Clean process for continuously synthesizing glycine

Abstract

The invention discloses a clean process for continuously synthesizing glycine. The process comprises the following steps: preheating a carbon dioxide ammonia water solution prepared from an ammonia source, a carbon source and water, mixing the preheated solution with glycolonitrile, performing continuous synthesis, reduced pressure flash evaporation, continuous hydrolysis, gas stripping, concentrating, cooling and crystallizing, centrifuging for the first time, carrying out hot-melting recrystallization, centrifuging for the second time and drying to obtain a glycine product. Part of carbon dioxide generated by hydrolysis in the hydrolysis reaction process is continuously separated; and a carbon dioxide and ammonia recovery system sequentially absorbs the gas phase obtained by gas stripping, hydrolysis separation and reduced pressure flash separation to obtain a carbon dioxide ammonia water solution, and the carbon dioxide ammonia water solution is recycled to the reaction system. According to the process, the yield of glycine is increased by restraining iminodiacetonitrile side reaction; through timely release of each gas phase in the system and reasonable arrangement of the recovery sequence, the difficulty of recycling carbon dioxide and ammonia in the system is reduced, the loss of carbon dioxide and ammonia is reduced, the hydrolysis one-way conversion rate is improved, the hydrolysis time is greatly shortened, and the process is an environment-friendly and clean process for producing glycine.

Description

technical field [0001] The invention relates to a clean process method for continuously synthesizing glycine by using hydroxyacetonitrile as a raw material through a hydantoin process, belonging to the field of fine chemical intermediates. Background technique [0002] Glycine, also known as aminoacetic acid, English Glycine, chemical formula C2H5NO2, molecular weight 75.07, is the simplest amino acid structure, as an important fine chemical intermediate, widely used in pesticides, medicine, food, feed, daily chemical and organic synthesis and other fields. my country is the largest producer and consumer of glycine in the world, and the market size of glycine exceeds 350,000 tons. [0003] The conventional production process of glycine in my country is the ammonolysis of chloroacetic acid. However, with the strengthening of environmental awareness in recent years, the environmental problems brought about by the ammonolysis of chloroacetic acid have become increasingly promi...

AI Technical Summary

Problems solved by technology

However, the excess ammonia and carbon dioxide in the system and the ammonia and carbon dioxide released by hydrolysis are all recovered after the completion of the two-stage reaction, which increases the difficulty of recycling ammonia and carbon dioxide, and is not conducive to the progress of the hydrolysis reaction, and the single-pass yield of hydrolysis is low ; In the proportioning of raw materials, the amount of ammonia is greater than the amount of carbon dioxide, so that the side reaction of ammoniating hydroxyacetonitrile to generate iminodiacetonitrile is more obvious, which affects the yield and purity of product glycine

Chinese patents CN201710969775 .3 and CN201910370199 .X both propose the use of tank-type series reactors to realize the hydrolysis of hydantoin, which also has the problems of long hydrolysis time, low yield per pass of hydrolysis, difficult recovery of ammonia and carbon dioxide, and side reactions of iminodiacetonitrile formation Weaknesses not well contained

Although the microchannel reactor can realize the continuous synthesis of glycine well, because the synthesis and hydrolysis of hydantoin are not fast reactions, the advantages of the microchannel reactor cannot be fully utilized, and its production capacity is small and its corrosion resistance is poor. The disadvantages of this method make it difficult to scale up and operate stably; the ammonia and carbon dioxide in the system are recovered by gas stripping after the hydrolysis reaction is completed, which is difficult to apply mechanically; the single-pass yield of hydrolysis is also low; well contained

[0011] Chinese patent CN101148417 proposes to use a system composed of tubular reactors and multi-stage tower bed reactors in series to realize the continuous production of glycine, which returns the mainly carbon dioxide-containing gas that is separated from the pressure relief during the reaction and the reaction process directly to the cycle. Although the separate recycling of carbon dioxide and ammonia in the system can be realized to a certain extent, because the carbon dioxide separated by pressure release still contains a certain amount of ammonia, it needs to be pressurized by a compressor when it is directly returned to the system, and there is ammonium carbonate formed during the pressurization process. or the problem of ammonium bicarbonate blocking the compressor; it also has the problems that the hydrolysis time is too long, the hydrolysis single-pass yield is low and the side reaction of iminodiacetonitrile is not well contained

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