Preparation process of glycine

Abstract

The invention discloses a preparation process of glycine, which comprises amination, alkaline hydrolysis, ammonia discharge acidification, decolorizing, concentration, desalting, crystallization and recrystallization steps, wherein in the amination step, hydroxyacetonitrile and ammonia water are mixed in a tubular reactor, and a reaction is undergone at the temperature of 50-100 DEG C under the pressure of 0.5-2.0 MPa for 4-10 minutes; and in the alkaline hydrolysis step, 30-50 percent of sodium hydroxide solution is added into an alkaline hydrolysis reactor in advance, an amination liquid is collected from an amination liquid outlet, a reaction is undergone at the temperature of 60-90 DEG C under the pressure of between -0.01 MPa and -0.09 MPa, and ammonia in a system is recovered simultaneously. In the process, the tubular reactor is taken as an amination reactor, so that the reaction temperature and pressure are raised, the reaction time is shortened, and raw material decomposition, pyrolytic polymerization of aminoacetonitrile and the generation of byproducts are reduced; alkaline hydrolysis is performed during the collection of the amination liquid, the concentration of an alkaline liquor and the alkaline hydrolysis temperature are raised simultaneously, and ammonia in the system is recovered under reduced pressure, so that the alkaline hydrolysis reaction is more complete, the speed is higher, and the generation of colored impurities is reduced; and a mother liquor circular utilizing mode is established, so that the treatment amount of waste mother liquor is reduced, the product yield is increased, and the production cost is reduced.

Description

technical field [0001] The invention relates to the field of chemical industry, in particular to a technique for preparing glycine with hydroxyacetonitrile and ammonia water as raw materials. Background technique [0002] Glycine is an important fine chemical product, which is widely used in medicine, food, chemical industry, pesticide and other fields. There are many preparation techniques for glycine. Chinese patent CN1962611B discloses a technique for preparing glycine by the hydroxyacetonitrile method, which includes the following steps: 1) mixing hydroxyacetonitrile and ammonia water, and the molar ratio of the reaction liquid is hydroxyacetonitrile:ammonia=1: 2~10, control the reaction temperature between 20~60°C, and the reaction time is 0.5~8 hours to obtain the ammonia solution of aminoacetonitrile; 2) Add inorganic alkali directly to the ammoniated solution obtained in step 1), and the reaction material The molar ratio is aminoacetonitrile:inorganic base=1:0.7~3.0...

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Problems solved by technology

The above-mentioned preparation process has mild reaction conditions, easy control, and simple post-treatment, but it has the following problems: the reaction time in step 1) is long (≥0.5 hours), which easily leads to decomposition of raw materials, pyrolysis polymerization of aminoacetonitrile and formation of by-products; The concentration of inorganic alkali sodium hydroxide solution in step 2) is low (32%), the alkaline hydrolysis temperature is low (40~60°C), and the alkaline hydrolysis rate is slow, which will easily lead to the formation of colored impurities, thereby increasing the difficulty of decolorization and decolorization agent In addition, the volume of the alkaline hydrolysis solution is large, which also prolongs the subsequent concentration time and increases energy consumption; step 4) does not disclose the recycling method of the mother liquor, the waste mother liquor has a large amount of treatment, the product yield is low, and the production cost is high. high

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