Process for refining battery fluid grade dimethyl carbonate through pressurization method coupled melt crystallization

Abstract

The invention relates to a process for refining battery fluid grade dimethyl carbonate from coal to ethylene glycol by-product dimethyl carbonate through pressurization method coupled melt crystallization. The process comprises the following steps: (1) materials are preheated: a coal to ethylene glycol product enters a normal-pressure T1 removal of light component tower, light components such as methylal and methyl formate are removed at the top of the T1 removal of light component tower, a part of dimethyl carbonate and dimethyl oxalate are removed at the bottom of the T1 removal of light component tower, side-draw produced methanol and DMC close to the upper part of a material inlet of the tower are mixed, and the mixed material enters a T2 pressurization tower; (2) a side-draw producedDMC azeotrope of the T1 tower enters the T2 pressurization tower, a DMC azeotrope with a DMC content of about 15-18% is obtained from the top of the pressurization rectification tower, and DMC with acontent of 99.5% or more is obtained from the tower kettle; and (3) dimethyl carbonate with a content of 99.5% enters a following film falling melt crystallization device, freezing is performed, sweating is performed, dissolving is performed, and therefore the battery fluid grade dimethyl carbonate with a content of 99.99% is obtained. The pressurization coupled melt crystallization separation process provided by the invention can remove more than 10 kinds of impurities in the coal to ethylene glycol by-product dimethyl carbonate, and the product quality reaches 99.99%, and the obtained dimethyl carbonate can be applied to prepare polycarbonate and a lithium battery fluid.

Description

technical field [0001] The invention belongs to chemical separation production technology, relates to the refining and recovery of by-products of coal-based ethylene glycol, and the preparation of polycarbon grade and battery liquid grade dimethyl carbonate, turning waste into wealth and benefiting the country and the people. Background technique [0002] Dimethyl carbonate is a colorless, transparent, slightly odorous, slightly sweet liquid at normal temperature and pressure. The relative density is 1.069, and the melting point is 2-4°C. The boiling point is 90°C. Insoluble in water. Dimethyl carbonate is a non-toxic, environmentally friendly and widely used chemical raw material. It is an important organic synthesis intermediate. Because its molecular structure contains carbonyl, methyl, methoxy and carbonylmethoxy, Therefore, it can be widely used in organic synthesis reactions such as carbonylation, methylation, methoxylation and carbonyl methylation. Because DMC is n...

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Problems solved by technology

[0008] The document "Separation Technology and Research of Coal-to-Ethylene Glycol by-product Dimethyl Carbonate" Chemical Management, Issue 1, 2018, this article is also coal-to-ethylene glycol, but its purpose of recycling dimethyl carbonate: 1. Reduce the synthesis system The content of dimethyl carbonate in the esterification tower ensures the methanol content in the esterification tower to ensure the complete reaction of the esterification system; 2. Although the dimethyl carbonate it draws is also through pressurized rectification, the pressurized rectification separates dimethyl carbonate , the content reaches 99.5%, which is already the limit, and there are still a small amount of impurities that cannot be removed by the retention method, so the dimethyl carbonate produced by the pressurized rectification method can only be used in low-end markets such as coatings. The required content of dimethyl ester is 99.9%, and the requirement of battery fluid grade dimethyl carbonate is 99.99%.

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