A dimethyl carbonate dehydration method for promoting hydrolysis and adsorbing methanol

Abstract

The present invention is a dimethyl carbonate dehydration method for promoting hydrolysis and absorbing methanol, which is characterized in that: the raw material liquid is passed through a bifunctional composite catalyst to hydrolyze DMC and absorb methanol; DMC is hydrolyzed with a trace amount of water under the action of an ester catalyst to produce methanol and CO 2 , CO 2 After being separated from DMC, it is discharged through the exhaust port; methanol is adsorbed on the absorption catalyst, thereby further promoting the hydrolysis of trace water in DMC and effectively removing DMC water and hydrolysis product methanol.

Description

Technical Field

[0001] The invention relates to the fields of chemical industry, energy conservation and environmental protection, and is a dimethyl carbonate dehydration method which promotes hydrolysis and adsorbs methanol. Background Art

[0002] Dimethyl carbonate (DMC, C3H6O3) is an environmentally friendly raw material widely used in the chemical industry. According to the People's Republic of China Nonferrous Metals Industry Standard YS / T 672-2008, the water and methanol content of battery-grade DMC must be less than 20 ppm. Removing methanol and trace water from DMC can be of great significance to the chemical industry and other fields.

[0003] Patent CN114272674A discloses a system for dehydrating dimethyl carbonate, the main feature of which is to use a dehydration tower to dehydrate and adsorb the raw material, and to use two dehydration towers alternately.

[0004] It can be seen from the announcement documents and existing technologies that, in addition to water, methanol, a hydrolysis product of DMC, is not removed. As long as DMC contains water, it will hydrolyze to produce methanol. If only the water in the water-containing DMC is removed, the product purity requirements cannot be met. For battery-grade DMC products with extremely low production water and methanol content, under conditions of extremely low water content, it is often necessary to combine distillation + adsorption to remove water, which consumes a lot of energy and equipment costs.

[0005] The following method is specially invented by using an ester hydrolysis catalyst to promote the hydrolysis of DMC and trace water, and using the adsorption of the hydrolysis product methanol to further promote the hydrolysis, and effectively remove DMC water and the hydrolysis product methanol. Summary of the invention

[0006] The present invention provides a dimethyl carbonate dehydration method for promoting hydrolysis and adsorbing methanol, which is characterized by:

[0007] The water content of crude DMC is ≤200ppm. It is passed through a bifunctional composite catalyst, which refers to a methanol adsorbent loaded with ester hydrolysis catalytic activity, and is used to hydrolyze DMC and absorb methanol. DMC is hydrolyzed with trace water under the action of the ester catalyst to produce methanol and CO2, which is separated from DMC and discharged through the exhaust port. Methanol is adsorbed on the adsorbent, thereby further promoting the hydrolysis of trace water in DMC, effectively removing DMC water and hydrolysis product methanol, and the water and methanol content in the dehydrated DMC reaches or exceeds battery-grade requirements.

[0008] Preferably, the ester hydrolysis catalyst includes but is not limited to metal oxides CuO, MgO and heteropolyacids; the methanol adsorbent includes but is not limited to molecular sieves, activated carbon, Al2O3-based and graphene-based catalysts.

[0009] The present invention utilizes the easy hydrolysis property of DMC, promotes the hydrolysis of DMC through a catalyst, and absorbs the hydrolysis product methanol to further promote the hydrolysis of DMC and trace water, so that dehydration and demethanolation complement each other and effectively remove the trace water and hydrolysis product methanol in DMC. DETAILED DESCRIPTION

[0010] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0011] Example 1: The raw material (water content 0.02%, methanol content 0.05%) is introduced into the CuO-Al2O3 catalyst absorption tower from the bottom, the alkaline catalyst CuO promotes the hydrolysis of DMC and trace water, the generated methanol is absorbed by the Al2O3-based adsorbent, and CO2 and DMC are separated and discharged through the exhaust port. The dehydrated and demethanolized DMC comes out from the top of the tower, and the water and methanol contents of the obtained finished product are both less than 20ppm.

[0012] Example 2: The raw material (water content 0.02%, methanol content 0.02%) is introduced into the MgO-Al2O3 catalyst absorption tower from the bottom, the alkaline catalyst MgO promotes the hydrolysis of DMC and trace water, the generated methanol is absorbed by Al2O3, CO2 and DMC are separated and discharged through the exhaust port. The dehydrated and demethanoled DMC comes out from the top of the tower, and the water and methanol contents of the obtained finished product are both less than 20 ppm.

[0013] Example 3: The raw material (water content 0.01%, methanol content 0.01%) is introduced into the phosphotungstic acid-Al2O3 catalyst absorption tower from the bottom. The phosphotungstic acid promotes the hydrolysis of DMC and trace water. The generated methanol is absorbed by the Al2O3-based catalyst. CO2 and DMC are separated and discharged through the exhaust port. The dehydrated and demethanolized DMC comes out from the top of the tower. The water and methanol contents of the obtained finished product are both less than 15 ppm.

[0014] Example 4: The raw material (water content 0.02%, methanol content 0.01%) is introduced into the CuO-graphene-based catalyst absorption tower from the bottom, the alkaline CuO promotes the hydrolysis of DMC and trace water, the generated methanol is absorbed by the graphene-based adsorbent, and CO2 and DMC are separated and discharged through the exhaust port. The dehydrated and demethanolized DMC comes out from the top of the tower, and the water and methanol contents of the obtained finished product are both less than 10ppm.

Claims

1. A method for dehydrating dimethyl carbonate by promoting hydrolysis and adsorbing methanol, characterized in that: The water content of crude DMC is ≤200ppm, and it is catalyzed and absorbed by a bifunctional composite catalyst, wherein the bifunctional composite catalyst refers to a methanol adsorbent loaded with an ester hydrolysis catalyst, which is used to hydrolyze DMC and absorb methanol; DMC is hydrolyzed with a trace amount of water under the action of the ester hydrolysis catalyst to produce methanol and CO2, which is separated from DMC and discharged through the exhaust port; Methanol is adsorbed on the adsorbent, thereby further promoting the hydrolysis of trace water in DMC, effectively removing water and hydrolysis product methanol in DMC, and the water and methanol content in the dehydrated DMC reaches or exceeds the battery grade requirements; in the bifunctional composite catalyst, the ester hydrolysis catalyst is CuO and MgO, and the methanol adsorbent is a molecular sieve, activated carbon, Al2O3-based and graphene-based catalyst; or the bifunctional composite catalyst is a phosphotungstic acid-Al2O3 catalyst.