is the content of each component of stream B in the embodiment of the application;

[0048] Figure 4 is the content of each component of stream C in the embodiment of the application;

[0049] Figure 5 is the content of each component of stream H in the embodiment of the application;

[0050] Figure 6 is the content of each component in the ether collection tank 4 in the embodiment of the application;

[0051] BRIEF DESCRIPTION OF DRAWINGS: 1, single ester reaction kettle; 2, vertical condenser; 3, horizontal condenser; 4, ether collection tank; 5, double ester reactor; 6, reboiler; 7, stream pump I; 8, reaction rectification column; 9, thin film evaporator; 10, condenser; 11, collection tank; 12, vacuum pump I; 13, ethanol pump I; 14, wastewater tank; 15, condenser I; 16, vacuum pump II; 17, heat compensator; 18, steam permeation membrane device; 19, condenser II; 20, ethanol collection tank; 21, ethanol pump II. DETAILED DESCRIPTION

[0052] The application will be further described in detail below in combination with the drawings and examples. It is specially pointed out that: in the following examples, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following examples can be sourced from ordinary commercial sales unless otherwise specified.

[0053] EXAMPLE

[0054] Example 1

[0055] Adopting Figure 1The process shown, open pump valve to make the outside of the male anhydride, ethanol and stream J (recycled ethanol) into the monoester reactor 1, open the monoester reactor 1 in the stirring device and temperature device, control the temperature of the monoester reactor 1 at about 70 DEG C, control the flow of each stream, so that the residence time of the stream in the monoester reactor 1 is controlled at 0.5 hours; control the cooling water flow of the vertical condenser 2 on the monoester reactor 1, so that the distillation temperature of the vertical condenser 2 is about 40 DEG C, so that the ethanol vapor in the stream J in the maleic acid diethyl ester continuous reaction system can be condensed into the monoester reactor 1 through the vertical condenser 2, and the ether vapor in the stream J can rise, pass through the vertical condenser 2 with a distillation temperature of about 40 DEG C and not condense, continue to rise, and after passing through the horizontal condenser 3, it is condensed and collected into the ether collection tank 4, and the distillation temperature of the horizontal condenser 3 is about-5 to +10 DEG C.

[0056] The monoester reactor 1 carries out monoesterification reaction on the maleic anhydride and ethanol to obtain stream A, wherein stream A is a mixture containing maleic acid monoethyl ester, maleic anhydride and ethanol, referring to Figure 2 It can be seen that the content of each component in stream A is: ethanol 69.8%, ether 1.53%, trans-maleic acid diethyl ester 0.41%, cis-maleic acid diethyl ester 14.37%, maleic acid monoethyl ester 9.97% and maleic anhydride 1.5%. Since the continuous production process is adopted in the present application, the residual ether in the monoester reactor 1 will enter stream A.

[0057] About 80% of the maleic anhydride in stream A is ring-opening esterification to become maleic acid monoethyl ester, and at this time the temperature of stream A is about 70 DEG C. Stream A enters the diester reactor 5, and the temperature of the diester reactor 5 is controlled at about 100 DEG C and the pressure is 0.7 MPa. Under this temperature and pressure, about 85% of the maleic anhydride in stream A is converted to maleic acid diethyl ester with maleic acid monoethyl ester, and stream B mainly containing maleic acid diethyl ester, maleic acid monoethyl ester and ethanol is obtained; referring to Figure 3 It can be seen that the content of each component in stream B is: ethanol 15.26%, ether 0.33%, trans-maleic acid diethyl ester 0.13%, cis-maleic acid diethyl ester 77.91%, maleic acid monoethyl ester 3.4% and maleic anhydride 0.64%.

[0058] Stream B enters the reaction rectification column 8, which is divided into top, middle and bottom sections, and stream B enters from the middle section, the temperature of the upper section of the reaction rectification column 8 is controlled at about 80-90 DEG C; the temperature in the middle section is controlled at about 90-120 DEG C; and the temperature at the bottom is controlled at about 120-150 DEG C; the middle section of the reaction rectification column 8 is provided with a carrier plate, and the carrier plate is loaded with a solid catalyst, wherein the solid catalyst is a strong acid cation exchange resin.

[0059] The reaction rectification column 8 is also added with external ethanol, which is fed into the reaction rectification column 8 from the bottom of the reaction rectification column 8, and then the stream B and the ethanol stream are further reacted in the reaction rectification column 8 while being subjected to heat and mass exchange. Under the catalysis of the strong acid cation exchange resin catalyst, the reaction obtains a stream C mainly containing diethyl maleate and a small amount of monoethyl maleate, ethanol and water, which flows out from the bottom of the column, and a stream H containing ethanol, water and a small amount of diethyl ether, which is collected from the top of the column. Figure 4 It is known that the content of each component in the stream C is: ethanol 1.32%, trans-diethyl maleate 0.28%, cis-diethyl maleate 97.74% and monoethyl maleate 0.07%; and the content of each component in the stream H is: ethanol 94.4% and diethyl ether 5.6%. Figure 5

[0060] Then, when the reaction acid value reaches the control index requirement, the opening stream pump I 7 is started to collect, and the stream C falling back to the bottom is divided into three streams D, E and F by forced circulation, wherein the stream F is reheated to about 120-150°C by the reboiler 6 to form a stream G, and then the stream G is added to the bottom of the reaction rectification column 8 to provide heat for the reaction of the reaction rectification column 8.

[0061] The temperature of the stream E separated from the stream C will be lower than that of the stream G and the bottom temperature, which can be used for process control as a temperature adjustment.

[0062] The reaction rectification column is also provided with a heating inner coil (not shown in the figure), and the residual monoethyl maleate in the bottom of the reaction rectification column 8 can be reheated by the inner coil, and then the reheated monoethyl maleate is fed into the column for further esterification into diethyl maleate, so as to improve the degree of diesterification.

[0063] The feed amount of the stream B is adjusted, and the circulation and collection ratio of the stream D and the stream E is adjusted, so as to increase the collection ratio as much as possible while meeting the control index requirement. A discharge port is arranged at the top of the reaction column, and the ethanol, diethyl ether and water mixed vapor (stream H) at the top of the column is driven into the vapor permeation membrane system under pressure.

[0064] ​The stream D enters the thin film evaporator 9, the operating temperature of the thin film evaporator 9 is controlled at about 100-110℃, the vacuum degree is above-0.098MPa, the stream D is separated to remove the light component impurities such as water, ethanol and ether in the stream D, and the light component impurities are condensed and collected in the collecting tank 11 through the condenser 10 under the suction of the vacuum pump 112 to form the stream I, the condenser 10 used in the present application is a horizontal condenser. The stream I is pressurized by the ethanol pump 113 to the pipeline connected with the stream H, so that the stream H and the stream I are combined, the stream H and the stream I are driven by the self pressure and suction of the vacuum pump 116 of the steam permeation membrane device 18, first pass through the heat supplement device 17 to vaporize the ethanol, water and ether, the steam permeation membrane device 18 used in the present application is a molecular sieve membrane, the stream H and the stream I enter the pipe in gaseous state, the permeation side pressure is controlled below 2000Pa, at this time, the water molecules are separated to the outside of the membrane pipe through the holes of the molecular sieve permeation membrane, and are stored in the waste water tank 14 after being condensed by the condenser 115.

[0065] The stream H and the stream I after dehydration are condensed and collected in the ethanol collecting tank 20 by the condenser 119 to form the stream J containing a large amount of ethanol and a small amount of ether, the coolant of the condenser 119 is-5 to +10℃ ethylene glycol refrigerant. The stream J is pumped back to the monoester reaction kettle 1 by the ethanol pump 121, first passes through the horizontal condenser 3, at this time, the temperature of the stream J is-5 to +10℃, which can act as the coolant of the horizontal condenser 3 to condense the ether vapor rising from the monoester reaction kettle 1, so that the ether vapor is condensed and collected in the ether collecting tank 4 after passing through the horizontal condenser 3. Referring to Figure 5 , the content of each component in the ether collecting tank 4 is: ethanol 67.62% and ether 32.38%.

[0066] The stream J after passing through the horizontal condenser 3 returns to the monoester reaction kettle 1, in which the ethanol and maleic anhydride undergo ring-opening reaction. The ether in the stream J returns to the monoester reaction kettle 1, is evaporated to the horizontal condenser 3 under the influence of ring-opening exothermic without external heating, is condensed and collected in the ether collecting tank 4, and is separated.

[0067] Importantly, the stream D removes the light component impurities to obtain heavy component substances, the heavy component substances are the crude product mainly containing maleic acid diethyl ester, and the finished product maleic acid diethyl ester is obtained after alkali washing, water washing, dehydration and rectification.

[0068] In summary, the product maleic acid diethyl ester produced by the continuous preparation process of maleic acid diethyl ester in the present application has a product content≥99.0%, and the content of fumaric acid diethyl ester is less than 2%, the conversion rate of maleic anhydride≥99.0%, and the catalyst does not need to be frequently replaced, which realizes the industrial production of maleic acid diethyl ester and has excellent social and economic value.

[0069] The embodiments are only illustrative of the present application, and are not intended to limit the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A continuous production process of diethyl maleate, characterized by, It comprises the following steps: S1: maleic anhydride and first ethanol enter the monoester reactor (1), and the reaction obtains stream A; S2: the stream A enters the diester reactor (5) to continue esterification, and the reaction obtains stream B; S3: the stream B enters the reaction distillation column (8) from the column, and second ethanol enters the reaction distillation column (8) from the bottom of the column; stream H is collected from the top of the column, and stream C is collected from the bottom of the column; S4: the stream C is divided into stream D, stream E and stream F, wherein the stream D enters the thin film evaporator (9) to remove ethanol, water and diethyl ether to obtain diethyl maleate product, the water, ethanol and diethyl ether light component impurities in the stream D are removed, and the stream D is condensed and collected in the collection tank (11) through the condenser (10) under the suction of the vacuum pump (12) to form stream I, the stream I is pressurized by a pump and connected to the stream H in S3 through a pipeline to be transported into the steam permeation membrane device (18) through the pipeline, and the stream E is transported to the reaction distillation column (8) through a pipeline to be recycled; S5: the reaction distillation column (8) is provided with a reboiler (6), and the stream F returns to the bottom of the reaction distillation column (8) after flowing through the reboiler; S6: the stream H and the stream I are treated through the steam permeation membrane device (18) to obtain stream J mainly containing ethanol and diethyl ether, the stream J is condensed and collected, and the temperature of the stream J is relatively low, so the stream J is designed to pass through the horizontal condenser (3) to act as a refrigerant and then enters the monoester reactor (1); S7: the monoester reactor (1) is provided with a horizontal condenser (3), and the diethyl ether component in the stream J is evaporated in the monoester reactor (1) and is condensed and collected in the diethyl ether collection tank (4) through the horizontal condenser (3).

2. The method for continuous production of diethyl maleate according to claim 1, characterized by: The reaction distillation column (8) is provided with a carrier plate loaded with a solid catalyst.

3. The method for continuous production of diethyl maleate according to claim 1, characterized by: The monoester reactor (1) is provided with a stirring device, a temperature rising and falling device and a vertical condenser (2), the temperature of the monoester reactor (1) is controlled to be between 50-80℃, and the temperature of the vertical condenser (2) is controlled to be between 35-45℃.

4. The method for continuous production of diethyl maleate according to claim 1, characterized by: The diester reactor (5) is a fixed bed reactor, the diester reactor (5) is provided with a solid catalyst, the reaction temperature in the diester reactor (5) is controlled to be between 80-130℃, and the reaction pressure is 0.3-1.0 MPa.

5. The method for continuous production of diethyl maleate according to claim 1, characterized by: The reaction distillation column (8) is further provided with a temperature rising and falling device.

6. The method for continuous production of diethyl maleate according to claim 1, characterized by: The steam permeation membrane device (18) is provided with a heat compensator (17) at the front end, the stream I and the stream H are heated through the heat compensator (17), and the temperature of the heat compensator (17) is 99-120℃.

7. The method for continuous production of diethyl maleate according to claim 1, characterized by: The steam permeation membrane device (18) is provided with a refrigerant with a temperature of-5 to +10℃.

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