阅读说明：本技术 一种复合碱性离子液体催化连续生产碳酸二甲酯的方法 (Method for continuously producing dimethyl carbonate by catalysis of composite alkaline ionic liquid ) 是由 罗辉 邓文安 李传 杜峰 李庶峰 于 2021-09-07 设计创作，主要内容包括：本发明提供一种采用复合碱性离子液体为催化剂,经酯交换反应连续化生产碳酸二甲酯的方法,属于化学工业技术领域；将碳酸乙烯酯、甲醇和复合碱性离子液体经静态混合器进行混合并打入缓冲罐,混合物从缓冲罐打入反应精馏塔,进行酯交换反应,反应精馏塔顶产物经后续的加压精馏得到碳酸二甲酯产品和甲醇,甲醇打回到静态混合器循环使用,反应精馏塔底产物经后续的减压精馏得到乙二醇产品,碳酸乙烯酯和复合碱性离子液体的混合物打回到静态混合器循环使用。本发明与现有技术相比,复合碱性离子液体的催化活性高、稳定性好、易于分离,工艺流程简单、效率高、操作成本低,产品质量好。(The invention provides a method for continuously producing dimethyl carbonate by ester exchange reaction by using composite alkaline ionic liquid as a catalyst, belonging to the technical field of chemical industry; mixing ethylene carbonate, methanol and the composite alkaline ionic liquid through a static mixer and pumping the mixture into a buffer tank, pumping the mixture into a reaction rectifying tower from the buffer tank to perform ester exchange reaction, performing subsequent pressure rectification on a reaction rectifying tower top product to obtain a dimethyl carbonate product and methanol, pumping the methanol back to the static mixer for recycling, performing subsequent pressure rectification on a reaction rectifying tower bottom product to obtain an ethylene glycol product, and pumping the mixture of the ethylene carbonate and the composite alkaline ionic liquid back to the static mixer for recycling. Compared with the prior art, the composite alkaline ionic liquid has the advantages of high catalytic activity, good stability, easy separation, simple process flow, high efficiency, low operation cost and good product quality.)

1. A method for continuously producing dimethyl carbonate by catalysis of a composite alkaline ionic liquid is characterized in that ethylene carbonate or propylene carbonate, methanol and the alkaline ionic liquid are mixed through a static mixer and are injected into a buffer tank, the mixture is injected into a reaction rectifying tower from the buffer tank to carry out ester exchange reaction, an azeotrope of the methanol and the dimethyl carbonate is formed at the top of the reaction rectifying tower, a dimethyl carbonate product and the methanol are obtained through subsequent pressure rectification, and the methanol is injected back to the static mixer to be recycled; the bottom of the reactive distillation tower is a mixture of ethylene carbonate or propylene carbonate, ethylene glycol or propylene glycol and alkaline ionic liquid, ethylene glycol or propylene glycol products are obtained through subsequent vacuum distillation, and the mixture of ethylene carbonate or propylene carbonate and alkaline ionic liquid is pumped back to the static mixer for recycling;

wherein, the cation of the basic ionic liquid is a mixture of two or three of the following:

wherein n = 0-3;

the anion of the basic ionic liquid is a mixture of two or three of the following:

。

2. the production method according to claim 1, wherein the mixture in the buffer tank has a mass ratio of methanol to ethylene carbonate or propylene carbonate of (3-9): 1, and the basic ionic liquid accounts for 0.2-0.8 w% of the total mass of the mixture.

3. The production method according to claim 1, wherein the ester exchange reaction conditions in the reactive distillation column comprise a bottom temperature of 72-76 ℃, a top temperature of 63-64 ℃, a pressure of normal pressure, a reflux ratio of 1.0-3.0 and a reaction residence time of 5-30 min.

Technical Field

The invention relates to a method for producing dimethyl carbonate by using a transesterification method, in particular to a method for continuously producing dimethyl carbonate by using a composite alkaline ionic liquid as a catalyst, belonging to the technical field of chemical industry.

Background

Dimethyl carbonate (DMC) is an environment-friendly chemical intermediate, is an excellent green solvent, and is widely used for producing polycarbonate, paint, electrolyte, gasoline additives and the like. Functional groups such as carbonyl, methyl and the like in the dimethyl carbonate can carry out various potential chemical reactions, the carbonyl can replace toxic phosgene to be used as a carbonylation agent, the methyl can be used as a methylation agent to replace toxic and corrosive dimethyl sulfate and methyl halide, and the dimethyl carbonate is known as a new organic synthetic base stone at present.

The DMC preparation method mainly comprises a methanol oxidation carbonylation method, an ester exchange method, a urea alcoholysis method, an oxalate method and the like. The transesterification method is to obtain DMC by transesterification of cyclic carbonate such as Ethylene Carbonate (EC) or Propylene Carbonate (PC) with methanol, and has become the main method for industrial production of DMC due to its advantages of mild reaction conditions, high yield, low corrosivity, non-toxic process, etc. At present, EC (or PC) and methanol and a catalyst are mixed and then are injected into a rectification reaction tower for ester exchange reaction in industry, the tower top is an azeotrope of DMC and methanol, the azeotrope is subjected to pressure rectification to separate methanol and DMC, and the tower bottom of the rectification reaction tower is unreacted EC (or PC), ethylene glycol (or propylene glycol) and the catalyst. The catalyst adopted in the prior art is organic base, such as sodium methoxide, sodium ethoxide and the like. Sodium alkoxide on the one hand to water and CO₂The like is sensitive, so that the catalyst is easy to inactivate and form inorganic salts such as sodium carbonate and the like to be separated out, and the long-period operation of the device is influenced; on the other hand, sodium alkoxide and ethylene glycol (or propylene glycol) are difficult to separate, and many steps are required to separate the sodium alkoxide, so that the investment of the device is large, continuous production is difficult, and the quality of the ethylene glycol (or propylene glycol) is poor.

The ionic liquid has the advantages of wide liquid range, non-volatility, good stability, recyclability and the like, and the molecular structure has designability, is an excellent green solvent and catalyst, and is widely applied to the synthesis of DMC. The patent CN103980124B and the patent CN104043480A adopt quaternary ammonium salt ionic liquid to catalyze the transesterification reaction of PC and methanolThe ionic liquid of the synthesized dimethyl carbonate can be recycled, the process is simple, and the energy consumption of the product is low. The patent CN103055937B makes the ionic liquid immobilized on the surface of the pure silicon molecular sieve, and the immobilized ionic liquid can be recycled, has long service life and no pollution, and can effectively catalyze the ester exchange reaction of EC and methanol. Patent CN105237336B supports ionic liquid of imidazole cation and hydroxyl anion on chlorine-containing resin, and shows good performance in fixed bed catalysis of DMC synthesized by ester exchange of EC and methanol. Patent CN109704968A adopts [ DBUH ]][TFA]、[DBUH][TFE]、[DBUH]Cl、[TMGH][Im]、[n-Bu₄P][Im]The functionalized ionic liquids are used as catalysts, EC and methanol are subjected to ester exchange reaction to produce DMC, and the ionic liquid catalysts have the advantages of homogeneous reaction effect and heterogeneous catalyst, high catalytic activity, easy separation and recycling.

Disclosure of Invention

The invention aims to provide a method for continuously producing dimethyl carbonate by taking ethylene carbonate (or propylene carbonate) and methanol as raw materials, which takes composite alkaline ionic liquid as a catalyst, performs ester exchange reaction in a reaction rectifying tower, simultaneously separates dimethyl carbonate, methanol, ethylene carbonate (or propylene carbonate), ethylene glycol (or propylene glycol) and the catalyst, separates dimethyl carbonate from methanol by subsequent rectification, separates ethylene glycol (or propylene glycol) from ethylene carbonate (or propylene carbonate) and the catalyst, and recycles the ethylene carbonate (or propylene carbonate) and the catalyst. The method can effectively solve the problems that the sodium alkoxide catalyst is difficult to separate and affects continuous production in the prior art, and has the advantages of high production efficiency, simple process flow, low energy consumption, good product quality and the like.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

mixing ethylene carbonate (or propylene carbonate), methanol and composite alkaline ionic liquid through a static mixer and pumping the mixture into a buffer tank, pumping the mixture into a reaction rectifying tower from the buffer tank, carrying out ester exchange reaction under a certain condition, obtaining an azeotrope of the methanol and the dimethyl carbonate at the top of the reaction rectifying tower, carrying out subsequent pressurized rectification to obtain a dimethyl carbonate product and the methanol, and pumping the methanol back to the static mixer for recycling. The bottom of the reaction rectifying tower is a mixture of ethylene carbonate (or propylene carbonate), ethylene glycol (or propylene glycol) and composite alkaline ionic liquid, ethylene glycol (or propylene glycol) products are obtained through subsequent vacuum rectification, and the mixture of the ethylene carbonate (or propylene carbonate) and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The cation of the composite basic ionic liquid is a mixture of two or three of the following:

wherein n =0~3

The anion is a mixture of two or three of the following:

the mass ratio of methanol to ethylene carbonate (or propylene carbonate) in the mixture in the buffer tank is 3-9: 1, the composite alkaline ionic liquid accounts for 0.2-0.8 w% of the total mass of the mixture,

the ester exchange reaction conditions in the reactive distillation tower are that the temperature at the bottom of the tower is 72-76 ℃, the temperature at the top of the tower is 63-64 ℃, the pressure is normal pressure, the reflux ratio is 1.0-3.0, and the reaction residence time is 5-30 min.

The invention has the following beneficial effects:

(1) the catalytic activity of the composite alkaline ionic liquid is very high, the conversion rate of ethylene carbonate (or propylene carbonate) can reach more than 95%, and the selectivity of dimethyl carbonate is 100%.

(2) The composite alkaline ionic liquid is easy to separate, can be separated from a reaction system only by reduced pressure distillation, is easy for continuous production, and has the advantages of simple process flow, high efficiency, low energy consumption and good product quality.

(3) The composite alkaline ionic liquid has good stability, can be recycled and has low operation cost.

Detailed Description

The present disclosure is further explained or illustrated below by means of specific embodiments, but the examples should not be construed as limiting the scope of protection of the present disclosure.

Example 1:

mixing ethylene carbonate, methanol and composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the ethylene carbonate in the mixture is 3:1, and the composite alkaline ionic liquid accounts for 0.6 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 72 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 1.0, and the reaction residence time is 30 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of ethylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the ethylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of ethylene carbonate was 95.6% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, wherein the mass ratio of A to B is 3:1

The anion of the composite basic ionic liquid is a mixture of C, D, wherein the mass ratio of C to D is 1:1

Example 2:

mixing propylene carbonate, methanol and the composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the propylene carbonate in the mixture is 9:1, and the composite alkaline ionic liquid accounts for 0.8 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 76 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 3.0 and the reaction residence time is 5 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of propylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the propylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of propylene carbonate was 97.1% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, wherein the mass ratio of A to B is 1:1

The anion of the composite basic ionic liquid is a mixture of C, D, E, wherein the mass ratio of C to D to E is 4:4:2

Example 3:

mixing ethylene carbonate, methanol and composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the ethylene carbonate in the mixture is 6:1, and the composite alkaline ionic liquid accounts for 0.2 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 75 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 2.0, and the reaction residence time is 20 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of ethylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the ethylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of ethylene carbonate was 95.3% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, C, wherein the mass ratio of A to B to C is 1:1

The anion of the composite basic ionic liquid is a mixture of D, E, wherein the mass ratio of D to E is 4:1

Example 4:

mixing ethylene carbonate, methanol and composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the ethylene carbonate in the mixture is 8:1, and the composite alkaline ionic liquid accounts for 0.4 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 76 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 3.0 and the reaction residence time is 8 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of ethylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the ethylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of ethylene carbonate was 97.3% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, wherein the mass ratio of A to B is 3:1

The anion of the composite basic ionic liquid is a mixture of C, D, wherein the mass ratio of C to D is 4:1

Example 5:

mixing propylene carbonate, methanol and the composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the propylene carbonate in the mixture is 5:1, and the composite alkaline ionic liquid accounts for 0.5 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 76 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 2.0, and the reaction residence time is 20 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of propylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the propylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of propylene carbonate was 95.8% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, wherein the mass ratio of A to B is 1:1

The anion of the composite basic ionic liquid is a mixture of C, D, wherein the mass ratio of C to D is 4:1

Example 6:

mixing ethylene carbonate, methanol and composite alkaline ionic liquid through a static mixer, and pumping the mixture into a buffer tank, wherein the mass ratio of the methanol to the ethylene carbonate in the mixture is 8:1, and the composite alkaline ionic liquid accounts for 0.4 w% of the total mass of the mixture. The mixture is fed into a reaction rectifying tower from a buffer tank, and ester exchange reaction is carried out under the conditions that the temperature at the bottom of the tower is 76 ℃, the temperature at the top of the tower is 63.6 ℃, the pressure is normal pressure, the reflux ratio is 3.0 and the reaction residence time is 8 min. The top of the reactive distillation tower is an azeotrope of methanol and dimethyl carbonate, and the dimethyl carbonate product and the methanol are obtained through subsequent pressure distillation, and the methanol is pumped back to the static mixer for recycling. The bottom of the reactive distillation tower is a mixture of ethylene carbonate, ethylene glycol and composite alkaline ionic liquid, ethylene glycol products are obtained through subsequent vacuum distillation, and the mixture of the ethylene carbonate and the composite alkaline ionic liquid is pumped back to the static mixer for recycling.

The conversion per pass of ethylene carbonate was 97.6% and the selectivity to dimethyl carbonate was 100%.

The cation of the composite basic ionic liquid is a mixture of A, B, wherein the mass ratio of A to B is 1:1

The anion of the composite basic ionic liquid is a mixture of C, D, wherein the mass ratio of C to D is 1:1