Preparation method of high-purity glycolic acid crystals

A glycolic acid, high-purity technology, applied in the field of preparation of high-purity glycolic acid crystals, can solve the problems of reduced product added value, low esterification rate, low process yield, etc., to increase product added value, facilitate crystallization, process simple effect

Inactive Publication Date: 2013-03-13
SOUTHWEST RES & DESIGN INST OF CHEM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] Take 509.2g of 70% glycolic acid solution, the actual content is 65.71%, including some oligomers, and the water content is 31.06%, and it is concentrated by molecular distillation at an absolute pressure of 10 kPa and 50°C for 2 hours, and the concentration reaches 75.57%, and the water content is 13.06%. Slowly cool down to crystallize at a rate of 5°C / min. Every time the temperature drops by 10°C, let the temperature rise by 1°C and then continue to cool down. When the temperature drops to -5°C, a large number of crystals are precipitated, and 153g of crystals are obtained by pressure filtration. The purity of the crystals after low-temperature drying is 97.49%. , containing GA oligomers 3.50%. After the crystals were washed once with acetone, 83.9 g of crystals were obtained. After washing and drying at low temperature, the analytical purity was 98.64%. After the crystals were washed twice with acetone, 37.8 g of crystals were obtained, and the analytical purity afte...

Embodiment 2

[0030] Take 506.6g of 70% glycolic acid solution, the actual content is 65.71%, including some oligomers, and the water content is 31.06%, and it is concentrated by molecular distillation at an absolute pressure of 5 kPa and 40°C for 2 hours, and the concentration reaches 81.21%, and the water content is 9.62%. Slowly lower the temperature at a rate of 2°C / min to crystallize. Every time the temperature is lowered by 5°C, the temperature will rise by 1°C and then continue to cool down. When the temperature is lowered to -5°C, a large number of crystals are precipitated, and 195g of crystals are obtained by vacuum filtration. After low-temperature drying, the analytical purity of the crystals is 96.85. %, containing 3.13% of GA oligomers. After washing twice with ether, 168.2 g of crystals were obtained, and the analytical purity was 99.12% after drying at low temperature.

Embodiment 3

[0032] Take 508.1g of 70% glycolic acid solution, the actual content is 65.71%, including some oligomers, and the water content is 31.06%. It is concentrated by molecular distillation at an absolute pressure of 5 kPa and 20°C for 2 hours, and the concentration reaches 75%, and the water content is 18.32%. Slowly lower the temperature at a rate of 1°C / min to crystallize. Every time the temperature is lowered by 5°C, let the temperature rise by 0.5°C and then continue to cool down. When the temperature is lowered to -5°C, a large number of crystals are precipitated, and 96g of crystals are obtained by vacuum filtration. After low-temperature drying, the analytical purity of the crystals is 98.11. %, containing 1.88% of GA oligomers. After washing twice with acetone, 14.28 g of crystals were obtained, and the analytical purity was 99.34% after drying at low temperature.

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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...

Claims

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Application Information

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IPC IPC(8): C07C59/06C07C51/42
Inventor 赖崇伟李荣刘旋蒋贵仲
Owner SOUTHWEST RES & DESIGN INST OF CHEM IND
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