Production device and production method of dimethyl adipate

Abstract

The invention discloses a production device and a production method of dimethyl adipate, and belongs to the technical field of organic chemical synthesis. According to the scheme, efficient conversion of part of adipic acid is realized in the pre-reactor, so that the reaction load of a subsequent catalytic distillation tower is reduced; cyclohexane is adopted as an azeotropic water-carrying agent in a catalytic distillation tower, water generated by reaction is removed in real time through azeotropic distillation, the equilibrium limitation of esterification reaction is broken, complete conversion of adipic acid is realized, and the reaction efficiency is remarkably improved. According to the method, methanol and cyclopentane are efficiently separated through the washing step, cyclic utilization of cyclopentane is achieved, and raw material consumption is greatly reduced; meanwhile, resource utilization of methanol is achieved through the methanol recovery system, and waste emission is reduced. The method can effectively reduce energy consumption and production cost, improves product quality, and solves the problems of easy catalyst deactivation, severe equipment corrosion, high three-waste treatment cost and the like in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic chemical synthesis, in particular to a production device and method of dimethyl adipate. BACKGROUND

[0002] Dimethyl adipate (CAS No. 627-93-0) is an important aliphatic dibasic acid ester, with the chemical formula of C8H14O4. It is a colorless transparent liquid at room temperature, with low volatility and good solubility (soluble in alcohol and ether, insoluble in water). As a high-efficiency cold-resistant plasticizer, it can significantly improve the low-temperature flexibility of polymers such as PVC, and is widely used in high-grade coatings, synthetic resins and ink solvent fields. It is also a key chemical intermediate, which can be hydrogenated to produce 1,6-hexanediol, which is an important raw material for polyesters and polyurethanes. Compared with traditional o-phenyl plasticizers, this compound has excellent environmental performance and light and thermal stability, which meets the development trend of green chemistry.

[0003] The existing technology mainly has the following problems in the synthesis of dimethyl adipate: the traditional sulfuric acid catalyst process leads to equipment corrosion and three-waste pollution; the intermittent operation has low efficiency and insufficient conversion rate; the solid acid catalyst needs to be frequently replaced and the pre-esterification step is complex; the reaction heat is not fully utilized, resulting in high energy consumption. In view of these problems, CN102442905B proposes a continuous esterification process, which uses a two-stage reaction system of catalyst-free pre-esterification combined with a catalytic distillation column (strong acid resin catalyst), realizes continuous feeding through the inner member of the tubular reactor, and utilizes the reaction heat to exchange with the raw materials to save energy. However, it has obvious shortcomings: the pre-esterification conversion rate is only 95.6%, which leads to the need for subsequent treatment of residual monomethyl ester; the energy consumption of gas phase condensation at the top of the tower is still high. CN109748790A further optimizes the process flow, which uses a tubular shell type primary reactor combined with a plate type catalytic distillation column, and eliminates the condensation step by directly passing the gas phase at the top of the tower to the methanol recovery tower. The product purity of this process reaches 99.5% and the acid value is ≤0.5 mgKOH / g, but the molten feed is easy to block the tubular shell reactor, and the space-time rate of 0.2-0.6 h-1 limits the production capacity flexibility. Although the two patents have made progress in continuous production and energy saving, they are limited by the service life of the catalyst and the adaptability of the equipment.

[0004] Therefore, it is an urgent problem for those skilled in the art to provide a high-efficiency, energy-saving and environmentally friendly production device and method for continuously preparing dimethyl adipate. SUMMARY

[0005] The present application overcomes the technical defects of high energy consumption, insufficient conversion rate and poor environmental performance in the existing dimethyl adipate production process, and provides a high-efficiency, energy-saving and environmentally friendly production device and method for producing dimethyl adipate.

[0006] To this end, one object of the present application is to provide a device for producing dimethyl adipate, comprising a monomethyl ester reactor, a dimethyl ester reactor, a catalytic distillation deep reactor, a methanol extraction column and a methanol recovery column;

[0007] Wherein the monomethyl ester reactor, the dimethyl ester reactor, the catalytic distillation deep reactor, the methanol extraction column and the methanol recovery column are sequentially communicated.

[0008] The bottom feed inlet of the monomethyl ester reactor is communicated with the first mixer through the monomethyl ester reactor feed pipe, and the feed inlets of the first mixer are communicated with the adipic acid feed pipe and the methanol feed pipe, respectively.

[0009] The top discharge outlet of the monomethyl ester reactor is communicated with the bottom feed inlet of the dimethyl ester reactor through the monomethyl ester reactor discharge pipe and the dimethyl ester reactor feed pipe, and a second mixer is arranged between the monomethyl ester reactor discharge pipe and the dimethyl ester reactor feed pipe, and the feed inlet of the second mixer is further connected with a first supplementary methanol tank.

[0010] The top discharge outlet of the dimethyl ester reactor is communicated with the upper end feed inlet of the catalytic distillation deep reactor through the dimethyl ester reactor discharge pipe, and the lower end feed inlet of the catalytic distillation deep reactor is connected with a second supplementary methanol tank; the lower end discharge outlet of the catalytic distillation deep reactor is discharged through a pipe to produce dimethyl adipate.

[0011] The upper end discharge outlet of the catalytic distillation deep reactor is communicated with the lower end feed inlet of the methanol extraction column through the catalytic distillation column discharge pipe.

[0012] The bottom discharge outlet of the methanol extraction column is communicated with the feed inlet of the methanol recovery column through the methanol water pipe.

[0013] Further, the upper end discharge outlet of the methanol extraction column is communicated with a third mixer through a circulating cyclohexane pipe, the discharge outlet of the third mixer is communicated with the lower end feed inlet of the catalytic distillation deep reactor through the catalytic distillation column cyclohexane feed pipe, and the feed inlet of the third mixer is further connected with a supplementary cyclohexane tank.

[0014] Further, the bottom discharge outlet of the methanol recovery column is communicated with the upper end feed inlet of the methanol extraction column through the extraction water pipe.

[0015] Further, the upper end discharge outlet of the methanol recovery column is discharged to recover methanol.

[0016] The present application realizes the efficient conversion of part of adipic acid in the pre-reactor, reduces the reaction load of the subsequent catalytic distillation column, and then uses cyclohexane as an azeotropic water carrying agent in the catalytic distillation column to remove the generated water in real time through azeotropic distillation, breaks the esterification reaction balance limit, realizes the complete conversion of adipic acid, and significantly improves the reaction efficiency. The present application efficiently separates methanol and cyclopentane through a water washing step, realizes the recycling of cyclopentane, greatly reduces the raw material consumption, and realizes the resource utilization of methanol through a methanol recovery system, reduces waste emissions, and meets the development requirements of green chemical industry. In addition, the present process optimizes the reaction conditions and equipment configuration, effectively reduces the energy consumption and production cost, improves the product quality, provides an economic, efficient and environment-friendly technical path for industrial production, and solves a series of problems such as catalyst deactivation, serious equipment corrosion and high treatment cost of three wastes in the prior art.

[0017] The present application also provides a method for producing dimethyl adipate by using the above device, comprising the following steps:

[0018] (1) Adipic acid and methanol are mixed and then fed into a monomethyl ester reactor, and adipic acid generates monomethyl adipate in the monomethyl ester reactor;

[0019] (2) The outlet material of the monomethyl ester reactor and the supplementary methanol are mixed and then fed into a dimethyl ester reactor, and monomethyl adipate is converted into dimethyl adipate in the dimethyl ester reactor;

[0020] (3) The product is fed into the upper part of the reaction section of the catalytic distillation deep reactor through the outlet of the dimethyl ester reactor, supplementary methanol and cyclohexane are fed into the lower part of the reaction section of the catalytic distillation deep reactor, the separation of methanol and ester is completed in the stripping section of the catalytic distillation deep reactor, the methanol, cyclohexane and generated water on the top of the tower are fed into a methanol water washing tower, the cyclohexane on the top of the tower is recycled, the water containing methanol in the tower kettle is fed into a methanol recovery tank to recover methanol and then recycled, in the reaction section, the monomethyl ester and the ascending methanol are contacted and react under the action of the catalyst, the unreacted monomethyl ester is converted into dimethyl adipate and flows out from the tower kettle, and the generated water is carried out of the reaction system by azeotropy with cyclohexane.

[0021] Further, the reaction temperature of the monomethyl ester reactor is 70-90℃, the reaction pressure is 0.6-0.8 MPa, and the molar ratio of methanol to adipic acid is 1.1-1.2:1.

[0022] Further, the reaction temperature of the dimethyl ester reactor is 80-100℃, the reaction pressure is 0.6-0.8 MPa, and the molar ratio of supplementary methanol to original feed adipic acid is 1.0-2.0:1.

[0023] Further, the catalytic distillation deep reactor has a top temperature of 70-80 DEG C, a reaction pressure of 0.1-0.2 MPa, a molar ratio of the supplementary methanol to the original adipic acid of 0.5-1.0:1, and a reflux ratio of 1-2:1.

[0024] The molar ratio of the supplementary cyclohexane to the original adipic acid is 20-30:1.

[0025] Further, the water-oil mass ratio in the methanol water washing tower is 5-10:1.

[0026] The methanol recovery tower has a top temperature of 60-80 DEG C, a reaction pressure of normal pressure-0.3 MPa, and a reflux ratio of 5-10:1.

[0027] Further, the reaction sections of the monomethyl ester reactor, the dimethyl ester reactor and the catalytic distillation deep reactor are all filled with macroporous strong acid cation resin catalysts.

[0028] The catalytic distillation deep reactor comprises a rectification section, a reaction section and a stripping section from top to bottom, wherein the rectification section has 20-30 theoretical plates; the catalysts in the reaction section are divided into 10-18 sections, each section has a plate in the middle and has 2 theoretical plates; and the stripping section has 10-20 theoretical plates.

[0029] The present application has the following advantages:

[0030] The present application provides a kind of high efficiency energy saving, green and environmental protection's continuous preparation dimethyl adipate device and method, the present application passes through the multi-stage collaborative design of monomethyl ester reactor, dimethyl ester reactor and catalytic distillation deep reactor, first, adipic acid is converted into monomethyl ester, then monomethyl ester is efficiently converted into dimethyl ester, finally, in catalytic distillation deep reactor, water is removed by cyclohexane azeotrope to achieve reaction equilibrium breakthrough, so that the conversion rate is increased to >99.5%.The present application innovatively uses segmented catalyst loading combined with rectification separation, and through water washing tower and methanol recovery tower, 100% cyclohexane recycling and methanol recovery rate >99% are realized, compared with traditional process, energy consumption is reduced by more than 30%, waste acid discharge is completely eliminated, product purity is ≥99.5%, and the problems of catalyst deactivation, equipment corrosion and three waste treatment are solved. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without creative labor.

[0032] Figure 1A production device structure schematic diagram of dimethyl adipate provided by the present application.

[0033] In the drawings, the structure represented by each reference numeral is listed as follows: 1.

[0034] 1 - monomethyl ester reactor, 2 - dimethyl ester reactor, 3 - catalytic distillation deep reactor 4 - methanol extraction column 5 - methanol recovery column, 6 - first mixer 7 - second mixer, 8 - adipic acid feed pipe, 9 - methanol feed pipe, 10 - monomethyl ester reactor feed pipe, 11 - monomethyl ester reactor discharge pipe, 12 - pipe, 13 - first supplementary methanol tank, 14 - dimethyl ester reactor feed pipe, 15 - dimethyl ester reactor discharge pipe, 16 - second supplementary methanol tank, 17 - third mixer, 18 - supplementary cyclohexane tank, 19 - catalytic distillation column cyclohexane feed pipe, 20 - catalytic distillation column discharge pipe, 21 - extraction water pipe, 22 - methanol water g pipe, 23 - circulating cyclohexane pipe, 24 - recovered methanol. DETAILED DESCRIPTION

[0035] The embodiments of the present application are described in detail below with reference to the accompanying drawings. Examples of the embodiments are shown in the drawings, in which the same or similar components are denoted by the same or similar reference numerals throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0036] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0037] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0038] In the present application, unless specifically defined and limited otherwise, the terms "mounting", "connecting", "connecting", "fixing" and the like should be broadly interpreted, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] In the present application, unless specifically defined and limited otherwise, the first feature "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "above" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0040] Embodiment 1

[0041] A production device of dimethyl adipate, comprising a monomethyl ester reactor 1, a dimethyl ester reactor 2, a catalytic distillation deep reactor 3, a methanol extraction tower 4 and a methanol recovery tower 5;

[0042] The monomethyl ester reactor 1, the dimethyl ester reactor 2, the catalytic distillation deep reactor 3, the methanol extraction tower 4 and the methanol recovery tower 5 are sequentially communicated;

[0043] The bottom inlet of the monomethyl ester reactor 1 is communicated with the first mixer 6 through the monomethyl ester reactor feed pipe 10, and the inlet of the first mixer 6 is communicated with the adipic acid feed pipe 8 and the methanol feed pipe 9, respectively;

[0044] The top outlet of the monomethyl ester reactor 1 is communicated with the bottom inlet of the dimethyl ester reactor 2 through the dimethyl ester reactor feed pipe 14 of the dimethyl ester reactor outflow pipe 11, and the second mixer 7 is arranged between the dimethyl ester reactor outflow pipe 11 and the dimethyl ester reactor feed pipe 14, and the inlet of the second mixer 7 is also connected with the first supplementary methanol tank 13;

[0045] The top outlet of the dimethyl ester reactor 2 is communicated with the upper end inlet of the catalytic distillation deep reactor 3 through the dimethyl ester reactor outflow pipe 15, and the lower end inlet of the catalytic distillation deep reactor 3 is connected with the second supplementary methanol tank 16; the lower end outlet of the catalytic distillation deep reactor 3 is discharged through the pipeline 12 to produce dimethyl adipate;

[0046] The upper end outlet of the catalytic distillation deep reactor 3 is communicated with the lower end inlet of the methanol extraction column 4 through a catalytic distillation column outlet pipe 20;

[0047] The bottom outlet of the methanol extraction column 4 is communicated with the inlet of the methanol recovery column 5 through a methanol water pipe 22.

[0048] In some embodiments, the upper end outlet of the methanol extraction column 4 is communicated with the third mixer 17 through a circulating cyclohexane pipe 23, the outlet of the third mixer 17 is communicated with the lower end inlet of the catalytic distillation deep reactor 3 through a catalytic distillation column cyclohexane inlet pipe 19, and the inlet of the third mixer 17 is also connected with a supplementary cyclohexane tank 18.

[0049] In some embodiments, the bottom outlet of the methanol recovery column 5 is communicated with the upper end inlet of the methanol extraction column 4 through an extraction water pipe 21.

[0050] In some other embodiments, the upper end outlet of the methanol recovery column 5 discharges the recovered methanol 24.

[0051] Embodiment 2

[0052] The device described in Embodiment 1 is used, wherein the operating conditions of the monomethyl ester reactor are: reaction temperature 70℃, reaction pressure 0.6MPa, and the molar ratio of methanol to the feedstock adipic acid is 1.1:1.

[0053] The operating conditions of the dimethyl ester reactor are: reaction temperature 80℃, reaction pressure 0.6MPa, and the molar ratio of methanol to the feedstock adipic acid is 1.0:1.

[0054] The operating conditions of the catalytic distillation deep reactor are: column top temperature 70℃, reaction pressure 0.1MPa, the molar ratio of methanol to the feedstock adipic acid is 0.5:1, and the reflux ratio is 1:1.

[0055] The molar ratio of cyclohexane feed amount to adipic acid is 20:1.

[0056] The water oil mass ratio of the water washing column is 5:1.

[0057] The operating conditions of the methanol recovery column are: column top temperature 60℃, reaction pressure normal pressure, and the reflux ratio is 5:1.

[0058] The reaction sections of the monomethyl ester reactor, the dimethyl ester reactor and the catalytic distillation deep reactor are filled with macroporous strong acid cation resin catalysts.

[0059] The catalytic distillation deep reactor comprises a rectification section, a reaction section and a stripping section. The rectification section has 20 theoretical plates, the catalyst in the reaction section is divided into 10 sections, each section has a plate in the middle and has 2 theoretical plates. The stripping section has 10 theoretical plates.

[0060] The adipic acid treated by the above device and method is reacted with methanol to produce dimethyl adipate, the conversion rate of adipic acid is 99.63%, the purity of dimethyl adipate is 99.87%, and the yield of dimethyl adipate is 99.37%.

[0061] Example 3

[0062] The device described in Example 1 is used, wherein the operating conditions of the monomethyl ester reactor are: reaction temperature 90℃, reaction pressure 0.8MPa, and the molar ratio of methanol to feedstock adipic acid is 1.2:1.

[0063] The operating conditions of the dimethyl ester reactor are: reaction temperature 100℃, reaction pressure 0.8MPa, and the molar ratio of methanol to feedstock adipic acid is 2.0:1.

[0064] The operating conditions of the catalytic distillation deep reactor are: tower top temperature 80℃, reaction pressure 0.2MPa, the molar ratio of methanol to feedstock adipic acid is 1.0:1, and the reflux ratio is 2:1.

[0065] The molar ratio of cyclohexane feedstock to adipic acid is 30:1.

[0066] The water-oil mass ratio of the water washing tower is 10:1.

[0067] The operating conditions of the methanol recovery tower are: tower top temperature 80℃, reaction pressure 0.3MPa, and the reflux ratio is 10:1.

[0068] The reaction sections of the monomethyl ester reactor, the dimethyl ester reactor and the catalytic distillation deep reactor are filled with macroporous strong acid cation resin catalyst.

[0069] The catalytic distillation deep reactor includes a rectification section, a reaction section and a stripping section. The rectification section has 30 theoretical plates, the reaction section catalyst is divided into 18 sections, each section has a plate in the middle, and the theoretical plate number is 2. The stripping section has 20 theoretical plates.

[0070] The adipic acid treated by the above device and method is reacted with methanol to produce dimethyl adipate, the conversion rate of adipic acid is 99.63%, the purity of dimethyl adipate is 99.87%, and the yield of dimethyl adipate is 99.37%.

[0071] Example 4

[0072] The device described in Example 1 is used, wherein the operating conditions of the monomethyl ester reactor are: reaction temperature 80℃, reaction pressure 0.7MPa, and the molar ratio of methanol to feedstock adipic acid is 1.15:1.

[0073] The operating conditions of the dimethyl ester reactor are: reaction temperature 90℃, reaction pressure 0.7MPa, and the molar ratio of methanol to feedstock adipic acid is 1.5:1.

[0074] The operating conditions of the catalytic distillation deep reactor were as follows: tower top temperature 75°C, reaction pressure 0.15 MPa, molar ratio of methanol to feedstock adipic acid 0.8:1, reflux ratio 1.5:1.

[0075] The molar ratio of cyclohexane feedstock to adipic acid was 25:1.

[0076] The water-oil mass ratio of the water washing tower was 8:1.

[0077] The operating conditions of the methanol recovery tower were as follows: tower top temperature 70°C, reaction pressure 0.2 MPa, reflux ratio 8:1.

[0078] The single methyl ester reactor, the double methyl ester reactor and the reaction section of the catalytic distillation deep reactor were filled with macroporous strong acid cation resin catalyst.

[0079] The catalytic distillation deep reactor included a rectification section, a reaction section and a stripping section. The rectification section had 25 theoretical plates, the reaction section catalyst was divided into 14 sections, each section had a plate in the middle and the theoretical plate number was 2. The stripping section had 15 theoretical plates.

[0080] The adipic acid treated by the above device and method was reacted with methanol to produce adipic acid dimethyl ester, the conversion rate of adipic acid was 99.42%, the purity of adipic acid dimethyl ester was 99.61%, and the yield of adipic acid dimethyl ester was 99.28%.

[0081] Example 5

[0082] The device described in Example 1 was used, wherein the operating conditions of the single methyl ester reactor were as follows: reaction temperature 75°C, reaction pressure 0.65 MPa, molar ratio of methanol to feedstock adipic acid 1.12:1.

[0083] The operating conditions of the double methyl ester reactor were as follows: reaction temperature 95°C, reaction pressure 0.65 MPa, molar ratio of methanol to feedstock adipic acid 1.2:1.

[0084] The operating conditions of the catalytic distillation deep reactor were as follows: tower top temperature 72°C, reaction pressure 0.12 MPa, molar ratio of methanol to feedstock adipic acid 0.6:1, reflux ratio 1.4:1.

[0085] The molar ratio of cyclohexane feedstock to adipic acid was 23:1.

[0086] The water-oil mass ratio of the water washing tower was 6:1.

[0087] The operating conditions of the methanol recovery tower were as follows: tower top temperature 65°C, reaction pressure 0.1 MPa, reflux ratio 6:1.

[0088] The reaction section of the monomethyl ester reactor, the dimethyl ester reactor and the catalytic distillation deep reactor is packed with macroporous strong acid cation resin catalyst.

[0089] The catalytic distillation deep reactor comprises a rectification section, a reaction section and a stripping section. The rectification section has 22 theoretical plates, the catalyst in the reaction section is divided into 13 sections, each section has a plate in the middle and has 2 theoretical plates. The stripping section has 14 theoretical plates.

[0090] The adipic acid treated by the above device and method is reacted with methanol to produce dimethyl adipate, the conversion rate of adipic acid is 99.38%, the purity of dimethyl adipate is 99.73%, and the yield of dimethyl adipate is 99.54%.

[0091] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0092] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A production apparatus for dimethyl adipate, characterized in that, This includes monomethyl ester reactors, dimethyl ester reactors, catalytic distillation deep reactors, methanol extraction towers, and methanol recovery towers; The monomethyl ester reactor, dimethyl ester reactor, catalytic distillation deep reactor, methanol extraction tower and methanol recovery tower are connected in sequence. The bottom inlet of the monomethyl ester reactor is connected to the first mixer via the monomethyl ester reactor feed pipe, and the inlet of the first mixer is connected to the adipic acid feed pipe and the methanol feed pipe, respectively. The top outlet of the monomethyl ester reactor is connected to the bottom inlet of the dimethyl ester reactor via the monomethyl ester reactor outlet pipe. A second mixer is provided between the monomethyl ester reactor outlet pipe and the dimethyl ester reactor inlet pipe. The inlet of the second mixer is also connected to a first supplementary methanol tank. The top outlet of the dimethyl ester reactor is connected to the upper inlet of the catalytic distillation deep reactor via the dimethyl ester reactor outlet pipe, and the lower inlet of the catalytic distillation deep reactor is connected to a second replenishing methanol tank; the lower outlet of the catalytic distillation deep reactor discharges the produced dimethyl adipic acid through a pipeline. The upper outlet of the catalytic distillation deep reactor is connected to the lower inlet of the methanol extraction tower through the catalytic distillation tower outlet pipe. The bottom outlet of the methanol extraction tower is connected to the inlet of the methanol recovery tower via a methanol water pipe.

2. The apparatus for producing dimethyl adipate according to claim 1, characterized in that, The upper outlet of the methanol extraction tower is connected to the third mixer via a circulating cyclohexane pipe, and the outlet of the third mixer is connected to the lower inlet of the catalytic distillation deep reactor via a cyclohexane feed pipe of the catalytic distillation tower; the inlet of the third mixer is also connected to a supplementary cyclohexane tank.

3. The apparatus for producing dimethyl adipate according to claim 1, characterized in that, The bottom outlet of the methanol recovery tower is connected to the upper inlet of the methanol extraction tower via an extraction water pipe.

4. The apparatus for producing dimethyl adipate according to claim 1 or 3, characterized in that, The recovered methanol is discharged from the upper outlet of the methanol recovery tower.

5. A method for producing dimethyl adipate, characterized in that, Using the apparatus according to any one of claims 1-4, the steps include: (1) Adipic acid and methanol are first mixed and then fed into a monomethyl ester reactor, where adipic acid is converted into monomethyl adipic acid. (2) The material from the monomethyl ester reactor outlet and the supplemented methanol are mixed and then enter the dimethyl ester reactor. In the dimethyl ester reactor, monomethyl adipic acid is converted into dimethyl adipic acid. (3) The product enters the upper part of the reaction section of the catalytic distillation deep reactor through the outlet of the dimethyl ester reactor. Methanol and cyclohexane are added from the lower part of the reaction section of the catalytic distillation deep reactor. The separation of methanol and ester is completed in the stripping section of the catalytic distillation deep reactor. The methanol, cyclohexane and generated water at the top of the column enter the methanol water washing column. The cyclohexane at the top of the column is recycled. The water containing methanol in the bottom of the column enters the methanol recovery column to recover methanol and is recycled. In the reaction section, the monoester and the rising methanol come into contact and react under the action of the catalyst. The unreacted monoester is converted into diester and flows out from the bottom of the column. The generated water is carried out of the reaction system by the azeotropic cyclohexane.

6. The method for producing dimethyl adipate according to claim 5, characterized in that, The reaction temperature of the monomethyl ester reactor is 70–90°C, the reaction pressure is 0.6–0.8 MPa, and the molar ratio of methanol to adipic acid is 1.1–1.2:

1.

7. The method for producing dimethyl adipate according to claim 6, characterized in that, The reaction temperature of the dimethyl ester reactor is 80–100°C, the reaction pressure is 0.6–0.8 MPa, and the molar ratio of supplemented methanol to the original feed adipic acid is 1.0–2.0:

1.

8. The method for producing dimethyl adipate according to claim 7, characterized in that, The top temperature of the catalytic distillation deep reactor is 70-80℃, the reaction pressure is 0.1-0.2MPa, the molar ratio of supplementary methanol to original feed adipic acid is 0.5-1.0:1, and the reflux ratio is 1-2:

1. The molar ratio of the supplementary cyclohexane to the original feed adipic acid is 20-30:

1.

9. A method for producing dimethyl adipate according to claim 5 or 8, characterized in that, The water-to-oil mass ratio in the methanol washing tower is 5-10:

1. The methanol recovery tower has a top temperature of 60-80℃, a reaction pressure of atmospheric pressure to 0.3MPa, and a reflux ratio of 5-10:

1.

10. The method for producing dimethyl adipate according to claim 5, characterized in that, The reaction sections of the monomethyl ester reactor, dimethyl ester reactor, and catalytic distillation depth reactor are all packed with macroporous strong acidic cationic resin catalysts. The catalytic distillation deep reactor comprises, from top to bottom, a rectification section, a reaction section, and a stripping section. The rectification section has 20 to 30 theoretical plates; the catalyst in the reaction section is divided into 10 to 18 sections, each with a tray in the middle, and has 2 theoretical plates; the stripping section has 10 to 20 theoretical plates.

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