A method for separating dimethyl carbonate and methanol
By using a mixture of dimethyl sulfoxide and propylene oxide and azeotropic mixture in the extraction reaction distillation tower for synergistic extraction and reaction separation, the problem of methanol in the prior art cannot be completely converted and separated efficiency is solved, and the separation effect of dimethyl carbonate and methanol with high efficiency and low energy consumption is achieved.
Patent Information
- Application Number
- CN202510186479.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-06-03
- Estimated Expiration
- 2045-02-20
AI Technical Summary
In the existing preparation process of dimethyl carbonate, methanol cannot be completely converted, resulting in the crude product being an azeotropic mixture of dimethyl carbonate and methanol, making it difficult to achieve efficient separation. The existing separation technology has problems such as high energy consumption, high operating costs, and difficulty in obtaining high-purity products.
A separation method of dimethyl carbonate and methanol is adopted. By using a mixture of dimethyl sulfoxide and propylene oxide and an azeotropic mixture in the extraction reaction distillation tower, propylene glycol methyl ether is generated as the extraction agent, and efficient separation of dimethyl carbonate and methanol is achieved.
It achieves a high-efficiency online continuous separation effect without the need to set up complicated process conditions. The selected entrainer raw materials are widely sourced, with low energy consumption and reasonable operating costs, and are suitable for industrial application.
Smart Images
Figure CN119661360B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of the preparation of dimethyl carbonate, and particularly relates to a method for separating dimethyl carbonate and methanol. Background Art
[0002] Dimethyl carbonate (abbreviated as "DMC") is a kind of chemical raw material with low toxicity, excellent environmental protection performance and wide application. Due to its good reaction performance, it can replace highly toxic substances such as phosgene and methyl chloroformate for carbonylation, carbomethoxylation and methylation reactions, and is widely used as an organic synthesis intermediate in pesticides, pharmaceuticals, polymer synthesis and battery electrolytes.
[0003] The existing preparation and synthesis of dimethyl carbonate mainly include two industrial synthesis methods: one is the transesterification synthesis route, which is prepared by the transesterification reaction of ethylene carbonate or propylene carbonate and methanol, and co-produces propylene glycol and ethylene glycol; the other is the carbonylation oxidation synthesis route, which is prepared by the carbonylation oxidation reaction of methanol with oxygen and carbon monoxide; in these two industrial synthesis methods, methanol cannot be completely converted, and finally the crude product will form an azeotropic mixture of dimethyl carbonate and methanol, and it must be separated to obtain pure DMC.
[0004] The currently applied separation technologies mainly include extractive distillation, pressure swing distillation and azeotropic distillation. These separation technologies all have advantages and disadvantages. Among them, the separation process of extractive distillation has low energy consumption, low operating cost and relatively high efficiency, 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 cost of the extractant is high or the separation efficiency is low; either it causes the formation of new azeotropic components of methanol or dimethyl carbonate); pressure swing distillation is an environmentally friendly separation process and does not require the introduction of any third component, but due to the need to set process conditions for pressure change, its energy consumption and operating cost are relatively high; although the energy consumption and operating cost of azeotropic distillation are both suitable for implementation and application, 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 realizes high-efficiency on-line continuous separation effect, does not require the setting of complicated process conditions, the selected entrainer has a wide range of raw material sources, and the energy consumption of the separation process is low and the operating cost is reasonable, and it is very suitable as a separation process for industrial implementation and application.
[0007] The technical solution adopted by the present invention is as follows:
[0008] A method for separating dimethyl carbonate and methanol, comprising the following operating steps:
[0009] S10: Feed the azeotropic mixture of dimethyl carbonate and methanol and the mixture of dimethyl sulfoxide and propylene oxide into the azeotrope feed port and the mixture feed port of an extraction reactive distillation column respectively;
[0010] S20: In the extraction reactive distillation column filled with a catalyst, part of the methanol in the azeotropic mixture reacts with
[0011] propylene oxide in the mixture to generate propylene glycol methyl ether; withdraw the mixture of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether from the bottom of the extraction reactive distillation column, and withdraw methanol from the top of the extraction reactive distillation column;
[0012] S30: Feed the mixture of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether into a first distillation column for vacuum distillation, withdraw the dimethyl carbonate product from the top of the first distillation column, and withdraw the mixture of dimethyl sulfoxide and propylene glycol methyl ether from the bottom of the first distillation column;
[0013] S40: Feed the mixture of dimethyl sulfoxide and propylene glycol methyl ether into a second distillation column for vacuum distillation, withdraw propylene glycol methyl ether from the top of the second distillation column, and withdraw dimethyl sulfoxide from the bottom of the second distillation column.
[0014] Preferably, the number of theoretical plates of the extraction reactive distillation column is 35 - 50; the feeding position of the azeotrope feed port is the 15th - 25th plate; the feeding position of the mixture feed port is the 3rd - 6th plate.
[0015] 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 mixture of dimethyl sulfoxide and propylene oxide is 45% - 65%; the molar ratio of propylene oxide in the mixture of dimethyl sulfoxide and propylene oxide to methanol in the azeotropic mixture of dimethyl carbonate and methanol is 1:4 - 8.
[0016] Preferably, in step S10, the mixture of dimethyl sulfoxide and propylene oxide is continuously fed and mixed in a tube - shell mixer, and the output end of the tube - shell mixer is connected to the mixture feed port through a pipeline.
[0017] Preferably, in step S20, the tower pressure of the extraction reactive distillation column is 0.12 - 0.2 MPa; the bottom temperature of the extraction reactive distillation column is set at 90 - 105 °C, the top temperature of the extraction reactive distillation column is set at 60 - 80 °C; the reflux ratio of the extraction reactive distillation column is set at 1 - 5; the catalyst used is a quaternary ammonium salt catalyst.
[0018] Preferably, in step S30, the column pressure of the first distillation column is 0.05 - 0.08 MPa; the bottom temperature of the first distillation column is set to 105 - 120 °C, and the top temperature of the first distillation column is set to 80 - 100 °C; the reflux ratio of the first distillation column is set to 3 - 6.
[0019] Preferably, in step S40, the column pressure of the second distillation column is 0.05 - 0.07 MPa; the bottom temperature of the second distillation column is set to 135 - 150 °C, and the top temperature of the second distillation column is set to 110 - 130 °C; the reflux ratio of the second distillation column is set to 3 - 6.
[0020] Preferably, a first condenser is provided at the top of the extraction reactive distillation column, and a first reboiler is provided at the bottom thereof; a second condenser is provided at the top of the first distillation column, and a second reboiler is provided at the bottom thereof; a third condenser is provided at the top of the second distillation column, and a third reboiler is provided at the bottom thereof.
[0021] Preferably, the purity of the methanol drawn from the top of the extraction reactive distillation column is not less than 99%, and it is connected to a methanol storage tank; the purity of the dimethyl carbonate product drawn from the top of the first distillation column is not less than 99%, and it is connected to a dimethyl carbonate product storage tank.
[0022] Preferably, the dimethyl sulfoxide drawn from the bottom of the second distillation column is connected to a mixing device of dimethyl sulfoxide and propylene oxide for recycling.
[0023] It should be particularly noted that the azeotropic mixture of dimethyl carbonate and methanol involved throughout this application generally refers to the crude dimethyl carbonate output from the dimethyl carbonate synthesis production line; the propylene glycol methyl ether involved throughout this application includes a series of homologues such as dipropylene glycol methyl ether and tripropylene glycol methyl ether (formed by further reaction of propylene glycol methyl ether with propylene oxide), and these components are collectively referred to as "propylene glycol methyl ether" in this application.
[0024] The present invention proposes to carry out extractive distillation on dimethyl carbonate in an azeotropic mixture and reactive distillation on methanol in the azeotropic mixture simultaneously in an extraction reactive distillation column. The two separation methods cooperate with each other. Among them, dimethyl sulfoxide is used to extract and separate dimethyl carbonate, and at the same time, propylene oxide reacts with methanol to generate propylene glycol methyl ether (which belongs to an environmentally friendly organic solvent with a wide range of applications). The generated propylene glycol methyl ether can further promote the extraction separation process, making the extraction separation and reaction separation processes significantly more efficient. There is no need to use too much extractant, nor to set complex reaction conditions. High-purity methanol can be directly separated from the top of the extraction reactive distillation column. In addition, since the mixed liquid of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether can efficiently and quickly obtain high-purity dimethyl carbonate products during subsequent vacuum distillation; the separation method of dimethyl carbonate and methanol provided in this application achieves a high-efficiency online continuous separation effect, without setting complicated process conditions. The entrainer selected has a wide range of raw material sources, and the separation process has low energy consumption and reasonable operating costs, and is very suitable as a separation process for industrial implementation applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 is a block diagram of the operation steps of the separation method of dimethyl carbonate and methanol under the specific embodiment of the present invention;
[0026] Figure 2 is a schematic diagram of the device connection structure adopted by the separation method of dimethyl carbonate and methanol in Embodiment 1 of the present invention;
[0027] Figure 3 is a sample photo of the dimethyl carbonate product produced in Embodiment 1 of the present invention;
[0028] Figure 4 is a chromatogram of the dimethyl carbonate product produced in Embodiment 1 of the present invention (detected by gas chromatography SDMC, and the injection volume is 0.5 μL). DETAILED DESCRIPTION OF THE EMBODIMENTS
[0029] Please refer to Figure 1 as shown, this embodiment provides a separation method of dimethyl carbonate and methanol, including the following operation steps:
[0030] S10. Feed the azeotropic mixture of dimethyl carbonate and methanol and the mixture of dimethyl sulfoxide and propylene oxide into the azeotrope feed port and the mixture feed port of the extractive reactive distillation column 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 mixture of dimethyl sulfoxide and propylene oxide is 45-65% (more preferably 50-60%); the molar ratio of propylene oxide in the mixture 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 mixture 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 mixture feed port through a pipeline;
[0031] S20. In the extractive reactive distillation column filled with a catalyst, part of the methanol in the azeotropic mixture reacts with
[0032] propylene oxide in the mixture to form propylene glycol methyl ether; the mixture of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether is withdrawn from the bottom of the extractive reactive distillation column, and methanol is withdrawn from the top of the extractive reactive distillation column; preferably, in this step S20, the purity of the methanol withdrawn from the top of the extractive reactive distillation column is not less than 99% (usually higher than 99.7%), and it is connected to a methanol storage tank;
[0033] S30. Feed the mixture of dimethyl carbonate, dimethyl sulfoxide and propylene glycol methyl ether into a first distillation column for vacuum distillation. Dimethyl carbonate product is withdrawn from the top of the first distillation column, and the mixture of dimethyl sulfoxide and propylene glycol methyl ether is withdrawn from the bottom of the first distillation column; preferably, in this step S30, the purity of the dimethyl carbonate product withdrawn from the top of the first distillation column is not less than 99%, preferably greater than 99.9%, more preferably greater than 99.99%, and it is connected to a dimethyl carbonate product storage tank;
[0034] S40. Feed the mixture of dimethyl sulfoxide and propylene glycol methyl ether into a second distillation column for vacuum distillation. Propylene glycol methyl ether is withdrawn from the top of the second distillation column, and dimethyl sulfoxide is withdrawn from the bottom of the second distillation column; preferably, in this step S40, the purity of the propylene glycol methyl ether withdrawn from the top of the second distillation column is not less than 99%, and it is connected to a propylene glycol methyl ether storage tank; the purity of the dimethyl sulfoxide withdrawn from the bottom of the second distillation column is not less than 95%, more preferably not less than 97%; the dimethyl sulfoxide withdrawn from the bottom of the second distillation column is connected to the tube-in-tube mixer for recycling;
[0035] Preferably, in the present embodiment, in order to facilitate the separation effect of the separation process provided in this embodiment, in the present embodiment, the structure of the relevant device and the process parameter scheme are recommended to be set as follows:
[0036] The number of theoretical plates of the extractive reactive distillation column is 35 - 50; the feeding position of the azeotrope feed inlet is the 15th - 25th plate; the feeding position of the mixed liquid feed inlet is the 3rd - 6th plate; a first condenser is provided at the top of the extractive reactive distillation column, and a first reboiler is provided at its bottom; the tower pressure of the extractive reactive distillation column is 0.12 - 0.2 MPa; the tower bottom temperature of the extractive reactive distillation column is set to 90 - 105 °C, and the tower top temperature of the extractive reactive distillation column is set to 60 - 80 °C; the reflux ratio of the extractive reactive distillation column is set to 1 - 5;
[0037] The extractive reactive distillation column includes a rectifying section located above, a reaction section located in the middle, and a stripping section located below; a quaternary ammonium salt catalyst is filled in the reaction section;
[0038] Preferably, the number of theoretical plates of the first distillation column 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; a second condenser is provided at the top of the first distillation column, and a second reboiler is provided at its bottom; the tower pressure of the first distillation column is 0.05 - 0.08 MPa; the tower bottom temperature of the first distillation column is set to 105 - 120 °C, and the tower top temperature of the first distillation column is set to 80 - 100 °C; the reflux ratio of the first distillation column is set to 3 - 6;
[0039] Preferably, the number of theoretical plates of the second distillation column is 20 - 30; the feeding position of the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is the 10th - 12th plate; a third condenser is provided at the top of the second distillation column, and a third reboiler is provided at its bottom; the tower pressure of the second distillation column is 0.05 - 0.07 MPa; the tower bottom temperature of the second distillation column is set to 135 - 150 °C, and the tower top temperature of the second distillation column is set to 110 - 130 °C; the reflux ratio of the second distillation column is set to 3 - 6.
[0040] It should be particularly noted that in this application, through a large number of exploratory experiments, the above embodiments list various preferred range parameters, and those skilled in the art can select within these preferred parameter ranges (including endpoint values and intermediate values) according to the actual situation. For the sake of saving the space of the specification, these will not be elaborated one by one in this embodiment.
[0041] To enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1:
[0042] Please refer to Figure 2 As shown, the following devices are first selected to implement the separation process of Embodiment 1:
[0043] The number of theoretical plates of the extraction reactive distillation column 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; a first condenser 110 is provided at the top of the extraction reactive distillation column 100, and a first reboiler 120 is provided at its bottom; the tower pressure of the extraction reactive distillation column 100 is atmospheric pressure; the tower bottom temperature of the extraction reactive distillation column 100 is set at 95 °C, and the tower top temperature of the extraction reactive distillation column 100 is set at 70 °C; the reflux ratio of the extraction reactive distillation column 100 is set at 1.5; the extraction reactive distillation column 100 includes a rectifying section (from the top of the tower to the 17th plate) located above, a reaction section (from the 18th plate to the 30th plate) located in the middle, and a stripping section (from the 31st plate to the bottom of the tower) located below; a quaternary ammonium salt catalyst is filled in the reaction section;
[0044] The number of theoretical plates of the first distillation column 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 column 200, and a second reboiler 220 is provided at its bottom; the tower pressure of the first distillation column 200 is 0.06 MPa; the tower bottom temperature of the first distillation column 200 is set at 110 °C, and the tower top temperature of the first distillation column 200 is set at 90 °C; the reflux ratio of the first distillation column 200 is set at 4;
[0045] The number of theoretical plates of the second distillation column 300 is 25; the feeding position of the mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is the 12th plate; a third condenser 310 is provided at the top of the second distillation column 300, and a third reboiler 320 is provided at its bottom; the tower pressure of the second distillation column 300 is 0.06 MPa; the tower bottom temperature of the second distillation column 300 is set at 140 °C, and the tower top temperature of the second distillation column 300 is set at 120 °C; the reflux ratio of the second distillation column 300 is set at 3;
[0046] The purity of each material is detected by a chromatograph Agilent 7890A.
[0047] The operation of this Embodiment 1 is carried out according to the following steps:
[0048] (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 in a feeding mode with a mass ratio of 1:1 for static mixing, and a mixed solution of dimethyl sulfoxide and propylene oxide is obtained through mixing;
[0049] (2). The crude dimethyl carbonate output from the dimethyl carbonate synthesis production line (which is an azeotropic mixture of dimethyl carbonate and methanol, and the content of dimethyl carbonate is about 30%) is respectively fed into the mixed liquid feed port and the azeotrope feed port of the extraction reactive distillation column 100; the molar ratio between propylene oxide in the mixed liquid and methanol in the azeotropic mixture is 1:6;
[0050] (3). Inside the extraction reactive distillation column 100, all propylene oxide reacts with part of methanol to generate propylene glycol methyl ether. Both propylene glycol methyl ether and dimethyl sulfoxide serve as extraction agents to quickly separate dimethyl carbonate from the azeotropic mixture. A mixed liquid of dimethyl carbonate, dimethyl sulfoxide, and propylene glycol methyl ether is drawn from the bottom of the extraction reactive distillation column 100, and methanol is drawn from the top of the extraction reactive distillation column 100; through content detection, the purity of methanol is 99.91%, and it is connected to the methanol storage tank 410;
[0051] (4). The mixed liquid of dimethyl carbonate, dimethyl sulfoxide, and propylene glycol methyl ether is fed into the first distillation column 200 for vacuum distillation. Dimethyl carbonate product is drawn from the top of the first distillation column 200, and a mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is drawn from the bottom of the first distillation column 200; through content detection, the purity of the dimethyl carbonate product is greater than 99.99%, and the yield is about 93%. It is connected to the dimethyl carbonate product storage tank 400. Please refer to the sample photo shown in Figure 3 and the product chromatogram shown in Figure 4 ;
[0052] (5). The mixed liquid of dimethyl sulfoxide and propylene glycol methyl ether is fed into the second distillation column 300 for vacuum distillation. Propylene glycol methyl ether is drawn from the top of the second distillation column 300 and connected to the propylene glycol methyl ether storage tank 420; dimethyl sulfoxide is drawn from the bottom of the second distillation column 300; through content detection, the purity of propylene glycol methyl ether is 99.98%, and the purity of dimethyl sulfoxide is 99.3%;
[0053] (6). The dimethyl sulfoxide drawn in the above step (5) is connected to the dimethyl sulfoxide feed pipeline of the tube mixer 500.
[0054] Example 2: The rest of the technical solutions in this Example 2 are the same as those in Example 1, except that in this Example 2, the number of theoretical plates of the extraction reactive distillation column 100 is 35; the feeding position of the azeotrope feed inlet is the 18th plate; the feeding position of the mixed liquid feed inlet is the 3rd plate; the tower pressure of the extraction reactive distillation column 100 is 0.13 MPa; the bottom temperature of the extraction reactive distillation column 100 is set at 100 °C, and the top temperature of the extraction reactive distillation column 100 is set at 75 °C; the reflux ratio of the extraction reactive distillation column 100 is set at 2.
[0055] Example 3: The rest of the technical solutions in this Example 3 are the same as those in Example 1, except that in this Example 3, the number of theoretical plates of the first distillation column 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 column 200 is 0.08 MPa; the bottom temperature of the first distillation column 200 is set at 115 °C, and the top temperature of the first distillation column 200 is set at 95 °C; the reflux ratio of the first distillation column 200 is set at 5.
[0056] Example 4: The rest of the technical solutions in this Example 4 are the same as those in Example 1, except that in this Example 4, the number of theoretical plates of the second distillation column 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 column 300 is 0.07 MPa; the bottom temperature of the second distillation column 300 is set at 145 °C, and the top temperature of the second distillation column 300 is set at 125 °C; the reflux ratio of the second distillation column 300 is set at 4.
[0057] Example 5: The rest of the technical solutions in this Example 5 are the same as those in Example 1, except that in this Example 5, dimethyl sulfoxide and propylene oxide are fed into the tube-sheet mixer 500 in a mass ratio of 1.3:1 for static mixing.
[0058] Example 6: The rest of the technical solutions in this Example 6 are the same as those in Example 1, except that in this Example 6, the molar ratio of propylene oxide in the mixed liquid to methanol in the azeotrope mixture is 1:5.
[0059] Example 7: The rest of the technical solutions in this Example 7 are the same as those in Example 1, except that in this Example 7, the molar ratio of propylene oxide in the mixed liquid to methanol in the azeotrope mixture is 1:7.
[0060] Comparative Example 1: The rest of the technical solutions in this Comparative Example 1 are the same as those in Example 1, except that in this Comparative Example 1, the tube-sheet mixer 500 is cancelled, the dimethyl sulfoxide feed pipeline is directly connected to the mixed liquid feed inlet of the extraction reactive distillation column 100, and the propylene oxide feed pipeline is not connected.
[0061] Comparative Example 2: The rest of the technical solutions of this Comparative Example 2 are the same as those of Example 1, except that in this Comparative Example 2, the tube bundle mixer 500 is cancelled, and the propylene oxide feed pipeline is directly connected to the mixed liquid feed port of the extraction reactive distillation column 100, without connecting to the dimethyl sulfoxide feed pipeline.
[0062] Comparative Example 3: The rest of the technical solutions of this Comparative Example 3 are the same as those of Example 1, except that in this Comparative Example 3, the tube bundle mixer 500 is cancelled, and the propylene oxide feed pipeline and the dimethyl sulfoxide feed pipeline are directly connected to the mixed liquid feed port of the extraction reactive distillation column 100 respectively.
[0063] Comparative Example 4: The rest of the technical solutions of this Comparative Example 4 are the same as those of Example 1, except that in this Comparative Example 4, propylene carbonate is used to replace dimethyl sulfoxide in Example 1, and it may react with propylene oxide to generate impurities.
[0064] Comparative Example 5: The rest of the technical solutions of this Comparative Example 5 are the same as those of Example 1, except that in this Comparative Example 5, water is used to replace dimethyl sulfoxide in Example 1.
[0065] Comparative Example 6: The rest of the 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 dimethyl sulfoxide in Example 1, but its miscibility with propylene oxide is poor, and it will cause a new azeotropic problem with methanol.
[0066] The applicant also separately conducted content detection on the relevant components obtained in Examples 2-7 and Comparative Examples 1-6. The detection results are shown in Table 1 below:
[0067]
[0068] Note: The " / " in Table 1 above means that it has been confirmed that the detection data of the relevant components in this comparative example do not meet the requirements, so subsequent detection of other components obtained in this comparative example was not carried out.
[0069] Through the implementation results of the above examples and comparative examples, it can be confirmed that the separation process of dimethyl carbonate and methanol provided by the examples of the present application achieves a high-efficiency online continuous separation effect, and there is no need to set complicated process conditions. The entrainer raw materials selected 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 applications.
[0070] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.
[0071] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments 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 solution of dimethyl sulfoxide and propylene oxide into the azeotropic feed port and the mixed solution feed port of the extractive reaction distillation tower respectively; in the step S10, the mixed solution 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 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 solution 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; in the step S20, the tower pressure of the extractive reaction distillation tower is 0.12-0.2MPa; the bottom temperature of the extractive reaction distillation tower is set to 90-105°C, and the 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 catalyst uses a quaternary ammonium salt catalyst; 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 solution 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; 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 99.99%, and it is connected to the dimethyl carbonate product storage tank.
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 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.
5. 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.
6. 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.
7. The method for separating dimethyl carbonate and methanol according to claim 1, 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.