Method for preparing high-purity polymerization-grade crystallized lactic acid

Abstract

The invention relates to a method for preparing high-purity polymerization-grade crystallized lactic acid. The method comprises the steps as follows: performing filtration, acidolysis, activated carbon decoloration, ion exchange resin treatment, vacuum concentration and short-range distillation refinement on an L-lactic acid fermentation broth to obtain a polymerization-grade lactic acid liquid with the purity being 90%-95% (by weight); sending the polymerization-grade lactic acid liquid into a vacuum evaporative crystallizer for evaporative crystallization at the vacuum degree of -98 Kpa andtemperature of 15-25 DEG C; when the graining point is reached, adding L-lactic acid seed crystals for graining, precisely controlling the supersaturation coefficient at 1.10-1.15 until finishing crystallization after graining; performing centrifugal separation and drying tretament on crystallized lactic acid crystals to obtain a crystallized L-lactic acid product. The polymerization-grade lacticacid liquid with the purity being 90% or above is used as the raw material, lactic acid is crystallized through ultralow-temperature evaporative crystallization at 15-25 DEG C, the L-lactic acid crystals with the purity being 99% or above are obtained, the lactic acid preparation process is optimized, and the product quality is improved.

Description

technical field [0001] The invention belongs to the technical field of chemical production, and relates to a method for preparing high-purity polymer-grade crystalline lactic acid. Background technique [0002] L-lactic acid is widely used in various fields such as food, medicine, daily chemical and industry. In recent years, with the continuous shortage of petrochemical resources, the production of many chemically synthesized polymer materials has been restricted. L-lactic acid based on biomass resources is therefore widely used to process and produce environmentally friendly biodegradable materials such as poly-L-lactic acid. With the increasing demand of L-lactic acid, how to produce L-lactic acid efficiently and at low cost is particularly important. As a raw material for the production of polylactic acid, the higher the purity of L-lactic acid, the better the performance of polylactic acid products can be obtained, so the higher the purity of L-lactic acid, the higher...

AI Technical Summary

Problems solved by technology

Although the final step of the process route is short-path distillation and refining, although some organic impurities with different boiling points can be separated and removed, a high separation effect cannot be achieved. Many of the impurities are close to the boiling point of lactic acid, so it is difficult to effectively separate and obtain high-quality L with a purity higher than 95%. - lactic acid

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