Preparation method of high-purity glycolic acid crystals

Abstract

The invention discloses a preparation method of high-purity glycolic acid crystals. The preparation method comprises the following steps of: (1) taking a 70% or below glycolic acid aqueous solution as a raw material, and firstly concentrating the glycolic acid aqueous solution to be of 70% or above under a low temperature vacuum condition; (2) slowly cooling and crystallizing the concentrated glycolic acid aqueous solution, and ensuring that crystal crude products are obtained through timely filtration at a low temperature; and (3) repeatedly washing the crystal crude products by an appropriate organic solvent, removing a small amount of glycolic acid low polymers from the crystals, and then drying the crystals at the low temperature to obtain the high-purity crystals. According to the preparation method, various traditional glycolic acid technical aqueous solution can be processed, the concentration requirement for the glycolic acid aqueous solution is low, the solution of below 70% can be above 70% by concentration so that the crystallization is facilitated; the crystals have high purity after being processed, are higher in yield and convenient for increasing the additional value of products; and the technology is simple and free of pollution.

Description

technical field [0001] The invention relates to a method for preparing high-purity glycolic acid crystals with a low-concentration glycolic acid aqueous solution as a raw material. Background technique [0002] Glycolic acid is an important organic synthesis intermediate and chemical product with a wide range of applications. As a new type of fine chemical intermediate, it is mainly used in the fields of cosmetics, cleaning agents, fungicides, new biodegradable materials and daily chemicals. [0003] Mention the method for the preparation of glycolic acid in the disclosed literature to have: the chloroacetic acid alkali hydrolysis of Japanese publication No. 9-21684 communique, concentrate, remove the point dialysis method of diluting with water after alkali metal chloride again, by this method Chloride ions in the obtained product are difficult to remove, thereby affecting the quality and application scope of the product. [0004] U.S. Patent No. 4,054,601 and Chinese Pat...

AI Technical Summary

Problems solved by technology

[0005] After the hydroxyacetonitrile disclosed in Chinese Patent Publication No. CN1724504A is hydrolyzed under acidic conditions, methanol is added for esterification, and the mixture of methanol, water and glycolic acid is steamed, and then water is added for hydrolysis to separate glycolic acid. The product with high purity should be obtained, but the disadvantage is that the esterification reaction time is long and the esterification rate is not high, resulting in low process yield and high energy consumption and high production cost.

[0006] Hydroxyacetonitrile disclosed in Chinese Patent No. CN1944379A is hydrolyzed in phosphoric acid, then concentrated and crystallized to remove salt, and concentrated acetone, water, glycolic acid mixture under reduced pressure. Using this method, the reaction time is long, the acetone is volatile and loses a lot, pollutes the environment, and costs Higher, easy to form peroxides in the distillation process, poor safety in large-scale industrial production

[0007] In the existing preparation and purification methods of glycolic acid, it is difficult to obtain high-purity glycolic acid crystal products. Even if a small part of traditional crystallization can obtain glycolic acid crystals, the yield is very low, and a large amount of mother liquor can only be used as low-grade products. Reduced product added value