阅读说明：本技术 一种电解液级碳酸二甲酯的制备方法 (Preparation method of electrolyte grade dimethyl carbonate ) 是由 骆念军 王磊 计扬 钱宏义 欧进永 于 2018-12-27 设计创作，主要内容包括：本发明涉及一种电解液级碳酸二甲酯的制备方法,含有CO、MN、NO和N<Sub>2</Sub>的混合气经过反应器(1)、气液分离器(2)、吸收塔(3)、DMO精馏塔(4)、常压精馏塔(5)和减压精馏塔(6)以后,可以采出高纯度的甲醇、草酸二甲酯以及电解液级碳酸二甲酯。与现有技术相比,本发明具有得到的产物种类少,产物分布简单,所得产品纯度高,色度小等优点。(The invention relates to a preparation method of electrolyte grade dimethyl carbonate, which contains CO, MN, NO and N 2 The mixed gas can be used for extracting high-purity methanol, dimethyl oxalate and electrolyte grade dimethyl carbonate after passing through a reactor (1), a gas-liquid separator (2), an absorption tower (3), a DMO rectifying tower (4), an atmospheric rectifying tower (5) and a reduced pressure rectifying tower (6). Compared with the prior art, the method has the advantages of few types of obtained products, simple product distribution, high purity of the obtained products, small chroma and the like.)

1. A preparation method of electrolyte-grade dimethyl carbonate is characterized in that mixed gas a containing CO and Methyl Nitrite (MN) reacts in a reactor (1) to generate a product containing dimethyl oxalate (DMO) and dimethyl carbonate (DMC), the product is separated by a gas-liquid separation tank (2), and an obtained liquid-phase product is separated to obtain the electrolyte-grade DMC.

2. The method for preparing dimethyl carbonate in electrolyte level according to claim 1, wherein the catalyst used in the reactor (1) comprises Pd as an active component and Al as a carrier₂O₃Or SiO₂The selectivity range of the catalyst adjustable DMC is 0.5-30%; the reaction temperature of the reactor (1) is 90-160 ℃, the absolute pressure is 0.15-0.4MPa, and the retention time is 0.5-10 s.

3. The method for preparing the electrolyte-grade dimethyl carbonate according to claim 1, wherein the temperature in the gas-liquid separation tank (2) is 20-80 ℃, the absolute pressure is 0.2-0.5MPa, and CH is contained in a liquid phase flowing out of the bottom of the gas-liquid separation tank (2)₄The mass content of O is 0.1-10%, the mass content of DMC is 0.5-20%, and the rest is DMO.

4. The method for preparing the electrolyte-grade dimethyl carbonate according to claim 1, wherein a gas-phase product discharged from the top of the gas-liquid separation tank (2) passes through an absorption tower (3), and DMO and DMC in the gas-phase product are absorbed by using liquid methanol A as an absorbent;

the mol ratio of the liquid methanol A entering the upper part of the absorption tower (3) to the gas phase product entering the lower part of the absorption tower (3) is 0.1-10: 1.

5. the preparation method of the electrolyte-grade dimethyl carbonate according to claim 4, characterized in that the excessive non-condensable gas b is discharged from the top of the absorption tower (3), the bottom liquid of the absorption tower (3) is mixed with the liquid-phase product at the bottom of the gas-liquid separation tank (2) and then enters a DMO rectifying tower (4) for separation, the top of the DMO rectifying tower (4) obtains a mixed solution of DMC and methanol, and the bottom of the DMO rectifying tower (4) obtains high-purity DMO;

the operation absolute pressure of the DMO rectifying tower (4) is 0.1-0.4MPa, the number of tower plates is 8-30, and the reflux ratio at the top of the tower is 2-7.

6. The method for preparing the electrolyte-grade dimethyl carbonate according to claim 5, wherein the mixed solution of DMC and methanol is fed into an atmospheric distillation tower (5), and the produced liquid at the bottom of the atmospheric distillation tower (5) is the electrolyte-grade dimethyl carbonate;

the operating absolute pressure of the atmospheric distillation tower (5) is 0.1-0.25MPa, the number of tower plates is 10-50, and the reflux ratio of the tower top is 2-13.

7. The preparation method of the electrolyte-grade dimethyl carbonate according to claim 6, wherein the produced liquid at the top of the atmospheric distillation tower (5) enters the vacuum distillation tower (6), the produced liquid at the top of the vacuum distillation tower (6) is circularly introduced to the upper part of the atmospheric distillation tower (5), and the produced liquid at the bottom of the vacuum distillation tower (6) is high-purity methanol;

the operating absolute pressure of the reduced pressure rectifying tower (6) is 20-202kPa, the number of the tower plates is 5-15, and the reflux ratio at the top of the tower is 2-10.

8. The method for preparing the electrolyte-grade dimethyl carbonate according to claim 7, wherein the mass ratio of the produced liquid at the top of the vacuum distillation tower (6) to the feed liquid entering the atmospheric distillation tower (5) is 0.01-0.5.

Technical Field

The invention relates to preparation of dimethyl carbonate, in particular to a preparation method of electrolyte grade dimethyl carbonate.

Background

Dimethyl carbonate (DMC) is a good methylating, carbonylating, hydroxymethylating and methoxylating agent and has very active chemical properties. As an organic synthesis intermediate, the compound is widely used for preparing low-boiling point solvents, cleaning agents, propellants and solvents for special paints. After deep processing, the product can be used as a gasoline additive, a high-energy battery electrolyte and a water treatment agent, and can be used for preparing polycarbonate, medicines, pesticides, spices, synthetic lubricating oil and the like. Is an ideal substitute for phosgene, dimethyl sulfate, methyl chloroformate and other highly toxic products, and is known as a green chemical product.

The dimethyl carbonate is produced by mainly adopting an ester exchange method in China, the quality of the product is continuously improved along with the continuous updating and perfection of the production process and the application of advanced equipment, the main content of all products of the dimethyl carbonate is more than or equal to 99.5 percent, the methanol is less than or equal to 0.2 percent, the water content is less than or equal to 0.01 percent, and the requirements of different customers at home and abroad can be met; meanwhile, the dimethyl carbonate is one of special solvents for the electrolyte of the lithium ion battery, and with the rapid development of the secondary battery, the demand of high-purity battery grade dimethyl carbonate is more and more increased. The main content of high-purity dimethyl carbonate in China currently reaches more than 99.9 percent, both moisture and methanol are less than 20ppm, the chroma is less than No. 5, and the battery grade DMC has great market potential and is the largest value-added space of the DMC industry.

Patent CN105272857A discloses a method for separating low-concentration dimethyl carbonate in the process of synthesizing dimethyl oxalate with coal-based syngas as raw material, but the method has the disadvantage that the absolute pressure is too high in the process of adopting double-tower flow, which not only causes the temperature of the feed liquid in the rectifying tower to be higher and causes higher energy consumption, but also causes esters in the tower kettle of the rectifying tower to be polymerized and generate waste products, and the obtained dimethyl carbonate has higher content of methanol, which cannot meet the requirements of battery-grade products.

Patent CN101462961A also discloses a process for synthesizing ethylene glycol and co-producing dimethyl carbonate from synthesis gas, but the problem is that battery grade dimethyl carbonate cannot be obtained and the yield is too low.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of electrolyte grade dimethyl carbonate. On one hand, the battery grade dimethyl carbonate is obtained, and the yield is improved; on the other hand, the energy consumption is reduced while the battery grade dimethyl carbonate with high yield is obtained.

The purpose of the invention can be realized by the following technical scheme:

a preparation method of electrolyte-grade dimethyl carbonate comprises the steps of enabling mixed gas a containing CO and Methyl Nitrite (MN) to react in a reactor (1) to generate a product containing dimethyl oxalate (DMO) and dimethyl carbonate (DMC), separating the product through a gas-liquid separation tank (2), and separating the obtained liquid-phase product to obtain the electrolyte-grade DMC.

Further, the active component of the catalyst used in the reactor (1) is Pd, and the carrier is Al₂O₃Or SiO₂The selectivity range of the catalyst adjustable DMC is 0.5-30%; the reaction temperature of the reactor (1) is 90-160 ℃, the absolute pressure is 0.15-0.4MPa, and the retention time is 0.5-10 s.

Further, the temperature in the gas-liquid separation tank (2) is 20-80 ℃, the absolute pressure is 0.2-0.5MPa, and CH is contained in the liquid phase flowing out of the bottom of the gas-liquid separation tank (2)₄The mass content of O is 0.1-10%, the mass content of DMC is 0.5-20%, and the rest is DMO.

Further, the gas-phase product discharged from the top of the gas-liquid separation tank (2) passes through an absorption tower (3), and DMO and DMC in the gas-phase product are absorbed by using liquid methanol A as an absorbent;

the mol ratio of the liquid methanol A entering the upper part of the absorption tower (3) to the gas phase product entering the lower part of the absorption tower (3) is 0.1-10: 1.

further, the excessive non-condensable gas b is discharged from the top of the absorption tower (3), the tower bottom of the absorption tower (3) and the liquid product at the bottom of the gas-liquid separation tank (2) are mixed and then enter a DMO rectifying tower (4) for separation, a mixed solution of DMC and methanol is obtained from the top of the DMO rectifying tower (4), and high-purity DMO is obtained from the tower bottom of the DMO rectifying tower (4);

the operation absolute pressure of the DMO rectifying tower (4) is 0.1-0.4MPa, the number of tower plates is 8-30, and the reflux ratio at the top of the tower is 2-7.

Further, the mixed solution of DMC and methanol enters a normal pressure rectifying tower (5), and the produced liquid at the tower bottom of the normal pressure rectifying tower (5) is electrolyte-grade dimethyl carbonate;

the operating absolute pressure of the atmospheric distillation tower (5) is 0.1-0.25MPa, the number of tower plates is 10-50, and the reflux ratio of the tower top is 2-13.

Further, the produced liquid at the top of the atmospheric distillation tower (5) enters a vacuum distillation tower (6), the produced liquid at the top of the vacuum distillation tower (6) is circularly introduced to the upper part of the atmospheric distillation tower (5), and the produced liquid at the bottom of the vacuum distillation tower (6) is high-purity methanol;

the operating absolute pressure of the reduced pressure rectifying tower (6) is 20-202kPa, the number of the tower plates is 5-15, and the reflux ratio at the top of the tower is 2-10.

Furthermore, the mass ratio of the produced liquid at the top of the vacuum distillation tower (6) to the feed liquid entering the atmospheric distillation tower (5) is 0.01-0.5.

Compared with the prior art, the invention takes CO and methyl nitrite as raw materials, the catalyst takes Pd as an active component, and the CO and the methyl nitrite react to synthesize the dimethyl oxalate and the dimethyl carbonate under the action of the catalyst, wherein the selectivity of the dimethyl carbonate in a reaction product can be adjusted by adjusting the catalyst. The product obtained by the process has few varieties and simple product distribution, and can be separated by a rectification operation unit to obtain a battery grade dimethyl carbonate product. The obtained battery grade dimethyl carbonate has the mass purity of more than 99.99 percent, the water content in the product is less than 10ppm, the methanol content is less than 5ppm, and the chroma is less than No. 5. The mass purity of the obtained dimethyl oxalate is more than 99.9 percent.

Drawings

FIG. 1 is a process flow diagram of an electrolyte grade DMC product.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.