A kind of preparation method of methionine

Abstract

The invention provides an economic and high-efficiency methionine preparation method. The economic and high-efficiency methionine preparation method comprises the process of hydrolyzing of hydantoin intermediate, such as 5-(beta-methylthio-ethyl)hydantoin, and comprises the following specific steps of (1) mixing the hydantoin intermediate and a small amount of alkaline, sending into a reactor in phase I, and performing loop-open hydrolyzing reaction under the conditions of constant-power low-frequency ultrasonic wave and certain temperature; (2) continuously treating the liquid material in step (1) in a reactor in phase II, thoroughly hydrolyzing under the conditions of power same with the power in step (1) and higher-frequency ultrasonic wave and lower-temperature atmosphere, so as to obtain a saponification liquid of methionine; acidifying, so as to obtain the methionine. The economic and high-efficiency methionine preparation method has the advantages that the hydrolysis reaction efficiency of the hydantoin intermediate in the preparation process of the methionine is improved, and the reaction time is shortened by one time; the reaction temperature is greatly reduced, the hydrolysis yield rate is increased while the generation of side effect is reduced, and the requirement on the material of the reactor is lower.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for preparing methionine. Background technique [0002] D, L-methionine is an essential amino acid required by the human body, and it is also added to animal feed as an important functional nutrient. As the first limiting amino acid in animals, methionine cannot be synthesized in animals and needs to be ingested from food. At present, D, L-methionine mainly relies on chemical synthesis, and 5-(β- Methylthioethyl) hydantoin (hereinafter referred to as hydantoin intermediate) is obtained by alkaline hydrolysis and acidification. [0003] At present, most D, L-methionine production enterprises adopt the above-mentioned hydantoin synthesis method, and its main hydantoin intermediate is a five-membered heterocyclic ring structure with good stability. Therefore, it is necessary to use a large amount of alkali to participate in the reaction under high t...

AI Technical Summary

Problems solved by technology

[0006] No matter what alkali is selected for hydrolysis, the dosage is more than 1.6-2.0 hydantoin equivalents, the alkali consumption is large, the by-product salt or mother liquor with salt is high, and it is unfavorable for treatment

[0007] 1. The reaction temperature is 170-200°C, and the reaction pressure is 0.5-1.8MPa. The higher temperature will increase the reaction rate and cause some side reactions, and the product methionine may decompose to a certain extent at high temperature, resulting in malodorous gas

[0008] 2. The reaction time is about 15 to 40 minutes. The residence time is longer under high temperature reaction, which will further increase the hydrolysis by-products, cyclic pigment impurities and methionine decomposition products, resulting in the decrease of yield and the accumulation of impurities.

[0009] 3. In order to improve the hydrolysis efficiency, the existing technology mostly uses zirconium materials that can catalyze hydrolysis, and the investment in equipment is high.