Method for using hydrocyanic acid mixed gas to prepare 2-hydroxy-4-methylthio-butyronitrile and continuous production method for 2-hydroxy-4-methylthio-butyronitrile

Abstract

The invention belongs to the field of chemical engineering, and relates to a method for using hydrocyanic acid mixed gas to prepare 2-hydroxy-4-methylthio-butyronitrile and a continuous production method for the 2-hydroxy-4-methylthio-butyronitrile. The method comprises the following steps: preparing hydrocyanic acid mixed gas I by using methane, ammonia gas and oxygen as raw materials and adopting the synthetic principle of an Andrussow method; deaminizing the hydrocyanic acid mixed gas I to obtain hydrocyanic acid mixed gas II; enabling the hydrocyanic acid mixed gas II to fully react with methylthiopropanal under the catalysis of alkali, so as to obtain the 2-hydroxy-4-methylthio-butyronitrile. According to the invention, the method adopts raw materials not purified, the raw materials are low in cost and easy to obtain, and the prepared 2-hydroxy-4-methylthio-butyronitrile is high in yield and high in purity; the obtained 2-hydroxy-4-methylthio-butyronitrile reaction system not subjected to purification and separation is stable in property, and can be stored for a long time and used for the production of down-stream products conveniently. The continuous production method for the 2-hydroxy-4-methylthio-butyronitrile particularly adopts a multi-level series tank reactor, so that the continuous production method can realize industrial large-scale continuous production, is low in production cost, efficient, environment-friendly and suitable for industrial popularization and application.

Description

technical field [0001] The invention aims at the field of chemical industry, and relates to a method for preparing 2-hydroxy-4-methylthiobutyronitrile by using hydrocyanic acid mixed gas and a continuous production method thereof. Background technique [0002] 2-Hydroxy-4-methylthiobutyronitrile (MMP-CN for short) is an important intermediate for the production of D,L-methionine or D,L-2-hydroxy-4-methylthiobutyric acid. As shown in the following formula: [0003] [0004] The yield size and cost input of 2-hydroxy-4-methylthiobutyronitrile affect the quality and quality of the final produced D,L-methionine or D,L-2-hydroxy-4-methylthiobutyric acid Cost plays an important role. [0005] In theory, the preparation of 2-hydroxy-4-methylthiobutyronitrile is known, mainly including the following two ways: [0006] (1) Methylthiopropionaldehyde is prepared by reacting with hydrocyanic acid under the catalysis of alkali; [0007] (2) Methylthiopropionaldehyde is prepared by...

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Problems solved by technology

[0010] Obviously, in these bibliographical reports, no matter which way is adopted to synthesize 2-hydroxyl-4-methylthiobutyronitrile, in order to obtain high yield, purer hydrocyanic acid is needed, and hydrocyanic acid is often excessive, hydrogen Additional distillation purification and excessive use of cyanic acid will result in an increase in costs, which, especially on an industrial scale, will lead to huge economic losses

Furthermore, as the method disclosed in US2745745, under the use of inappropriate catalyst, the formation of by-products in the cyanidation process may be caused, which will cause troubles for subsequent purification and downstream production

[0011] As far as the industrial production unit of 2-hydroxyl-4-methylthiobutyronitrile is concerned, if high-purity hydrocyanic acid liquid is used, not only the production cost of hydrocyanic acid is higher, but also the liquid hydrocyanic acid and 3-methylthio The reaction of propionaldehyde under the action of the catalyst will release a large amount of heat, which is not easy to control during the reaction process, and it is very dangerous. Continuous production is relatively difficult, and the requirements for equipment are relatively high.

Therefore, the production of 2-hydroxyl-4-methylthiobutyronitrile often adopts the gasification of hydrocyanic acid liquid and passes through the 3-methylthiopropionaldehyde containing catalyst, although this method has controlled the exothermic reaction and is easy to operation, but it is more difficult to achieve large-scale continuous production

Furthermore, the 3-methylthiopropanal reported in the patent is all refined, and the energy consumption of refined 3-methylthiopropanal is relatively large, and the 3-methylthiopropanal entrained by the light and heavy components is Incineration together, resulting in the loss of 3-methylthiopropanal

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