Process and device for separating and purifying dimethyl carbonate

Abstract

The application discloses a separation and purification process of dimethyl carbonate in the technical field of petroleum chemical industry, and is characterized by comprising the following steps: 1) feeding crude DMC into a DMC pre-separation tower, wherein the product at the tower bottom is heavy components, the product at the tower top is light components, and the product at the side line is DMC containing trace methanol; 2) feeding the product at the side line of the DMC pre-separation tower into a DMC refining tower, wherein the product at the tower bottom is high-purity DMC, and the product at the tower top is DMC-methanol azeotrope. The application can reduce the generation of DMC-methanol azeotrope, thereby reducing production energy consumption and equipment investment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical separation, and particularly relates to a production device and process for separating dimethyl carbonate from a gaseous mixture system of light components, methanol, dimethyl carbonate and heavy components. TECHNICAL BACKGROUND

[0002] Dimethyl carbonate (DMC) is a new green chemical product which has been widely concerned in recent years. As an organic chemical intermediate, DMC has good chemical reaction activity due to the methyl, methoxy and carbonyl methoxy groups in its molecule. Because DMC is non-toxic, it can replace the methylating agents or carbonyl agents such as phosgene, methyl chloroformate and dimethyl sulfate, and produce a variety of fine chemicals, improve the safety of production operation and reduce environmental pollution. As a solvent, DMC has good anti-static effect due to its large surface tension, low viscosity and small dielectric constant, and can be widely used as an electrolyte solvent for lithium ion batteries. As a gasoline additive, DMC can replace methyl tert-butyl ether (MTBE) to enhance the anti-knock performance of gasoline. Because DMC has a wide range of applications in pesticides, medicines, polymer synthesis, fuel additives and solvents, it is known as the "new cornerstone" of organic synthesis in the 21st century.

[0003] At present, the main production methods of DMC include phosgene method, methanol oxidation carbonyl method, ester exchange method and CO esterification method. The phosgene method has been basically eliminated due to serious environmental pollution, and the reaction products of the latter three methods all contain methanol. Because DMC and methanol can form an azeotropic mixture, it is difficult to meet the product quality requirements by using conventional separation methods. Therefore, the reported DMC separation methods all focus on the separation of DMC-methanol azeotrope, and the main methods include pressure swing distillation, extractive distillation, azeotropic distillation, adsorption and membrane separation.

[0004] Chinese patent CN200710064633 discloses a membrane separation method, which uses the different permeation selectivity of the membrane to dimethyl carbonate and methanol to realize the separation of DMC-methanol azeotrope. However, the membrane separation method device has high maintenance cost, and it is difficult to meet the requirements of large-scale industrial production. Patent CN20131009817.7 discloses an extractive distillation method, which uses ethylene glycol as an extractant, and the DMC-methanol mixture is fed in the middle of the extractive distillation column, the extractant is fed at the top of the column, high-purity MeOH is collected at the top of the column, and DMC and the extractant are collected at the bottom of the column; the bottom fraction is fed into the extractant recovery column, DMC is collected at the top of the column, and the extractant is collected at the bottom of the column for recycling. The extractive distillation method needs to introduce new substances into the system, which affects the product purity, and also needs to increase an extractant recovery column, the operation process is complex, and the energy consumption for recovering the extractant is also high. The pressure swing distillation method is most widely used in the industrial application of separating DMC-methanol mixture, but the energy consumption is high, and the investment in high-pressure equipment is large. The pressure swing distillation method disclosed in CN1271721A performs heat integration between the pressurized distillation column and the atmospheric distillation column, which can reduce the energy consumption of the pressure swing distillation process to a certain extent, but the recovery rate of dimethyl carbonate is low, and the design pressure of the pressurized distillation column is also too high.

[0005] It can be seen that for the separation of DMC-methanol azeotrope, it is difficult to realize the production requirements of low investment and low energy consumption no matter which method is used, so the key to optimizing the DMC separation process lies in reducing the generation of DMC-methanol azeotrope. SUMMARY

[0006] To solve the above problems, the present application provides a dimethyl carbonate separation and purification device and process, which reduces the generation of DMC-methanol azeotrope, thereby reducing the production energy consumption and equipment investment.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] A dimethyl carbonate separation and purification process, characterized by comprising the following steps: 1) feeding the crude DMC into a DMC pre-separation column, the product at the bottom of the column is heavy components, the product at the top of the column is light components, and the product at the side line is DMC containing a small amount of methanol;

[0009] 2) feeding the DMC pre-separation column side line product into a DMC refining column, the product at the bottom of the column is high-purity DMC, and the product at the top of the column is DMC-methanol azeotrope.

[0010] The application further relates to a DMC separation and purification process, which is characterized in that: in the DMC pre-separation tower, a gas-phase mixture containing light components, methanol, DMC and heavy components enters the DMC pre-separation tower from the middle part of the tower, is separated by rectification, the light components and methanol are collected from the top of the DMC pre-separation tower, the concentrated DMC carrying part of the light components such as methanol is collected from the side line of the DMC pre-separation tower, and the heavy components such as water and DMO are collected from the bottom of the DMC pre-separation tower.

[0011] The application further relates to a DMC separation and purification process, which is characterized in that: in the DMC pre-separation tower, a gas-phase mixture containing light components, methanol, DMC and heavy components enters the DMC pre-separation tower from the middle part of the tower, is separated by rectification, the light components and methanol are collected from the top of the DMC pre-separation tower, the concentrated DMC carrying part of the light components such as methanol is collected from the side line of the DMC pre-separation tower, and the heavy components such as water and DMO are collected from the bottom of the DMC pre-separation tower.

[0012] The application further relates to a DMC separation and purification process, which is characterized in that: the number of plates of the DMC pre-separation tower is 50-150, and the number of plates of the DMC refining tower is 20-60.

[0013] The application further relates to a DMC separation and purification process, which is characterized in that: the top pressure of the DMC pre-separation tower is 0.1-0.5 MPag, and the top pressure of the DMC refining tower is 0.3-1.0 MPag.

[0014] The application further relates to a DMC separation and purification process, which is characterized in that: the top temperature of the DMC pre-separation tower is-5-40 DEG C, and the top temperature of the DMC refining tower is 50-120 DEG C.

[0015] The application further relates to a DMC separation and purification process, which is characterized in that: the bottom temperature of the DMC pre-separation tower is 120-200 DEG C, and the bottom temperature of the DMC refining tower is 120-200 DEG C.

[0016] The application further relates to a DMC separation and purification process, which is characterized in that: the mass purity of the DMC product in the bottom of the DMC refining tower is greater than 99.5%, the content of methanol in the product is less than 0.05%, and the content of water is less than 0.10%.

[0017] The application further provides a DMC separation and purification device, which comprises a DMC pre-separation tower and a DMC refining tower, a condenser and a tower top reflux tank are arranged at the top of the DMC pre-separation tower and the DMC refining tower, a reboiler is arranged at the bottom of the DMC pre-separation tower and the DMC refining tower, and a side line is arranged on the DMC pre-separation tower.

[0018] The application further has the features that the number of plates of the DMC pre-separation tower is 50-150, and the number of plates of the DMC refining tower is 20-60.

[0019] Compared with the prior art, the application has the advantages that:

[0020] 1) The crude DMC is not directly subjected to azeotrope separation, but is first subjected to the DMC pre-separation tower and the DMC refining tower, so that a high-purity DMC product can be obtained.

[0021] 2) The yield of the high-purity DMC product is as high as 90%, and less than 10% of the DMC forms a DMC-methanol azeotrope, so that the processing load of the azeotrope separation part is significantly reduced, the overall energy consumption and equipment investment are reduced, and compared with the pressure swing rectification process in which the crude DMC is directly subjected to azeotrope separation, the energy consumption can be reduced by 80%.

[0022] 3) The DMC pre-separation tower is provided with a side line for extraction, so that one rectification tower and its associated condensing system, reboiling system and material conveying pump are reduced, the process is simplified, the land occupation is saved, and the equipment investment is reduced.

[0023] 4) By adjusting the overhead temperature of the DMC pre-separation tower and the amount of extraction of the side line, the yield of the high-purity DMC product can be adjusted, which is beneficial to the stable operation of the device and increases the flexibility of the operation of the device.

[0024] The application will be further described in detail below in combination with the drawings and specific embodiments, but the use range of the application is not limited. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The application is a structure diagram of a DMC separation and purification device.

[0026] The signs shown in the drawings are as follows: 1-DMC pre-separation tower, 2-DMC pre-separation tower overhead condenser, 3-DMC pre-separation tower overhead reflux tank, 4-DMC pre-separation tower overhead reflux pump, 5-DMC pre-separation tower side line pump, 6-DMC pre-separation tower reboiler, 7-DMC pre-separation tower bottom pump, 8-DMC refining tower, 9-DMC refining tower overhead condenser, 10-DMC refining tower overhead reflux tank, 11-DMC refining tower overhead reflux pump, 12-DMC refining tower reboiler, 13-DMC refining tower bottom pump, 14-crude DMC raw material, 16-light component, 17-heavy component, 18-DMC-methanol azeotrope, and 19-high-purity DMC product. DETAILED DESCRIPTION

[0027] The application will be further described in combination with the drawings.

[0028] As shown in the drawings, Figure 1As shown, a kind of separation and purification device of dimethyl carbonate, including DMC pre-separation tower 1, DMC refining tower 8, and its attached DMC pre-separation tower top condenser 2, DMC pre-separation tower top reflux tank 3, DMC pre-separation tower top reflux pump 4, DMC pre-separation tower side line pump 5, DMC pre-separation tower reboiler 6, DMC pre-separation tower bottom pump 7, DMC refining tower top condenser 9, DMC refining tower top reflux tank 10, DMC refining tower top reflux pump 11, DMC refining tower reboiler 12 and DMC refining tower bottom pump 13.

[0029] Crude DMC raw material 14 is introduced into the middle part of DMC pre-separation tower 1, and the gas phase at the top of the tower is condensed after passing through DMC pre-separation tower top condenser 2 and enters DMC pre-separation tower top reflux tank 3 for vapor-liquid separation, and the gas phase product at the top of DMC pre-separation tower top reflux tank 3 is light component 16, and the liquid phase at the bottom of the tank returns to the top of DMC pre-separation tower 1 as reflux through DMC pre-separation tower top reflux pump 4. The side line product of DMC pre-separation tower 1 is DMC containing trace amounts of methanol and other light components, which is extracted by DMC pre-separation tower side line pump 5 after being pressurized and introduced into the upper part of DMC refining tower. DMC pre-separation tower reboiler 6 is arranged at the bottom of DMC pre-separation tower 1, and the tank product is heavy component 17, which is sent out by DMC pre-separation tower bottom pump 7. The gas phase at the top of DMC refining tower 8 is condensed after passing through DMC refining tower top condenser 9 and enters DMC refining tower top reflux tank 10 for vapor-liquid separation, and the gas phase product at the top of DMC refining tower top reflux tank 10 is a small amount of DMC-methanol azeotrope 18, and the liquid phase at the bottom of the tank returns to the top of DMC refining tower 8 as reflux through DMC refining tower top reflux pump 11. DMC refining tower reboiler 12 is arranged at the bottom of DMC refining tower 8, and the tank product is high-purity DMC product 19, which is sent out by DMC refining tower bottom pump 13.

[0030] A separation and purification device and process of dimethyl carbonate, the composition of crude DMC gas phase mixture from DMC synthesis reactor is (mass fraction): light component 82.5%, methanol 2.8%, DMC 14.1%, heavy component 0.6%, the above mixture is separated by the device and process proposed in the application.

[0031] The theoretical plate number of DMC pre-separation tower is 80, the top pressure is 0.2 MPag, the top temperature is 15℃, and the bottom temperature is 140℃. The mass concentration of DMC in the side line product is 93%, and the mass concentration of methanol is 5%.

[0032] The theoretical plate number of DMC refining tower is 20, the top pressure is 0.5 MPag, the top temperature is 100℃, and the bottom temperature is 160℃. The mass purity of DMC product at the bottom of the tower is greater than 99.5%, the content of methanol in the product is less than 0.05%, the content of water is less than 0.10%, and the yield of DMC product is 89%. The device process is simple, easy to operate, and conducive to industrial application.

Claims

1. A process for the separation and purification of dimethyl carbonate, characterized in that, Comprise the following steps: 1) feed the crude DMC into the DMC pre-separation column, the column bottom product is heavy components, the column top product is light components, and the side product is DMC containing trace methanol; 2) feed the DMC pre-separation column side product into the DMC refining column, the column bottom product is high purity DMC, and the column top product is DMC-methanol azeotrope.

2. The process for the separation and purification of dimethyl carbonate according to claim 1, characterized in that: In the DMC pre-separation column, the gas phase mixture containing light components, methanol, DMC, and heavy components enters the DMC pre-separation column from the middle part of the column, is separated by rectification, the light components and methanol are taken out from the column top of the DMC pre-separation column, the concentrated DMC carrying part of the light components such as methanol is taken out from the side line of the DMC pre-separation column, and the water, DMO and other heavy components are taken out from the column bottom of the DMC pre-separation column.

3. The process for separating and purifying dimethyl carbonate according to claim 1, characterized by: In the DMC refining column, the concentrated DMC carrying part of the light components such as methanol enters the DMC refining column from the upper part of the column, is separated by rectification, a small amount of DMC-methanol azeotrope is taken out from the column top of the DMC refining column, and the refined DMC containing trace methanol is taken out from the column bottom of the DMC refining column.

4. The process for separating and purifying dimethyl carbonate according to claim 1, characterized by: The number of plates of the DMC pre-separation column is 50-150, and the number of plates of the DMC refining column is 20-60.

5. The process for separating and purifying dimethyl carbonate according to claim 1, characterized by: The column top pressure of the DMC pre-separation column is 0.1-0.5 MPag, and the column top pressure of the DMC refining column is 0.3-1.0 MPag.

6. The process for separating and purifying dimethyl carbonate according to claim 1, characterized by: The column top temperature of the DMC pre-separation column is -5-40℃, and the column top temperature of the DMC refining column is 50-120℃; the column bottom temperature of the DMC pre-separation column is 120-200℃, and the column bottom temperature of the DMC refining column is 120-200℃.

7. The process for separating and purifying dimethyl carbonate according to claim 1, characterized by: The mass purity of the DMC product from the column bottom of the DMC refining column is greater than 99.5%, the content of methanol in the product is less than 0.05%, and the content of water is less than 0.10%.

8. A DMC separation and purification device, comprising a DMC pre-separation column and a DMC refining column, a condenser and a column top reflux tank are arranged at the column top of the DMC pre-separation column and the DMC refining column; a reboiler is arranged at the column bottom of the DMC pre-separation column and the DMC refining column; a side line is arranged in the DMC pre-separation column.

9. The device for separating and purifying dimethyl carbonate according to claim 8, characterized by: The number of plates of the DMC pre-separation column is 50-150, and the number of plates of the DMC refining column is 20-60.

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