阅读说明：本技术 一种甲醇和碳酸二甲酯共沸物连续分离方法 (Continuous separation method of methanol and dimethyl carbonate azeotrope ) 是由 刘勇军 王旭 黄伟 武海涛 刘甜甜 冯翀 潘丽 李伟斌 于 2021-01-25 设计创作，主要内容包括：一种甲醇和碳酸二甲酯共沸物连续分离方法,属于化工技术领域。它主要解决现有的普通精馏技术能耗及投资成本过高的问题。其特征是将萃取剂、共沸物分别从回流比为1～3,塔顶温度为60～150℃,塔底温度为140～260℃的分隔壁式精馏塔的上半部和中部进料,在压力为0.3～0.8 MPa的条件下进行萃取精馏；碳酸二甲酯和甲醇的混合液中碳酸二甲酯的质量分数为20～75%；萃取剂与甲醇和碳酸二甲酯的混合液的重量比为0.5～1.1。本发明具有设备少,投资小,能耗费用和操作费用低的优点。(A continuous separation method of an azeotrope of methanol and dimethyl carbonate belongs to the technical field of chemical industry. The method mainly solves the problems of high energy consumption and high investment cost of the existing common rectification technology. The method is characterized in that an extracting agent and an azeotrope are fed from the upper half part and the middle part of a dividing wall type rectifying tower with the reflux ratio of 1-3, the temperature at the top of the tower of 60-150 ℃ and the temperature at the bottom of the tower of 140-260 ℃ respectively, and are subjected to extractive distillation under the condition that the pressure is 0.3-0.8 MPa; the mass fraction of the dimethyl carbonate in the mixed liquid of the dimethyl carbonate and the methanol is 20-75%; the weight ratio of the extracting agent to the mixed liquid of the methanol and the dimethyl carbonate is 0.5-1.1. The invention has the advantages of less equipment, less investment, low energy consumption and operation cost.)

1. A continuous separation method of an azeotrope of methanol and dimethyl carbonate is characterized in that a mixed solution of an extracting agent, methanol and dimethyl carbonate is fed into an upper half part and a middle part of a dividing wall type rectifying tower respectively at a reflux ratio of 1-3, a tower top temperature of 60-150 ℃ and a tower bottom temperature of 140-260 ℃, and is subjected to extractive distillation under the condition that the pressure is 0.3-0.8 MPa; the mass fraction of the dimethyl carbonate in the mixed liquid of the dimethyl carbonate and the methanol is 20-75%; the weight ratio of the extracting agent to the mixed liquid of the methanol and the dimethyl carbonate is 0.5-1.1.

2. The method for continuously separating the azeotrope of methanol and dimethyl carbonate as claimed in claim 1, wherein the dividing wall type rectifying tower comprises an extractive distillation section, a rectification separation section and a common stripping section, the extractive distillation section and the rectification separation section are located at the upper part of the tower body of the dividing wall type rectifying tower, the extractive distillation section and the rectification separation section are separated by adopting a tower plate, and the common stripping section and the extractive distillation section and the rectification separation section are separated by adopting a tower plate; high-purity methanol is extracted from the top of the extraction and rectification section, and pure dimethyl carbonate is extracted from the top of the rectification and separation section.

3. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the extractant is ethylene glycol or benzene or a mixture of ethylene glycol and benzene, and the mass fraction of ethylene glycol in the mixture of ethylene glycol and benzene is 1-99%.

4. The method for continuously separating the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the number of the extractive distillation section plates of the dividing wall type distillation column is 20-50, and the number of the distillation separation section plates is 10-25.

5. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the azeotrope is 300kg/h, wherein the methanol content is 37 wt.%, the dimethyl carbonate content is 63 wt.%, the operating pressure is 0.3MPa, the ethylene glycol content is 130kg/h, the reflux ratio is 1.5, the overhead temperature is 100 ℃, the bottom temperature is 200 ℃, the number of the extractive distillation stage trays is 35, and the number of the rectification separation stage trays is 16; the separation result is: the purity of dimethyl carbonate was 99.9%, the recovery rate was 99.8%, the purity of methanol was 99.7%, and the recovery rate was 99.8%.

6. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the azeotrope is 300kg/h, wherein the methanol content is 37 wt.%, the dimethyl carbonate content is 63 wt.%, the operating pressure is 0.3MPa, the amount of ethylene glycol is 130kg/h, the reflux ratio is 2.5, the overhead temperature is 110 ℃, the bottom temperature is 240 ℃, the number of the extractive distillation stage trays is 35, and the number of the rectification separation stage trays is 16; the separation result is: the purity of dimethyl carbonate was 99.8%, the recovery rate was 99.9%, the purity of methanol was 99.6%, and the recovery rate was 99.8%.

7. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the azeotrope contains 37 wt.% of methanol, 63 wt.% of dimethyl carbonate, 0.3MPa of operation pressure, 130kg/h of ethylene glycol, 1.5 of reflux ratio, 120 ℃ of top temperature, 200 ℃ of bottom temperature, 35 of extractive distillation stage trays and 16 of rectification separation stage trays; the separation result is: the purity of dimethyl carbonate was 99.9%, the recovery rate was 99.9%, the purity of methanol was 99.7%, and the recovery rate was 99.8%.

8. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the azeotrope is 300kg/h, wherein the methanol content is 37 wt.%, the dimethyl carbonate content is 63 wt.%, the operating pressure is 0.5MPa, the benzene content is 130kg/h, the reflux ratio is 1.5, the overhead temperature is 130 ℃, the bottom temperature is 210 ℃, the number of the extractive distillation stage trays is 40, and the number of the rectification separation stage trays is 20; the separation result is: the purity of dimethyl carbonate was 99.7%, the recovery rate was 99.8%, the purity of methanol was 99.8%, and the recovery rate was 99.9%.

9. The continuous separation method of the azeotrope of methanol and dimethyl carbonate according to claim 1, wherein the azeotrope is 250 kg/h, wherein the methanol content is 50 wt.%, the dimethyl carbonate content is 50 wt.%, the operating pressure is 0.3MPa, the benzene content is 150 kg/h, the reflux ratio is 1.5, the overhead temperature is 60 ℃, the bottom temperature is 250 ℃, the number of the extractive distillation stage trays is 30, and the number of the rectification separation stage trays is 20; the separation result is: the purity of DMC was 99.9%, the recovery was 99.9%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Technical Field

The present invention relates to a continuous separation method of dimethyl carbonate and methanol, and more particularly, to a method of separating methanol and dimethyl carbonate under pressure using a dividing wall extraction column.

Background

The production process of Ethylene Glycol (EG) from coal mainly comprises the steps of generating dimethyl oxalate (DMO) through oxidative coupling, and then hydrogenating the DMO to obtain the ethylene glycol. In the process of synthesizing DMO, methyl nitrite and CO react on a catalyst in a gas phase to generate DMO, and a side reaction is simultaneously generated to generate dimethyl carbonate (DMC), while external methanol which is not completely reacted easily forms an azeotrope with generated DMC, so that the separation is difficult. The byproducts are mainly sold in the form of fusel oil, the unit price is low, and the economic benefit of enterprises is reduced. At present, due to the annual loss of the coal-based glycol, the improvement of the competitiveness and the economic benefit of enterprises becomes the primary target of the enterprises, and the acquisition of DMC with higher purity and higher added value by separating and refining byproducts becomes the focus of attention of the glycol industry.

DMC molecular Structure (CH)₃O₂C = O), is colorless and transparent, slightly odorous and slightly sweet liquid at normal temperature, has the characteristics of low toxicity, excellent environmental protection performance and the like, has the molecular weight of 90.08, the relative density of 1.065, the melting point of 4 ℃ and the boiling point of 90.1 ℃, can be mutually dissolved with organic solvents such as alcohol, ether, ketone and the like, and is a chemical raw material with wide application. The molecule contains a plurality of functional groups such as methyl, carbonyl, methoxyl and the like, so that the catalyst has good chemical reaction activity. DMC can also be used as an oil additive, not only to improve engine efficiency, but also to reduce NO _x CO, smoke particle emission. The DMC also has good physical properties such as good intermiscibility, high dielectric constant, low viscosity and the like, and the DMC is added into the lithium ion battery electrolyte, so that the battery has high current density and good oxidation reduction resistance, the service life of the battery is prolonged, and the demand on the battery grade DMC is increased along with the rapid development of new energy industries in recent years.

The methods commonly used at present for separating the binary azeotropic mixture methanol and DMC are as follows: azeotropic distillation, pressure swing distillation, extractive distillation, membrane separation and low temperature crystallization. For example, patents CN200610169592.5, CN200710064633, CN200710121912 and CN201310034796 disclose the use of membrane separation technology to separate the mixed solution of methanol and DMC, however, the purity of the obtained substance is not high, and further purification by conventional rectification is required. Patents CN109422647A, CN107915640A, CN107915642A and CN109422648A disclose a series of extractive distillation methods, but basically all the methods are based on common two-tower or three-tower distillation to purify, which will inevitably result in more tower equipment, large investment and high energy consumption.

Some documents report that the azeotrope of DMC and methanol is separated by azeotropic multi-tower distillation modes such as pressurization-depressurization, etc., wherein the depressurization requires a vacuum pumping system, and the pressurization increases the manufacturing cost of tower equipment, has high investment and has the problem of complicated operation.

In conclusion, the existing separation technology has the problems of low efficiency, high investment and high energy consumption, and along with the expansion of the capacity of producing ethylene glycol by coal in China, the existing separation technology of methanol and DMC azeotrope needs to be improved and innovated urgently, so that the separation cost is reduced, and the competitiveness of enterprises is improved.

Disclosure of Invention

The invention aims to solve the technical problems of high investment cost, low efficiency and high energy consumption of the existing separation technology, and provides a method for continuously separating an azeotrope of methanol and dimethyl carbonate.

In order to solve the problems, the invention adopts the following modes: a continuous separation method of an azeotrope of methanol and dimethyl carbonate takes a dividing wall type rectifying tower as a separation device, and the mixed liquid of an extracting agent, methanol and DMC is respectively fed from the upper half part and the middle part of the dividing wall type rectifying tower, and meanwhile, the extraction and the rectification are carried out under the condition that the pressure is 0.3-0.8 MPa.

In the technical scheme, the separation device is a dividing wall type rectifying tower.

In the technical scheme, the mixture of the methanol and the dimethyl carbonate enters from the middle part of the extraction and rectification section, the extractant enters from the upper half part of the extraction and rectification section, high-purity methanol is extracted from the top of the extraction and rectification section, pure DMC is extracted from the top of the rectification and separation section, and the extractant obtained from the tower bottom is recycled.

In the technical scheme, the mass fraction of DMC in the mixture of DMC and methanol is 20-75%.

In the technical scheme, the weight ratio of the extracting agent to the azeotropic mixed liquid is 0.5-1.1.

In the technical scheme, the extracting agent is ethylene glycol or benzene or a mixture of the ethylene glycol and the benzene. In the mixture of the glycol and the benzene, the mass fraction of the glycol accounts for 1-99%.

In the technical scheme, the reflux ratio of the dividing wall type rectifying tower is 1-3, the temperature of the top of the tower is 60-150 ℃, the temperature of the bottom of the tower is 140-260 ℃, the number of the tower plates of the extraction rectifying section is 20-50, and the number of the tower plates of the rectifying separation section is 10-25.

The method has the advantages of low energy consumption, small equipment investment, good separation effect and small occupied area.

Drawings

FIG. 1 is a schematic view of the internal structure of a divided wall type rectifying column according to the present invention.

In the figure, 1 is an extraction and rectification section, 2 is a rectification and separation section, and 3 is a public stripping section.

Detailed Description

The dividing wall type rectifying tower is composed of an extraction rectifying section 1, a rectifying separation section 2 and a public stripping section 3, wherein the extraction rectifying section 1 and the rectifying separation section 2 are positioned at the upper part of the dividing wall type rectifying tower body and account for 40-60% of the tower body volume, the extraction rectifying section 1 and the rectifying separation section 2 are isolated by adopting tower plates, and the public stripping section 3 and the extraction rectifying section 1 and the rectifying separation section 2 are isolated by adopting tower plates.

The invention is further illustrated by the following examples, without restricting the scope of the invention.

Example 1: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture is a mixture of methanol and dimethyl carbonate.

300kg/h of azeotropic mixed liquid, 37 wt.% of methanol, 63 wt.% of dimethyl carbonate, 0.3MPa of operating pressure, 130kg/h of extracting agent, 1.5 of reflux ratio, 100 ℃ of top temperature, 200 ℃ of bottom temperature, 35 of extractive distillation section trays and 16 of rectification separation section trays. The separation result is: the purity of DMC was 99.9%, the recovery was 99.8%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Example 2: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 300kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.3MPa, the extractant was ethylene glycol, the amount of the extractant was 130kg/h, the reflux ratio was 2.5, the top temperature was 110 ℃, the bottom temperature was 240 ℃, the number of extractive distillation stage trays was 35, and the number of rectification separation stage trays was 16. The separation result is: the purity of DMC was 99.8%, the recovery was 99.9%, the purity of methanol was 99.6%, and the recovery was 99.8%.

Example 3: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 300kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.3MPa, the extractant was ethylene glycol, the amount of the extractant was 130kg/h, the reflux ratio was 1.5, the top temperature was 120 ℃, the bottom temperature was 200 ℃, the number of extractive distillation stage trays was 35, and the number of rectification separation stage trays was 16. The separation result is: the purity of DMC was 99.9%, the recovery was 99.9%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Example 4: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 300kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.5MPa, the extractant was ethylene glycol, the extractant amount was 130kg/h, the reflux ratio was 1.5, the top temperature was 120 ℃, the bottom temperature was 200 ℃, the number of extractive distillation stage trays was 40, and the number of rectification separation stage trays was 16. The separation result is: the purity of DMC was 99.9%, the recovery was 99.8%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Example 5: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 300kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.5MPa, the extractant was ethylene glycol, the amount of the extractant was 130kg/h, the reflux ratio was 1.5, the top temperature was 130 ℃, the bottom temperature was 210 ℃, the number of extractive distillation stage trays was 40, and the number of rectification separation stage trays was 20. The separation result is: the purity of DMC was 99.9%, the recovery was 99.9%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Example 6: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 300kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.5MPa, the extractant was benzene, the amount of the extractant used was 130kg/h, the reflux ratio was 1.5, the top temperature was 130 ℃, the bottom temperature was 210 ℃, the number of plates in the extractive distillation section was 40, and the number of plates in the rectification separation section was 20. The separation result is: the purity of DMC was 99.7%, the recovery was 99.8%, the purity of methanol was 99.8%, and the recovery was 99.9%.

Example 7: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 400 kg/h, wherein the methanol content was 37 wt.%, the dimethyl carbonate content was 63 wt.%, the operating pressure was 0.5MPa, the extractant was benzene, the amount of extractant used was 230 kg/h, the reflux ratio was 1.5, the top temperature was 60 ℃, the bottom temperature was 250 ℃, the number of extractive distillation stage trays was 30, and the number of rectification separation stage trays was 20. The separation result is: the purity of DMC was 99.95%, the recovery was 99.9%, the purity of methanol was 99.9%, and the recovery was 99.9%.

Example 8: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 250 kg/h, wherein the methanol content was 50 wt.%, the dimethyl carbonate content was 50 wt.%, the operating pressure was 0.3MPa, the extractant was benzene, the extractant dosage was 150 kg/h, the reflux ratio was 1.5, the top temperature was 60 ℃, the bottom temperature was 250 ℃, the number of extractive distillation stage trays was 30, and the number of rectification separation stage trays was 20. The separation result is: the purity of DMC was 99.9%, the recovery was 99.9%, the purity of methanol was 99.7%, and the recovery was 99.8%.

Example 9: DMC and methanol were separated by extractive distillation using a dividing wall column as shown in FIG. 1. The process conditions are as follows: the azeotropic mixture was 250 kg/h, wherein the methanol content was 50 wt.%, the dimethyl carbonate content was 50 wt.%, the operating pressure was 0.5MPa, the extractant was ethylene glycol, the extractant dosage was 150 kg/h, the reflux ratio was 2.0, the top temperature was 80 ℃, the bottom temperature was 230 ℃, the number of extractive distillation stage trays was 40, and the number of rectification separation stage trays was 20. The separation result is: the purity of DMC was 99.97%, the recovery was 99.9%, the purity of methanol was 99.95%, and the recovery was 99.9%.

Comparative example 1: patent CN109422647A, CN107915640A and the like take ionic liquid as an extracting agent and a separating device is a common two-tower rectification separating azeotrope of DMC and methanol. Compared with the patent, the invention has the advantages of lower price of the extracting agent, less tower equipment and low cost.

Comparative example 2: adding organic base into the mixed solution and introducing high-pressure CO into the mixed solution, as in patent CN 109053448A₂Gas is stirred and filtered to obtain DMC, and then methanol, organic base and CO are obtained through further treatment₂And the like. Compared with the comparative example, the invention has the advantages of large treatment capacity per unit time, simple operation and higher DMC purity and recovery rate.