Method and device for using crude hydrocyanic acid to continuously produce D, L-methionine

Abstract

The invention relates to a method and device for using crude hydrocyanic acid to continuously produce D, L-methionine. The device comprises a hydrocyanic acid synthetic tower, an acid tower, a multi-level series tank reactor, a static mixing reactor I, a stripping tower I, a static mixing reactor II, a tank reactor, a stripping tower II and a neutralizing kettle. The method for continuously producing the D, L-methionine comprises the steps of the preparation of cyanic acid mixed gas II, the preparation of 2-hydroxy-4-methylthio-butyronitrile in the multi-level series tank reactor, the preparation of 2-amino-4-methylthio-butyronitrile in the static mixing reactor I, the preparation of D, L-methionine potassium in the static mixing reactor II and the tank reactor, the preparation of the D, L-methionine through the neutralization in the neutralizing kettle, and the treatment on products or reaction residues by using a low-temperature storage tank, an incinerator, a stripping tower, a washing kettle and the like. According to the device and method, provided by the invention, crude hydrocyanic acid and crude methylthiopropanal are used for continuously producing the D, L-methionine, the production cost is low, the side reactions are few, the yield is high, and industrial large-scale continuous production can be realized.

Description

Technical field [0001] The invention relates to the field of fine chemicals, in particular to a method and a device for continuously producing D,L-methionine by using a mixed gas of hydrocyanic acid. Background technique [0002] D,L-methionine, also known as methionine, is one of the basic units of protein. It is the only amino acid that contains sulfur among essential amino acids. Its structural formula is as follows: [0003] [0004] D,L-methionine is not only involved in the transfer of methyl groups in animals, the metabolism of phosphorus and the synthesis of adrenaline, choline, and creatine, but also the raw material for the synthesis of protein and cystine, so it is widely used in medicine, food, and feed. And cosmetics and other fields, which are used as feed additives in a large amount. However, due to the limitations of technology and production costs, domestic production cannot meet the demand, and a large amount of imports from abroad are required. [0005] D,L-methi...

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Problems solved by technology

[0006] Although many patents have been applied for the preparation of D,L-methionine by the Hyne method at home and abroad, these patents mainly focus on two aspects. The first aspect is the synthesis of 3-methylthiopropionaldehyde, cyanide, carbon dioxide and ammonia Three-component reaction in aqueous solution, as reported in patents CN102633699A and US5663409, although the process is simple to operate, it is easy to cause side reactions such as degradation and polymerization of organic raw materials, resulting in more hydantoin by-products, resulting in D,L-methyl sulfide The yield of amino acid salt declines, and in this three-component reaction, in order to reduce the generation of by-product as much as possible, 3-methylthiopropionaldehyde and hydrocyanic acid require rectification and purification, which will inevitably lead to D,L-methionine The production cost of acid salt increases; secondly, 2-hydroxyl-4-methylthiobutyronitrile reacts with the aqueous solution of ammonium bicarbonate in two components, although this process greatly reduces the degradation of organic raw materials, side reactions such as polymerization and operation Simple, but in order to minimize the formation of by-products, 3-methylthiopropionaldehyde and hydrocyanic acid require rectification and purification, which will inevitably lead to an increase in the production cost of D,L-methionine salt

[0007] Patent CN1103066A discloses another method for producing D, L-methionine and its sodium salt solution, that is, the reaction of 3-methylthiopropionaldehyde with hydrocyanic acid to obtain 2-hydroxyl-4-methylthiobutyronitrile, and then React with ammonia to obtain 2-amino-4-methylthiobutyronitrile, and 2-amino-4-methylthiobutyronitrile undergoes hydrolysis reaction with sodium hydroxide to obtain D,L-methionine sodium aqueous solution, or neutralize with acid , to obtain D, L-methionine. This method creates another production method for preparing D, L-methionine, which greatly simplifies the operation, improves the yield, and reduces the production cost. However, in order to obtain D, L-methionine, And produce a large amount of low-value sodium sulfate or sodium chloride, and a large amount of waste water

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