CN113461521B - Production process system and production method of dialkyl maleate - Google Patents
Production process system and production method of dialkyl maleate Download PDFInfo
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Abstract
The invention relates to a production process system and a method of dialkyl maleate, which comprises an autocatalysis reaction section and a post-esterification reaction section, wherein the post-esterification reaction section comprises a plurality of reaction kettles which are connected in series, the reaction kettles are connected with pipelines for feeding and discharging, valves are arranged on the pipelines, and one or any number of reaction kettles can be off-line from production by controlling the valves. The reaction kettle can lead one or more reaction kettles to be off-line from production through the reasonable design of the pipeline and the valve for replacing the catalyst or overhauling, the catalyst is convenient and quick to replace, and the whole reaction can not be influenced. The content of maleic acid monoalkyl ester in the autocatalytic reaction section is reduced to the maximum, so that the harm to a double esterification catalyst in a post esterification reaction section is reduced to the minimum; on the other hand, after the residual maleic acid monoalkyl ester enters the post-esterification reaction section, the residual maleic acid monoalkyl ester can be completely converted into maleic acid dialkyl ester without too much double-esterification catalyst.
Description
Technical Field
The invention relates to the technical field of heterogeneous catalytic reaction equipment and methods, in particular to a production process system and a production method of dialkyl maleate.
Background
Dimethyl maleate is colorless oily liquid and is an important organic synthesis intermediate. In the production of 1, 4-Butanediol (BDO) and Tetrahydrofuran (THF) as a byproduct from Maleic Anhydride (MAH), the first stage is esterification of Maleic Anhydride (MAH) with C1-C4 lower alkanol (e.g., methanol, ethanol, n-butanol) to produce dialkyl maleate (particularly dimethyl maleate). For example: documents US4795824, WO90/08127, US4751334, WO88/00937 and US4584419 disclose the esterification of maleic anhydride with a lower alkanol as starting material, followed by hydrogenation to obtain 1, 4-butanediol, gamma-butyrolactone, tetrahydrofuran and by-product acetal. Moreover, dialkyl maleates can also be used as plasticizers for polymeric monomers and synthetic resins; also used for preparing insecticide, bactericide, antirust additive, organic solvent, etc.
In the esterification unit, during the current industrial production, firstly maleic anhydride and excessive lower alkanol such as methanol are subjected to exothermic reaction in a tubular pre-esterification reactor to generate monomethyl maleate and part of dialkyl maleate, and methanol and part of generated water are evaporated and removed from the top of the pre-esterification reactor; then the monomethyl maleate and the methanol are further reacted in a post-esterification reactor under the action of a double-esterification catalyst to obtain the dimethyl maleate. The post-esterification reactor is a catalytic distillation reaction tower, a plurality of catalyst trays are arranged in the tower, granular acidic double-esterification catalysts (such as acidic ion exchange resin, solid acid catalyst and the like) are filled in the trays, liquid materials flow from top to bottom while reacting, generated water is continuously separated from the top of the tower to catalyze the double-esterification reaction to be carried out backwards, the concentration of dimethyl maleate is gradually increased from top to bottom, monoalkyl maleate at the bottom of the post-esterification reactor is basically converted into dimethyl maleate, and the conversion rate is more than 99%.
However, since the acidic property of the monoalkyl maleate is strong, the acidic double esterification catalyst in the catalytic distillation reaction tower gradually becomes inactive as the reaction proceeds, and it is necessary to replace the spent catalyst with a fresh catalyst for 1 to 3 weeks. Typically, the post-shutdown esterification reactor is required to replace the catalyst in the column. However, since the reactant stream flows from top to bottom, the catalyst located at the uppermost layer of the post-esterification reactor is deactivated first and then gradually becomes deactivated from top to bottom at different rates depending on the height of the catalyst in the column. If the entire post-esterification reactor is shut down, a portion of the catalyst is not deactivated and does not need to be replaced. To reduce catalyst wastage, the shut-down timing is delayed until more catalyst is deactivated and the catalyst has to be replaced.
In order to solve these problems, researchers have developed various post-esterification reactors that can replace the catalyst on-line while producing it. Other plant arrangements for removing the catalyst without shutting down the reactor are known from the documents US5510089, US5198196, US133942, US 6036848. However, the online catalyst replacement also causes unstable operation, and the catalyst on the reaction tower plate is carried to the upper tower plate by the gas phase or carried to the lower tower plate by the liquid phase, thereby causing uneven distribution of the catalyst and influencing the reaction. Document CN201280006775.9 discloses a device for heterogeneous catalytic reaction, which employs a liquid transfer tank arranged outside each section of catalyst tray of a post-esterification reactor, and bypasses the tray needing to replace the catalyst through pipes arranged at intervals; at the same time, the catalyst to be replaced is sent to the filter separator together with the flow on the tray, and the separated liquid and fresh catalyst are returned to the tray. However, such on-line catalyst replacement requires a large liquid flow to push the spent catalyst out of the tray and into the filter, which can cause a change in the pressure distribution within the column; moreover, the catalyst flowing into the tray under the driving of the pump is unevenly distributed, so that the loss of the catalyst caused by abrasion is also increased, the catalyst becomes powder and leaks out of the filter, and the consumption of the catalyst is greatly increased; moreover, a pipeline bypassing one or more catalyst trays needs to be arranged under the liquid transfer tank of each section of catalyst tray, so that the quantity of catalyst trays which are replaced at the same time is limited, the pipelines of the post-esterification reactor are complicated and disordered, and the convenience of operation of workers is influenced.
Disclosure of Invention
The present invention aims to solve the above technical problems and disadvantages, and to provide a production process system and a production method for dialkyl maleate.
In order to solve the technical problems, the invention adopts the technical scheme that: a production process system of dialkyl maleate comprises an autocatalysis reaction section and a post-esterification reaction section, wherein the post-esterification reaction section comprises a plurality of reaction kettles which are connected in series, the reaction kettles are connected with pipelines for feeding and discharging, valves are arranged on the pipelines, and one or any of the reaction kettles can be off-line from production by controlling the valves.
As a further optimization of the production process system of dialkyl maleate of the present invention, the post-esterification reaction section comprises three reaction kettles connected in series, namely reaction kettle R1, reaction kettle R2 and reaction kettle R3, and the material flow of the post-esterification reaction section comprises an autocatalytic product material flow, a low carbon alcohol material flow, a new catalyst material flow and a waste catalyst material flow;
the autocatalytic product stream is conveyed along an autocatalytic product line comprising a main conduit 11 and a branch conduit L1 feeding reactor R1;
the low-carbon alcohol material flow is conveyed along a low-carbon alcohol pipeline, and the low-carbon alcohol pipeline comprises a main pipeline 12 and branch pipelines L4, L5 and L6 which respectively supply materials to a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3;
the discharge end of the branch pipeline L4 is connected to the main pipeline 11 at the upstream of the branch pipeline L1; the branch pipeline L5, the reaction material pipeline 13 of the reaction kettle R1 and the feeding pipe of the reaction kettle R2 are connected through a three-way joint T2, and the branch pipeline L5 and the main pipeline 11 are in cross connection through a four-way joint T1; the branch pipe L6, the reaction material pipeline 14 of the reaction kettle R2 and the feeding pipe of the reaction kettle R3 are connected through a three-way joint T3, and the branch pipe L6 and the main pipeline 11 are in cross connection through a three-way joint T4;
the reaction material pipeline 14 of the reaction kettle R2 is also connected with an auxiliary discharge pipe L10 through a tee joint T5;
the new catalyst stream is conveyed along a new catalyst line comprising a main line 15 and branch lines L7, L8 and L9 feeding reactor R1, reactor R2 and reactor R3, respectively;
the spent catalyst stream is conveyed along a spent catalyst line comprising a main line 16 and branch lines discharging from reactor R1, reactor R2 and reactor R3, respectively;
the feeding pipes of the reaction kettles R1, R2 and R3 are respectively provided with a control valve V1, a control valve V2 and a control valve V3; a control valve V4 is arranged on the main pipeline 11 at the upstream of the four-way joint T1; a control valve V5 is arranged on a pipeline of the main pipeline 11 between the four-way joint T1 and the three-way valve T4; control valves V7 and V8 are respectively arranged on reaction material pipelines of the reaction kettles R1 and R2.
As a further optimization of the production process system of the dialkyl maleate, the top of each reaction kettle comprises a rectifying section, and an outlet pipe at the top of the rectifying section is connected with a low carbon alcohol separation tower.
As a further optimization of the production process system of the dialkyl maleate, the autocatalytic reaction section comprises N reactors connected in series, and the shell pass or jacket of each reactor is a preheated low carbon alcohol pipeline.
As a further optimization of the production process system of dialkyl maleate according to the present invention, the N ═ 2, i.e., the autocatalytic reaction section comprises two reactors in series, a first reactor and a second reactor respectively.
As a further optimization of the production process system of the dialkyl maleate provided by the invention, the first reactor is a tubular reactor or a kettle reactor, and the second reactor is a tubular reactor or a fixed bed reactor.
As a further optimization of the production process system of the dialkyl maleate, the low-carbon alcohol separation tower is a reduced-pressure rectifying tower.
A method for producing dialkyl maleate, comprising the steps of:
(1) respectively feeding the molten maleic anhydride and the molten low-carbon alcohol into an autocatalytic reaction section, and carrying out pre-esterification reaction by N reactors connected in series in the autocatalytic reaction section to obtain an autocatalytic material flow;
(2) feeding the autocatalysis material flow flowing out of the Nth reactor and the heated low-carbon alcohol into reaction kettles connected in series at a post-esterification reaction section together for heterogeneous catalytic reaction, feeding a new catalyst into the reaction kettles through a new catalyst inlet arranged at the lower part of each reaction kettle, and discharging reaction products through a reaction material outlet; through pipelines and valves connected among the reaction kettles, one or more reaction kettles are taken out from production in an off-line mode to carry out catalyst replacement or equipment maintenance; the product of the rectification section of each reaction kettle enters a low-carbon alcohol separation tower through a top outlet pipe, then the low-carbon alcohol separation tower separates the low-carbon alcohol from water by reducing the pressure, and the obtained low-carbon alcohol is used as a raw material and returns to the autocatalysis reaction section or the post-esterification reaction section to continue to participate in the reaction.
As a further optimization of the production method of dialkyl maleate, in the N reactor in the step (1), the concentration of monoalkyl maleate and dialkyl maleate reaches reaction balance, the reaction heat in each reactor is taken away by the heat exchange of the low carbon alcohol flowing through the shell side or the jacket of the reactor, and the low carbon alcohol is heated and then used as a raw material for subsequent reaction.
As a further optimization of the production method of the dialkyl maleate, the low-carbon alcohol refers to one of alkyl alcohols with 1-4 carbon atoms.
The invention has the following beneficial effects:
in the production method, the maleic acid monoalkyl ester is converted into maleic acid dialkyl ester as much as possible in the autocatalytic reaction section, the content of the maleic acid monoalkyl ester is reduced to the maximum, and on one hand, the harm to a double esterification catalyst in a later esterification reaction section is reduced to the minimum; on the other hand, after the residual maleic acid monoalkyl ester enters the post-esterification reaction section, the residual maleic acid monoalkyl ester can be completely converted into the maleic acid dialkyl ester without needing too many stages of double-esterification catalysts.
The post-esterification reaction section can be directly a plurality of reaction kettles with rectification sections, and the rectification sections of the double-esterification catalyst are only used for separating water generated in the reaction kettles, so that the purpose can be achieved only by filling common ceramic fillers, the reaction difficulty is reduced, and the operation is simple and convenient.
And thirdly, the reaction kettle can be taken out from production line by one or more reaction kettles through the reasonable design of pipelines and valves, so that the catalyst can be replaced or maintained conveniently and quickly, and the whole reaction can not be influenced.
Drawings
FIG. 1 is a schematic view of a production process of an autocatalytic reaction section in example 1 of the present invention;
FIG. 2 is a schematic view of a reaction vessel of a post-esterification reaction zone in example 1 of the present invention;
FIG. 3 is a schematic view of the production process in the post-esterification reaction zone in example 1 of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the figures are for clarity of explanation only and that other items of equipment may be required in an industrial setting, for example: the device comprises a reflux liquid reservoir, a material flow pump, a vacuum pump, a temperature sensor, a pressure reducing valve, a control valve, a flow controller, a collecting tank, a storage tank and the like. The provision of such auxiliary items of equipment forms no part of the present invention and the arrangement should be selected in accordance with conventional chemical practice.
Example 1
A production process system of dialkyl maleate comprises an autocatalysis reaction section and a post-esterification reaction section, wherein the post-esterification reaction section comprises a plurality of reaction kettles which are connected in series, the reaction kettles are connected with pipelines for feeding and discharging, valves are arranged on the pipelines, and one or any of the reaction kettles can be off-line from production by controlling the valves.
The post-esterification reaction section comprises three reaction kettles which are connected in series, namely a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3, and the material flow of the post-esterification reaction section comprises an autocatalysis product material flow, a low carbon alcohol material flow, a new catalyst material flow and a waste catalyst material flow;
the autocatalytic product stream is conveyed along an autocatalytic product line comprising a main conduit 11 and a branch conduit L1 feeding reactor R1; the low-carbon alcohol material flow is conveyed along a low-carbon alcohol pipeline, and the low-carbon alcohol pipeline comprises a main pipeline 12 and branch pipelines L4, L5 and L6 which respectively supply materials to a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3;
the discharge end of the branch pipeline L4 is connected to the main pipeline 11 at the upstream of the branch pipeline L1; the branch pipeline L5, the reaction material pipeline 13 of the reaction kettle R1 and the feeding pipe of the reaction kettle R2 are connected through a three-way joint T2, and the branch pipeline L5 and the main pipeline 11 are in cross connection through a four-way joint T1; the branch pipe L6, the reaction material pipeline 14 of the reaction kettle R2 and the feeding pipe of the reaction kettle R3 are connected through a three-way joint T3, and the branch pipe L6 and the main pipeline 11 are in cross connection through a three-way joint T4;
the reaction material pipeline 14 of the reaction kettle R2 is also connected with an auxiliary discharge pipe L10 through a tee joint T5;
the new catalyst stream is conveyed along a new catalyst pipeline, and the new catalyst pipeline comprises a main pipeline 15 and branch pipelines L7, L8 and L9 which respectively supply materials to a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3;
the waste catalyst material flow is conveyed along a waste catalyst pipeline, and the waste catalyst pipeline comprises a main pipeline 16 and branch pipelines respectively discharging from a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3;
control valves V1, V2 and V3 are respectively arranged on feed pipes of the reaction kettles R1, R2 and R3; a control valve V4 is arranged on the main pipeline 11 at the upstream of the four-way joint T1; a control valve V5 is arranged on a pipeline of the main pipeline 11 between the four-way joint T1 and the three-way valve T4; control valves V7 and V8 are respectively arranged on reaction material pipelines of the reaction kettles R1 and R2; control valves V6, V9 and V13 are respectively arranged on new catalyst feeding pipes of the reaction kettles R1, R2 and R3; control valves V10, V11 and V12 are respectively arranged on the waste catalyst discharging pipes of the reaction kettles R1, R2 and R3.
The top of each reaction kettle comprises a rectifying section, and an outlet pipe at the top of the rectifying section is connected with a low-carbon alcohol separation tower. The low-carbon alcohol separation tower is a decompression rectifying tower.
The autocatalysis reaction section comprises N reactors connected in series, and the shell side or the jacket of each reactor is a preheating low-carbon alcohol pipeline. The self-catalytic reaction section comprises two reactors connected in series, namely a first reactor and a second reactor. The first reactor is a tubular reactor or a kettle reactor, and the second reactor is a tubular reactor or a fixed bed reactor.
A method for producing dialkyl maleate, taking dimethyl maleate as an example and methanol as a lower alcohol, comprises the following steps:
(1) respectively feeding molten maleic anhydride and methanol into an autocatalytic reaction section which is a first reactor A1 and a second reactor A2 which are connected in series; the first reactor A1 is a tubular reactor, and the second reactor A2 is a fixed bed reactor;
in the first reactor a1, maleic anhydride and methanol were reacted in the tube side, with complete conversion of maleic anhydride to monomethyl maleate and about 2% of monomethyl maleate continuing to dimethyl maleate; the molar ratio of methanol to maleic anhydride was 1.10: 1, the reaction pressure is 0.9MPa, and the reaction temperature is not more than 120 ℃; because the reaction of the maleic anhydride and the methanol is a strong exothermic reaction, the heat released by the reaction can be used for heating the methanol required by the second reactor A2, and the methanol at normal temperature is introduced into the shell side of the first reactor A1 to reduce the temperature;
in the second reactor A2, methanol heated to 100-120 ℃ is merged with the material flow sent from the first reactor A1, and monomethyl maleate continuously reacts with the methanol to generate dimethyl maleate; the reaction temperature is 110-120 ℃, and the reaction pressure is as follows: 0.9MPa, the molar ratio of methanol to the initial maleic anhydride is 7:1, and the material retention time is 9 hours; a water extraction pipeline is arranged on the second reactor A2, and an azeotrope of water and the low-carbon alkanol is distilled and separated out in time to push the reaction to be carried out; finally, the concentration of the monomethyl maleate and the dimethyl maleate reach the reaction equilibrium, and about 85 percent of the monomethyl maleate is converted into the dimethyl maleate; and (3) sending the azeotrope of the methanol and the water separated from the reactor to a methanol separation tower to separate the methanol from the water through vacuum rectification, and returning the obtained methanol to a methanol storage tank to serve as a reaction raw material.
(2) Sending the autocatalysis product flow flowing out of the second reactor into a post-esterification reaction section for carrying out heterogeneous catalytic reaction; the post-esterification reaction section consists of a plurality of reaction kettles which are connected in series and provided with rectification sections, and the double-esterification catalyst is arranged in the reaction kettles;
the upper part of the reaction kettle with the rectifying section is provided with a catalyst inlet and a reaction material inlet, the bottom of the reaction kettle is respectively provided with a catalyst outlet and a reaction material outlet, and the top of the reaction kettle is provided with a rectifying section of methanol and water.
The material inlet pipelines of the reaction kettles R1, R2 and R3 are respectively provided with a R1 feed pipeline L1, a R2 feed pipeline L2 and a R3 feed pipeline L3 which are connected with the material outlet pipe of the second reactor, and the preheating low-carbon alcohol pipelines L4, L5 and L6 are also respectively connected with the feed pipelines L1, L2 and L3; the lower part of each reaction kettle is provided with a new catalyst inlet pipe L7, a new catalyst inlet pipe L8 and a new catalyst inlet pipe L9, and the new catalyst inlet pipes are connected in series and then connected with a new catalyst storage tank; the bottom of each reaction kettle is provided with a waste catalyst outlet valve V10, a waste catalyst outlet valve V11 and a waste catalyst outlet valve V12 which are connected in series through a pipeline and then are connected with a waste catalyst storage tank; an outlet pipe at the top of the rectifying section of the reaction kettle is connected in series and then is connected with a low-carbon alcohol separation tower;
r1 feed valve V1, R2 feed valve V2 and R3 feed valve V3 are respectively arranged on the pipelines L1, L2 and L3;
the esterification reactor is connected in series by 3 reaction kettles as an example: stream 11 from the autocatalytic reaction stage is passed from feed line L1 through valve V1 into first reactor R1 together with methanol 12 make-up from preheated lower alcohol line L4; after reacting for a period of time, the liquid material 13 is sent out from a valve V7 and enters a second reaction kettle R2 together with methanol 12 supplemented from a preheated low-carbon alcohol pipeline L5; after a period of reaction time, liquid feed 14 is fed out through valve V8 and into third reactor R3 along with additional methanol 12 from preheated lower alcohol line L6.
If the first reactor R1 needs to be replaced, valves V1 and V7 are closed, and valve V4 is opened; stream 11 from the autocatalytic reaction stage bypasses first reactor R1 and enters first reactor R2 along with make-up methanol 12 from feed line L2. Spent catalyst is withdrawn from the bottom of first reactor R1 through valve V10 and fresh catalyst is fed to first reactor R1 through valve V6.
If the catalyst needs to be replaced in the second reaction kettle R2, closing valves V2, V4 and V8, and opening a valve V5; stream 13 from first reactor R2 bypasses second reactor R2 and enters third reactor R3 from feed line L3 along with make-up methanol 12. The waste catalyst is discharged from the bottom valve V11 of the second reaction vessel R2, and the new catalyst is sent into the second reaction vessel R2 through the valve V9, and so on.
If the first reaction kettle R1 and the second reaction kettle R2 need to replace the catalyst at the same time, valves V1, V2, V7 and V8 are closed, and valves V4 and V5 are opened; stream 11 from the autocatalytic reaction section bypasses first reactor R1 and second reactor R2 and enters third reactor R3 along with fresh make-up methanol 12 from feed line L3.
While the invention has been described in detail with respect to the embodiment of 3 reactors, it is within the scope of the invention to modify the design of the lines and valves in any way that increases or decreases the number of reactors in accordance with the principles of the invention. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (8)
1. A production process system of dialkyl maleate comprises an autocatalysis reaction section and a post-esterification reaction section, and is characterized in that: the post-esterification reaction section comprises at least three reaction kettles which are connected in series, namely a reaction kettle R1, a reaction kettle R2 and a reaction kettle R3, and the material flow of the post-esterification reaction section comprises an autocatalysis product material flow, a low carbon alcohol material flow, a new catalyst material flow and a waste catalyst material flow; each reaction kettle is connected with a pipeline for feeding and discharging, the pipelines are provided with valves, and one or more reaction kettles can be taken off line from production by controlling the valves;
the autocatalytic product stream is carried along an autocatalytic product line comprising a main conduit 11 and a branch conduit L1 feeding the reactor R1;
the low-carbon alcohol material flow is conveyed along a low-carbon alcohol pipeline, and the low-carbon alcohol pipeline comprises a main pipeline 12, and a branch pipeline L4, a branch pipeline L5 and a branch pipeline L6 which respectively supply materials to the reaction kettle R1, the reaction kettle R2 and the reaction kettle R3;
the discharge end of the branch pipeline L4 is connected to the main pipeline 11 upstream of the branch pipeline L1; the branch pipeline L5, the reaction material pipeline 13 of the reaction kettle R1 and the feeding pipe of the reaction kettle R2 are connected through a three-way joint T2, and the branch pipeline L5 and the main pipeline 11 are in cross connection through a four-way joint T1; the branch pipe L6, the reaction material pipeline 14 of the reaction kettle R2 and the feeding pipe of the reaction kettle R3 are connected through a three-way joint T3, and the branch pipe L6 and the main pipeline 11 are in cross connection through a three-way joint T4;
the reaction material pipeline 14 of the reaction kettle R2 is also connected with an auxiliary discharge pipe L10 through a tee joint T5;
the new catalyst material flow is conveyed along a new catalyst pipeline, and the new catalyst pipeline comprises a main pipeline 15, and a branch pipeline L7, a branch pipeline L8 and a branch pipeline L9 which respectively supply materials to the reaction kettle R1, the reaction kettle R2 and the reaction kettle R3;
the waste catalyst material flow is conveyed along a waste catalyst pipeline which comprises a main pipeline 16 and branch pipelines respectively discharging from the reaction kettle R1, the reaction kettle R2 and the reaction kettle R3;
the feeding pipes of the reaction kettle R1, the reaction kettle R2 and the reaction kettle R3 are respectively provided with a control valve V1, a control valve V2 and a control valve V3; the main pipeline 11 is provided with a control valve V4 at the upstream of the four-way joint T1; a control valve V5 is arranged on a pipeline of the main pipeline 11 between the four-way joint T1 and the three-way valve T4; and the reaction material pipelines of the reaction kettle R1 and the reaction kettle R2 are respectively provided with a control valve V7 and a control valve V8.
2. The dialkyl maleate production process system of claim 1, wherein: the top of each reaction kettle comprises a rectifying section, and an outlet pipe at the top of the rectifying section is connected with a low-carbon alcohol separation tower.
3. The dialkyl maleate production process system of claim 2, wherein: the low-carbon alcohol separation tower is a decompression rectifying tower.
4. The dialkyl maleate production process system of claim 1, wherein: the autocatalytic reaction section comprises 2 reactors connected in series, namely a first reactor and a second reactor; the shell side or the jacket of each reactor is a preheated low carbon alcohol pipeline.
5. The dialkyl maleate production process system of claim 4, wherein: the first reactor is a tubular reactor or a kettle reactor, and the second reactor is a tubular reactor or a fixed bed reactor.
6. A method for producing dialkyl maleate, which is characterized in that: the method comprises the following steps:
(1) respectively feeding molten maleic anhydride and low-carbon alcohol into an autocatalysis reaction section, and carrying out pre-esterification reaction through 2 reactors connected in series in the autocatalysis reaction section to obtain an autocatalysis product material flow;
(2) feeding the autocatalysis product material flow flowing out of the second reactor and the heated low-carbon alcohol into reaction kettles connected in series at the post-esterification reaction section together for heterogeneous catalytic reaction, feeding a new catalyst into the reaction kettles through a new catalyst inlet arranged at the lower part of each reaction kettle, and discharging the reaction products through a reaction material outlet; controlling pipelines and valves connected among the reaction kettles to enable one or any of the reaction kettles to be offline in production so as to replace the catalyst or overhaul equipment; the product of the rectification section of each reaction kettle enters a low-carbon alcohol separation tower through a top outlet pipe, then the low-carbon alcohol separation tower separates the low-carbon alcohol from water by reducing the pressure, and the obtained low-carbon alcohol is used as a raw material and returns to the autocatalysis reaction section or the post-esterification reaction section to continuously participate in the reaction.
7. The process for producing dialkyl maleate according to claim 6 wherein: in the second reactor in the step (1), the concentration of the maleic acid monoalkyl ester and the maleic acid dialkyl ester reaches reaction balance, the reaction heat in each reactor is taken away by the heat exchange of the low-carbon alcohol flowing through the shell side or the jacket of the reactor, and the low-carbon alcohol is heated and then used as the raw material of the subsequent reaction.
8. The process for producing a dialkyl maleate according to claim 6, wherein: the lower alcohol is one of alkyl alcohols with 1-4 carbon atoms.
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| CN103360253A (en) * | 2012-04-01 | 2013-10-23 | 中国石油化工股份有限公司 | Method for producing dimethyl maleate |
| WO2017064470A1 (en) * | 2015-10-13 | 2017-04-20 | Johnson Matthey Davy Technologies Limited | Process for the co-production of dialkyl maleate and dialkyl succinate |
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| CN101314564A (en) * | 2007-06-01 | 2008-12-03 | 上海焦化有限公司 | Preparation of maleic acid di-methyl ester |
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| CN103360253A (en) * | 2012-04-01 | 2013-10-23 | 中国石油化工股份有限公司 | Method for producing dimethyl maleate |
| WO2017064470A1 (en) * | 2015-10-13 | 2017-04-20 | Johnson Matthey Davy Technologies Limited | Process for the co-production of dialkyl maleate and dialkyl succinate |
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