A kind of separation and purification method of methionine

Abstract

The invention discloses a separation and purification method of methionine. The separation and purification method includes the steps of firstly, adding acid into methionine salt for acidification, cooling, crystalizing, performing suction filtration to obtain filtrate and methionine crystals, and further washing the methionine crystals to obtain washing liquor and wet methionine; secondly, combining the filtrate and washing liquor obtained in the first step to obtain mixed liquid, concentrating the mixed liquid to obtain mother liquor with salt content being 10-28wt% and methionine content being 2-5%, decoloring the mother liquor, filtering with a precision filter, performing homogeneous membrane electrodialysis, and desalting until salt in a light chamber is lowered to 3-7wt%; thirdly, performing heterogeneous membrane electrodialysis on the solution in the light chamber after the treatment of the second step so as to perform deep desalting until the salt in the light chamber is lowered to below 0.1wt% to obtain a methionine aqueous solution, and further concentrating and crystalizing the methionine aqueous solution to obtain the methionine. The method has the advantages that the salt liquid containing the methionine needs not to be diluted, inorganic salt filtrate containing the methionine needs not to be concentrated repeatedly, and the methionine can be prevented from having thermal decomposition caused by the repeated concentration to generate malodorous gas.

Description

technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a method for separating and purifying methionine. Background technique [0002] D, L-methionine, also known as methionine, is one of the basic units of protein and the only amino acid containing sulfur among the essential amino acids. In addition to participating in the transfer of methyl groups in animals, the metabolism of phosphorus and adrenaline, choline, In addition to the synthesis of creatine, it is also a raw material for the synthesis of protein and cystine. [0003] Methionine is widely used in the fields of medicine, food, feed and cosmetics, among which it is used in a large amount as a feed additive. The global demand for methionine has reached 1.8 million tons per year, and China's demand for methionine in 2015 exceeded 160,000 tons , and at present, in addition to the 100,000 tons of methionine produced by Ningxia Ziguang Tianhua Methionine Co., Ltd., ...

AI Technical Summary

Problems solved by technology

[0005] Therefore, for the use of sodium hydroxide to hydrolyze hydantoin, the hydrolysis generates a saponified liquid containing sodium carbonate and sodium methionine. After the saponified liquid is deaminated and carbon dioxide, it is acidified by adding sulfuric acid to a pH of 5.0-5.5, and cooled to 40°C for crystallization. , separate methionine, wash with water, and dry to obtain methionine product; the washing water is combined with methionine-containing sodium sulfate mother liquor and then concentrated at high temperature, especially heated to about 100°C (at this time, the solubility of methionine is the largest and the solubility of sodium sulfate is low), and then Precipitate a large amount of sodium sulfate, centrifuge sodium sulfate while it is hot, cool the filtrate to 35°C-40°C, crystallize methionine, wash with water, and dry to obtain methionine product. The sodium sulfate filtrate containing methionine is repeatedly concentrated and cooled to obtain sodium sulfate and methionine respectively. , in order to avoid the loss of methionine, the mother liquor should not be discharged as much as possible, resulting in methionine being under high-temperature cooking for a long time, part of the methionine is thermally decomposed, and dimethyl disulfide or methyl mercaptan ( See figure 1 Shown; CN104693082A), these substances can remain in the sodium sulfate mother liquor and the cooling water of efflux, cause the sodium sulfate mother liquor that circulates for a long time to have stench, the bad smell of sodium sulfate workshop operation environment, influence surrounding environment, and also cause methionine Partially decomposed, the COD of the discharged mother liquor is high, it is difficult to carry out biochemical treatment, and the sodium sulfate mother liquor is continuously circulated, and a small amount of sodium formate, sodium acetate, and sodium propionate in the mother liquor will continue to accumulate. These substances lead to the quality of subsequent methionine products. The main reasons for the decline are: first, the decomposition of methionine and the polymerization of methionine, especially the formation of dimers of methionine, and the accumulation of organic impurities after the decomposition of methionine in the system, resulting in the unpleasant smell of crystallized methionine The second is that the sodium formate, sodium acetate, sodium propionate, 2-hydroxyl-4-methylthiobutyrate, etc. produced by the saponification solution accumulate in the system, thus affecting the quality of methionine products

The above factors have led to the biggest outstanding problem of methionine production processes such as Adisseo, Chongqing Ziguang Tianhua and Volga, which is environmental protection.

The best way to solve this problem is incineration, which inevitably consumes more energy, increases the loss of methionine and production costs

Patent CN104693082A discloses a method for separating and purifying methionine by continuous chromatography. This method uses continuous chromatography to treat sodium sulfate mother liquor containing methionine to achieve the purpose of desalination. However, there are two biggest problems: first, the investment in chromatography is large; The second is that the concentration of methionine and sodium sulfate obtained after chromatographic separation is diluted by two times, and the subsequent concentration and water removal consume more energy.

[0006] Although heterogeneous membrane electrodialysis can be used for desalination treatment, this desalination can only remove the feed liquid with low salt content, and there are strict requirements on the salt content in the feed liquid. If the salt content is too high, it will The problems of high desalination power consumption, low desalination rate and low methionine rejection rate of heterogeneous membrane electrodialysis

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