PROCESS FOR PURIFYING CRUDE ACRYLIC ACID BY CRYSTALLIZATION

摘要

PURPOSE: A provided is a process for purifying by crystallization crude acrylic acid containing dibenzo-1,4- thiazine, the diacrylic acid content of the crude acrylic acid being set at a higher value before crystallization. CONSTITUTION: A process comprises the following steps of: increasing diacrylic acid content of crude acrylic acid by adding H2SO4, HCl, or H3PO4 which catalyze adding michael to acrylic acid or increasing temperature up to 5wt.%; producing acrylic acid esters by distilling and(or) fractional crystallizing crude acrylic acid; storing parts thereof and obtaining acrylic acid containing increased diacrylic acid therefrom; producing acrylic acid ester and pure acrylic acid by purifying crude acrylic acid containing benzo-1,4-thiazine by crystallization.