Separation method of dimethyl carbonate and methanol

Abstract

The invention belongs to the field of dimethyl carbonate preparation, and discloses a dimethyl carbonate and methanol separation method, which comprises the following operation steps: S10, respectively feeding an azeotropic mixture of dimethyl carbonate and methanol and a mixed solution of dimethyl sulfoxide and epoxypropane into an azeotrope feed port and a mixed solution feed port of an extraction reaction rectifying tower; s20, extracting a mixed material liquid from the tower kettle of the extraction reaction rectifying tower, and extracting methanol from the tower top of the extraction reaction rectifying tower; s30, feeding the mixed material liquid into a first rectifying tower for vacuum rectification, extracting a dimethyl carbonate product from the tower top, and extracting mixed liquid from the tower kettle; s40, feeding the mixed solution into a second rectifying tower for vacuum rectification; according to the method, the high-efficiency online continuous separation effect is achieved, complicated process conditions do not need to be set, the selected entrainer is wide in raw material source, the energy consumption is low, the operation cost is reasonable, and the method is suitable for being used as a separation process for industrial implementation and application.

Description

Technical Field

[0001] The invention belongs to the field of preparation of dimethyl carbonate, and particularly relates to a method for separating dimethyl carbonate and methanol. Background Art

[0002] Dimethyl carbonate (DMC) is a low-toxic, environmentally friendly, and widely used chemical raw material. Due to its good reactivity, it can replace highly toxic substances such as phosgene and methyl chloroformate to carry out carbonylation, carbonyl methoxylation, and methylation reactions. It is also widely used as an organic synthesis intermediate in pesticides, medicines, polymer synthesis, and battery electrolytes.

[0003] The existing preparation and synthesis of dimethyl carbonate mainly includes two industrial synthesis methods: one is the ester exchange synthesis route, which is prepared by ester exchange reaction of ethylene carbonate or propylene carbonate and methanol, and propylene glycol and ethylene glycol are co-produced; the other is the carbonylation oxidation synthesis route, which is prepared by carbonylation oxidation reaction of methanol with oxygen and carbon monoxide; in these two industrial synthesis methods, methanol cannot be completely converted, and the final crude product will form an azeotropic mixture of dimethyl carbonate and methanol, which must be separated to obtain pure DMC.

[0004] The separation technologies that are currently widely used mainly include extractive distillation, pressure swing distillation and azeotropic distillation. These separation technologies all have advantages and disadvantages. Among them, the separation process energy consumption and operating cost of extractive distillation are low, and the separation process is relatively efficient, but it is difficult to find an ideal extractant (either it is prone to entrainment problems, or the source of the extractant is single or the operating conditions of the extractant are costly or the separation efficiency is low; or it causes methanol or dimethyl carbonate to form new azeotropic components); pressure swing distillation is an environmentally friendly separation process that does not require the introduction of any third component, but because it needs to set process conditions for pressure changes, its energy consumption and operating costs are relatively high; although the energy consumption and operating costs of azeotropic distillation are suitable for implementation, it is difficult to obtain high-purity dimethyl carbonate.

[0005] Therefore, the applicant hopes to seek technical solutions to solve the above technical problems. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for separating dimethyl carbonate and methanol, which achieves a high-efficiency online continuous separation effect, does not need to set complicated process conditions, uses a wide range of entrainer raw materials, and has low energy consumption and reasonable operating costs for the separation process, and is very suitable as a separation process for industrial implementation and application.

[0007] The technical solution adopted by the present invention is as follows: A method for separating dimethyl carbonate and methanol comprises the following steps: S10, feeding the azeotropic mixture of dimethyl carbonate and methanol and the mixed liquid of dimethyl sulfoxide and propylene oxide into the azeotrope feed port and the mixed liquid feed port of the extractive reaction distillation tower respectively; S20, in an extractive reaction distillation tower filled with a catalyst, part of the methanol in the azeotropic mixture is mixed with Propylene oxide in the mixed liquid reacts to generate propylene glycol methyl ether; a mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is extracted from the bottom of the extractive reaction distillation tower, and methanol is extracted from the top of the extractive reaction distillation tower; S30, sending the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether into a first distillation tower for vacuum distillation, extracting the dimethyl carbonate product from the top of the first distillation tower, and extracting the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether from the bottom of the first distillation tower; S40, sending the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether into a second distillation tower for vacuum distillation, extracting propylene glycol methyl ether from the top of the second distillation tower, and extracting dimethyl sulfoxide from the bottom of the second distillation tower.

[0008] Preferably, the number of theoretical plates of the extractive reaction distillation tower is 35-50; the feeding position of the azeotrope feed port is the 15th-25th plate; and the feeding position of the mixed liquid feed port is the 3rd-6th plate.

[0009] Preferably, in step S10, the mass fraction of dimethyl carbonate in the azeotropic mixture of dimethyl carbonate and methanol is 25-45%; the mass fraction of dimethyl sulfoxide in the mixed solution of dimethyl sulfoxide and propylene oxide is 45-65%; and the molar ratio of propylene oxide in the mixed solution of dimethyl sulfoxide and propylene oxide to methanol in the azeotropic mixture of dimethyl carbonate and methanol is 1:4-8.

[0010] Preferably, in step S10, the mixed liquid of dimethyl sulfoxide and propylene oxide is prepared by continuously feeding and mixing dimethyl sulfoxide and propylene oxide in a tube-in-tube mixer, and the output end of the tube-in-tube mixer is connected to the mixed liquid feed port through a pipeline.

[0011] Preferably, in step S20, the tower pressure of the extraction reaction distillation tower is 0.12-0.2 MPa; the bottom temperature of the extraction reaction distillation tower is set to 90-105°C, and the top temperature of the extraction reaction distillation tower is set to 60-80°C; the reflux ratio of the extraction reaction distillation tower is set to 1-5; and the catalyst uses a quaternary ammonium salt catalyst.

[0012] Preferably, in step S30, the tower pressure of the first distillation tower is 0.05-0.08 MPa; the bottom temperature of the first distillation tower is set to 105-120°C, the top temperature of the first distillation tower is set to 80-100°C; and the reflux ratio of the first distillation tower is set to 3-6.

[0013] Preferably, in step S40, the tower pressure of the second distillation tower is 0.05-0.07 MPa; the bottom temperature of the second distillation tower is set to 135-150° C., the top temperature of the second distillation tower is set to 110-130° C.; and the reflux ratio of the second distillation tower is set to 3-6.

[0014] Preferably, the extractive reaction distillation tower is provided with a first condenser at the top and a first reboiler at the bottom; the first distillation tower is provided with a second condenser at the top and a second reboiler at the bottom; the second distillation tower is provided with a third condenser at the top and a third reboiler at the bottom.

[0015] Preferably, the purity of methanol extracted from the top of the extractive reaction distillation tower is not less than 99%, and it is connected to a methanol storage tank; the purity of the dimethyl carbonate product extracted from the top of the first distillation tower is not less than 99%, and it is connected to a dimethyl carbonate product storage tank.

[0016] Preferably, the dimethyl sulfoxide withdrawn from the bottom of the second distillation tower is connected to a mixing device of dimethyl sulfoxide and propylene oxide for recycling.

[0017] It should be particularly noted that the azeotropic mixture of dimethyl carbonate and methanol referred to in the entire application generally refers to the crude dimethyl carbonate output from the dimethyl carbonate synthesis production line; the propylene glycol methyl ether referred to in the entire application includes a series of homologues such as dipropylene glycol methyl ether and tripropylene glycol methyl ether (produced by further reaction of propylene glycol methyl ether and propylene oxide), and these components are collectively referred to as "propylene glycol methyl ether" in the present application.

[0018] The present invention proposes to extract and distill dimethyl carbonate in an azeotropic mixture and to react and distill methanol in the azeotropic mixture in an extractive reaction distillation tower at the same time, and the two separation methods are carried out in coordination, wherein dimethyl sulfoxide extracts and separates dimethyl carbonate, and propylene oxide reacts with methanol to generate propylene glycol methyl ether (an environmentally friendly organic solvent with a wide range of applications), and the generated propylene glycol methyl ether can further promote the extraction and separation process, so that the extraction and separation and reaction separation processes are significantly more efficient, and there is no need to use too much extractant, and there is no need to set complex reaction conditions, and high-purity methanol can be directly separated at the top of the extractive reaction distillation tower; in addition, since the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is subjected to subsequent vacuum distillation, a high-purity dimethyl carbonate product can be obtained efficiently and quickly; the separation method of dimethyl carbonate and methanol provided by the present application realizes a high-efficiency online continuous separation effect, does not need to set complicated process conditions, the selected entrainer raw material has a wide source, and the separation process has low energy consumption and reasonable operating cost, and is very suitable as a separation process for industrial implementation and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flowchart of the operation steps of the method for separating dimethyl carbonate and methanol in a specific embodiment of the present invention; Figure 2 Schematic diagram of the device connection structure used in the method for separating dimethyl carbonate and methanol in Example 1 of the present invention; Figure 3 This is a sample photo of the dimethyl carbonate product produced in Example 1 of the present invention; Figure 4 This is a chromatogram of the dimethyl carbonate product extracted in Example 1 of the present invention (detected by gas chromatography SDMC, with an injection volume of 0.5 µL). DETAILED DESCRIPTION

[0020] See also Figure 1 As shown, this embodiment provides a method for separating dimethyl carbonate and methanol, comprising the following steps: S10, feeding the azeotropic mixture of dimethyl carbonate and methanol and the mixed solution of dimethyl sulfoxide and propylene oxide into the azeotrope feed port and the mixed solution feed port of the extractive reaction distillation tower respectively; preferably, in this step S10, the mass fraction of dimethyl carbonate in the azeotropic mixture of dimethyl carbonate and methanol is 25-45% (more preferably 28-35%); the mass fraction of dimethyl sulfoxide in the mixed solution of dimethyl sulfoxide and propylene oxide is 45-65% (more preferably 50-60%); the molar ratio of propylene oxide in the mixed solution of dimethyl sulfoxide and propylene oxide to methanol in the azeotropic mixture of dimethyl carbonate and methanol is 1:4-8 (more preferably 1:5-7); the mixed solution of dimethyl sulfoxide and propylene oxide is continuously fed and mixed with dimethyl sulfoxide and propylene oxide in a tube-in-tube mixer, and the output end of the tube-in-tube mixer is connected to the mixed solution feed port through a pipeline; S20, in an extractive reaction distillation tower filled with a catalyst, part of the methanol in the azeotropic mixture is mixed with Propylene oxide in the mixed liquid reacts to generate propylene glycol methyl ether; a mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is extracted from the bottom of the extractive reaction distillation tower, and methanol is extracted from the top of the extractive reaction distillation tower; preferably, in this step S20, the purity of the methanol extracted from the top of the extractive reaction distillation tower is not less than 99% (the purity is usually higher than 99.7%), and it is connected to a methanol storage tank; S30, sending the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether into a first distillation tower for vacuum distillation, extracting the dimethyl carbonate product from the top of the first distillation tower, and extracting the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether from the bottom of the first distillation tower; preferably, in this step S30, the purity of the dimethyl carbonate product extracted from the top of the first distillation tower is not less than 99%, preferably greater than 99.9%, more preferably greater than 99.99%, and it is connected to the dimethyl carbonate product storage tank; S40, sending the mixed solution of dimethyl sulfoxide and propylene glycol methyl ether into the second distillation tower for vacuum distillation, extracting propylene glycol methyl ether from the top of the second distillation tower, and extracting dimethyl sulfoxide from the bottom of the second distillation tower; preferably, in this step S40, the purity of propylene glycol methyl ether extracted from the top of the second distillation tower is not less than 99%, and it is connected to the propylene glycol methyl ether storage tank; the purity of dimethyl sulfoxide extracted from the bottom of the second distillation tower is not less than 95%, more preferably not less than 97%; the dimethyl sulfoxide extracted from the bottom of the second distillation tower is connected to a tube-and-tube mixer for recycling; Preferably, in this embodiment, in order to facilitate the separation effect of the separation process provided by this embodiment, in this embodiment, the structure of the relevant device and the process parameter scheme are recommended to be set as follows: The number of theoretical plates of the extractive reaction distillation tower is 35-50; the feeding position of the azeotrope feed port is the 15th-25th plate; the feeding position of the mixed liquid feed port is the 3rd-6th plate; the top of the extractive reaction distillation tower is provided with a first condenser, and the bottom of the tower is provided with a first reboiler; the tower pressure of the extractive reaction distillation tower is 0.12-0.2MPa; the tower kettle temperature of the extractive reaction distillation tower is set to 90-105°C, and the tower top temperature of the extractive reaction distillation tower is set to 60-80°C; the reflux ratio of the extractive reaction distillation tower is set to 1-5; The extractive reaction distillation tower comprises a distillation section located at the top, a reaction section located in the middle and a stripping section located at the bottom; the reaction section is filled with a quaternary ammonium salt catalyst; Preferably, the number of theoretical plates of the first distillation tower is 25-40; the feeding position of the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is the 12th-18th plate; the top of the first distillation tower is provided with a second condenser, and the bottom of the first distillation tower is provided with a second reboiler; the tower pressure of the first distillation tower is 0.05-0.08MPa; the bottom temperature of the first distillation tower is set to 105-120°C, and the top temperature of the first distillation tower is set to 80-100°C; the reflux ratio of the first distillation tower is set to 3-6; Preferably, the number of theoretical plates of the second distillation tower is 20-30; the feeding position of the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is the 10th-12th block; a third condenser is provided at the top of the second distillation tower, and a third reboiler is provided at the bottom of the tower; the tower pressure of the second distillation tower is 0.05-0.07MPa; the bottom temperature of the second distillation tower is set to 135-150°C, and the top temperature of the second distillation tower is set to 110-130°C; the reflux ratio of the second distillation tower is set to 3-6.

[0021] It should be noted that the present application has cited various preferred range parameters for the above embodiments through a large number of trial and error experiments. Those skilled in the art can choose within these preferred parameter ranges (including endpoint values ​​and intermediate values) according to actual conditions. In order to save space in the specification, the present embodiments will not be expanded one by one.

[0022] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention. Embodiment 1:

[0023] Please refer to Figure 2 As shown, firstly, the following device is selected to implement the separation process of this embodiment 1: The number of theoretical plates of the extractive reaction distillation tower 100 is 40; the feeding position of the azeotrope feed port is the 18th plate; the feeding position of the mixed liquid feed port is the 4th plate; the top of the extractive reaction distillation tower 100 is provided with a first condenser 110, and the bottom of the tower is provided with a first reboiler 120; the tower pressure of the extractive reaction distillation tower 100 is normal pressure; the bottom temperature of the extractive reaction distillation tower 100 is set to 95°C, and the top temperature of the extractive reaction distillation tower 100 is set to 70°C; the reflux ratio of the extractive reaction distillation tower 100 is set to 1.5; the extractive reaction distillation tower 100 includes a distillation section located at the top (tower top to the 17th plate), a reaction section located in the middle (the 18th plate to the 30th plate) and a stripping section located at the bottom (the 31st plate to the bottom); a quaternary ammonium salt catalyst is filled in the reaction section; The number of theoretical plates of the first distillation tower 200 is 35; the feeding position of the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is the 15th plate; a second condenser 210 is provided at the top of the first distillation tower 200, and a second reboiler 220 is provided at the bottom; the tower pressure of the first distillation tower 200 is 0.06 MPa; the bottom temperature of the first distillation tower 200 is set to 110° C., and the top temperature of the first distillation tower 200 is set to 90° C.; the reflux ratio of the first distillation tower 200 is set to 4; The number of theoretical plates of the second distillation tower 300 is 25; the feeding position of the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is the 12th plate; the top of the second distillation tower 300 is provided with a third condenser 310, and the bottom of the second distillation tower 300 is provided with a third reboiler 320; the tower pressure of the second distillation tower 300 is 0.06MPa; the bottom temperature of the second distillation tower 300 is set to 140°C, and the top temperature of the second distillation tower 300 is set to 120°C; the reflux ratio of the second distillation tower 300 is set to 3; The purity of each material was tested using an Agilent 7890A chromatograph.

[0024] This embodiment 1 is operated according to the following steps: (1) Dimethyl sulfoxide (from the dimethyl sulfoxide raw material tank 430) and propylene oxide (from the propylene oxide raw material tank 440) are fed into the tube mixer 500 at a mass ratio of 1:1 for static mixing to obtain a mixed solution of dimethyl sulfoxide and propylene oxide; (2) The crude dimethyl carbonate (i.e., an azeotropic mixture of dimethyl carbonate and methanol, with a dimethyl carbonate content of about 30%) output from the dimethyl carbonate synthesis production line is fed into the mixed liquid feed port and the azeotrope feed port of the extractive reaction distillation column 100, respectively; the molar ratio of propylene oxide in the mixed liquid to methanol in the azeotropic mixture is 1:6; (3) In the extractive reaction distillation tower 100, all the propylene oxide reacts with part of the methanol to generate propylene glycol methyl ether. Both propylene glycol methyl ether and dimethyl sulfoxide are used as extractants to quickly separate dimethyl carbonate from the azeotropic mixture. A mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is extracted from the bottom of the extractive reaction distillation tower 100, and methanol is extracted from the top of the extractive reaction distillation tower 100. After content detection, the purity of methanol is 99.91%, and it is connected to the methanol storage tank 410; (4) The mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is sent to the first distillation tower 200 for vacuum distillation, and the dimethyl carbonate product is extracted from the top of the first distillation tower 200, and the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is extracted from the bottom of the first distillation tower 200; after content detection, the purity of the dimethyl carbonate product is greater than 99.99%, and the yield is about 93%. The product is connected to the dimethyl carbonate product storage tank 400, and the dimethyl carbonate product is stored in the storage tank 400. Figure 3 Sample photos shown, and Figure 4 Product chromatogram shown; (5) The mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is sent to the second distillation tower 300 for vacuum distillation, and propylene glycol methyl ether is extracted from the top of the second distillation tower 300 and connected to the propylene glycol methyl ether storage tank 420; dimethyl sulfoxide is extracted from the bottom of the second distillation tower 300; after content detection, the purity of propylene glycol methyl ether is 99.98%, and the purity of dimethyl sulfoxide is 99.3%; (6) The dimethyl sulfoxide obtained in the above step (5) is connected to the dimethyl sulfoxide feed pipeline of the tube-in-tube mixer 500.

[0025] Embodiment 2: The remaining technical scheme of this embodiment 2 is the same as that of embodiment 1, except that, in this embodiment 2, the number of theoretical plates of the extractive reaction distillation tower 100 is 35; the feeding position of the azeotrope feed port is the 18th plate; the feeding position of the mixed liquid feed port is the 3rd plate; the tower pressure of the extractive reaction distillation tower 100 is 0.13MPa; the bottom temperature of the extractive reaction distillation tower 100 is set to 100°C, and the top temperature of the extractive reaction distillation tower 100 is set to 75°C; the reflux ratio of the extractive reaction distillation tower 100 is set to 2.

[0026] Embodiment 3: The rest of the technical scheme of this embodiment 3 is the same as that of embodiment 1, with the only difference being that, in this embodiment 3, the number of theoretical plates of the first distillation tower 200 is 25; the feeding position of the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is the 13th plate; the tower pressure of the first distillation tower 200 is 0.08 MPa; the bottom temperature of the first distillation tower 200 is set to 115°C, and the top temperature of the first distillation tower 200 is set to 95°C; the reflux ratio of the first distillation tower 200 is set to 5.

[0027] Embodiment 4: The rest of the technical scheme of this embodiment 4 is the same as that of embodiment 1, with the only difference being that, in this embodiment 4, the number of theoretical plates of the second distillation tower 300 is 25; the feeding position of the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is the 13th plate; the tower pressure of the second distillation tower 300 is 0.07 MPa; the bottom temperature of the second distillation tower 300 is set to 145°C, and the top temperature of the second distillation tower 300 is set to 125°C; the reflux ratio of the second distillation tower 300 is set to 4.

[0028] Example 5: The rest of the technical scheme of Example 5 is the same as that of Example 1, with the only difference being that, in Example 5, dimethyl sulfoxide and propylene oxide are fed into the tube-in-tube mixer 500 at a mass ratio of 1.3:1 for static mixing.

[0029] Example 6: The rest of the technical scheme of Example 6 is the same as that of Example 1, except that, in Example 6, the molar ratio between propylene oxide in the mixed liquid and methanol in the azeotropic mixture is 1:5.

[0030] Example 7: The rest of the technical scheme of Example 7 is the same as that of Example 1, except that, in Example 7, the molar ratio between propylene oxide in the mixed liquid and methanol in the azeotropic mixture is 1:7.

[0031] Comparative Example 1: The rest of the technical solutions of this comparative example 1 are the same as those of Example 1, with the only difference being that, in this comparative example 1, the tube-in-tube mixer 500 is eliminated, and the dimethyl sulfoxide feed pipeline is directly connected to the mixed liquid feed port of the extraction reaction distillation tower 100, without being connected to the propylene oxide feed pipeline.

[0032] Comparative Example 2: The rest of the technical solutions of this comparative example 2 are the same as those of Example 1, with the only difference being that, in this comparative example 2, the tube-in-tube mixer 500 is eliminated, and the propylene oxide feed line is directly connected to the mixed liquid feed port of the extraction reaction distillation tower 100, without being connected to the dimethyl sulfoxide feed line.

[0033] Comparative Example 3: The rest of the technical solutions of this comparative example 3 are the same as those of Example 1, with the only difference being that, in this comparative example 3, the tube-in-tube mixer 500 is eliminated, and the propylene oxide feed pipeline and the dimethyl sulfoxide feed pipeline are directly connected to the mixed liquid feed port of the extraction reaction distillation tower 100, respectively.

[0034] Comparative Example 4: The rest of the technical solutions of this comparative example 4 are the same as those of Example 1, with the only difference being that, in this comparative example 4, propylene carbonate is used to replace the dimethyl sulfoxide in Example 1, which may react with propylene oxide to produce impurities.

[0035] Comparative Example 5: The remaining technical solutions of Comparative Example 5 are the same as those of Example 1, except that, in Comparative Example 5, water is used to replace the dimethyl sulfoxide in Example 1.

[0036] Comparative Example 6: The remaining technical solutions of this comparative example 6 are the same as those of Example 1, except that in this comparative example 6, benzene is used to replace the dimethyl sulfoxide in Example 1, but it has poor miscibility with propylene oxide and will produce a new azeotropic problem with methanol.

[0037] The applicant also tested the contents of the relevant components obtained in Examples 2-7 and Comparative Examples 1-6, and the test results are shown in Table 1 below:

[0038] Note: The “ / ” in Table 1 above means that it has been confirmed that the test data of the relevant components of this comparative example do not meet the requirements, so no subsequent testing was performed on other components obtained from this comparative example.

[0039] The implementation results of the above-mentioned embodiments and comparative examples in the present application can confirm that the separation process of dimethyl carbonate and methanol provided in the embodiments of the present application achieves a high-efficiency online continuous separation effect without setting complicated process conditions. The selected entrainer raw materials have a wide range of sources, low energy consumption and reasonable operating costs. Therefore, it is very suitable as a separation process for industrial implementation and application.

[0040] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0041] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for separating dimethyl carbonate and methanol, characterized in that: The steps are as follows: S10, feeding the azeotropic mixture of dimethyl carbonate and methanol and the mixed liquid of dimethyl sulfoxide and propylene oxide into the azeotrope feed port and the mixed liquid feed port of the extractive reaction distillation tower respectively; S20, in an extractive reaction distillation tower filled with a catalyst, part of the methanol in the azeotropic mixture is mixed with Propylene oxide in the mixed liquid reacts to generate propylene glycol methyl ether; a mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is extracted from the bottom of the extractive reaction distillation tower, and methanol is extracted from the top of the extractive reaction distillation tower; S30, sending the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether into a first distillation tower for vacuum distillation, extracting the dimethyl carbonate product from the top of the first distillation tower, and extracting the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether from the bottom of the first distillation tower; S40, sending the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether into a second distillation tower for vacuum distillation, extracting propylene glycol methyl ether from the top of the second distillation tower, and extracting dimethyl sulfoxide from the bottom of the second distillation tower.

2. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: The number of theoretical plates of the extractive reaction distillation tower is 35-50; the feeding position of the azeotrope feeding port is the 15th-25th plate; and the feeding position of the mixed liquid feeding port is the 3rd-6th plate.

3. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: In the step S10, the mass fraction of dimethyl carbonate in the azeotropic mixture of dimethyl carbonate and methanol is 25-45%; the mass fraction of dimethyl sulfoxide in the mixed solution of dimethyl sulfoxide and propylene oxide is 45-65%; and the molar ratio of propylene oxide in the mixed solution of dimethyl sulfoxide and propylene oxide to methanol in the azeotropic mixture of dimethyl carbonate and methanol is 1:4-8.

4. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: In the step S10, the mixed liquid of dimethyl sulfoxide and propylene oxide is prepared by continuously feeding and mixing dimethyl sulfoxide and propylene oxide in a tube-in-tube mixer, and the output end of the tube-in-tube mixer is connected to the mixed liquid feed port through a pipeline.

5. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: In step S20, the tower pressure of the extraction reaction distillation tower is 0.12-0.2 MPa; the bottom temperature of the extraction reaction distillation tower is set to 90-105° C., and the top temperature of the extraction reaction distillation tower is set to 60-80° C.; the reflux ratio of the extraction reaction distillation tower is set to 1-5; and the catalyst uses a quaternary ammonium salt catalyst.

6. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: In the step S30, the tower pressure of the first distillation tower is 0.05-0.08 MPa; the bottom temperature of the first distillation tower is set to 105-120° C., the top temperature of the first distillation tower is set to 80-100° C.; and the reflux ratio of the first distillation tower is set to 3-6.

7. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: In the step S40, the tower pressure of the second distillation tower is 0.05-0.07 MPa; the bottom temperature of the second distillation tower is set to 135-150° C., the top temperature of the second distillation tower is set to 110-130° C.; and the reflux ratio of the second distillation tower is set to 3-6.

8. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: The extractive reaction distillation tower is provided with a first condenser at the top and a first reboiler at the bottom; the first distillation tower is provided with a second condenser at the top and a second reboiler at the bottom; the second distillation tower is provided with a third condenser at the top and a third reboiler at the bottom.

9. The method for separating dimethyl carbonate and methanol according to claim 1, characterized in that: The purity of methanol extracted from the top of the extraction reaction distillation tower is not less than 99%, and it is connected to the methanol storage tank; the purity of the dimethyl carbonate product extracted from the top of the first distillation tower is not less than 99%, and it is connected to the dimethyl carbonate product storage tank.

10. The method for separating dimethyl carbonate and methanol according to claim 1 or 9, characterized in that: The dimethyl sulfoxide withdrawn from the bottom of the second distillation tower is connected to a mixing device of dimethyl sulfoxide and propylene oxide for recycling.

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