Liquid-liquid extraction-azeotropic rectification mixing process for separating propylene glycol monomethyl ether and water

Abstract

The invention relates to a liquid-liquid extraction-azeotropic rectification mixing process for separating propylene glycol monomethyl ether and water. Firstly, a mixed extracting agent IS prepared byusing extracting agents 2-ethylhexoic acid and chloroform according to a certain ratio liquid-liquid extraction is performed on a propylene glycol methyl ether water solution, wherein the purity of the water in a raffinate phase at the top of a liquid-liquid extraction tower can reach more than 99.9 mol %, and an extraction phase is conveyed to an azeotropic rectification tower for azeotropic rectification. A phase separator is added to the upper part of the azeotropic rectification tower, water is collected from the upper part of the phase separator, chloroform is collected from the lower part of the phase separator for recycling the extracting agent, and a 2-ethylhexoic acid and propylene glycol monomethyl ether mixed solution at the bottom of the azeotropic rectification tower is conveyed to a recovery tower for separation. The product propylene glycol monomethyl ether is extracted from the top of the recovery tower, and the purity of the propylene glycol monomethyl ether is more than 99.9 mol %, and the extraction agent 2-ethylhexoic acid at the bottom of the tower is recycled. Devices mainly comprise the liquid-liquid extraction tower (LEC), the extraction rectifying tower (T1), the recovery tower (T2), a condenser (C1), a condenser (C2), a condenser (C3), a reflux tank (D1), a reboiler (R1), a reboiler (R2), a mixer (Mix), a flow divider (Fs) and a phase separator (DEC).

Description

【Technical field】 [0001] The invention belongs to the field of separation and purification in the chemical industry, and in particular relates to a liquid-liquid extraction-azeotropic rectification mixing process for separating propylene glycol methyl ether and water. 【Background technique】 [0002] Propylene glycol methyl ether (PM) is an important "universal solvent", dispersant, thinner, and can also undergo esterification with acetic acid to form one of the most commonly used esters with high industrial demand in surface coatings. Propylene glycol methyl ether Acetate, water are by-products of this reaction. Therefore, dehydration of propylene glycol methyl ether is an important and necessary operation. The separation process is the most energy-consuming link in industrial production. Propylene glycol methyl ether and water can form the lowest azeotrope, and ordinary distillation operations cannot achieve efficient separation. Therefore, it is of great significance to s...

AI Technical Summary

Problems solved by technology

The separation process is the most energy-consuming link in industrial production. Propylene glycol methyl ether and water can form the lowest azeotrope, and ordinary distillation operations cannot achieve efficient separation. Therefore, it is of great significance to seek a low-energy, high-efficiency separation method. Economic value and environmental benefits

[0003] There are binary azeotropes in the mixture of propylene glycol methyl ether and water, which cannot be effectively separated by ordinary rectification

[0004] Chinese patent CN107032966A discloses a recovery process of propylene glycol methyl ether. This process uses 2-ethylhexanoic acid as an extraction agent, and a large amount of water is removed with a liquid-liquid extraction tower and then separated by a rectification tower to obtain the finished product propylene glycol methyl ether. There is a problem with high energy consumption

However, the process is complicated to operate and only high-purity methanol can be obtained, and other mixtures are not separated and purified.

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