Environment-friendly clean method for preparing dimethyl malonate

Abstract

The invention discloses an environment-friendly clean method for preparing dimethyl malonate. The method comprises steps of neutral reaction, cyaniding reaction, acidizing reaction, steaming water desalination, esterification reaction and the like, wherein inorganic salt in a cyanoacetic acid aqueous solution is removed in the step of steaming water desalination, and the preferable technical scheme of steaming water desalination is carried out twice. The inorganic salt-sodium chloride mixed in cyanoacetic acid is removed through steaming water desalination before the esterification reaction, the reaction of sulfuric acid and sodium chloride are avoided in the esterification process, and the consumption of sulfuric acid and the waste water generating capacity are reduced, so that the method for preparing the dimethyl malonate is environment-friendly and clean. The steaming water desalination is carried out twice, so that the phenomenon that cyanoacetic acid is decomposed due to local overtemperature caused by large salt content in the later stage of one-time steaming concentration is avoided.

Description

technical field [0001] The invention relates to a method for preparing malonate, in particular to an environmentally friendly and clean method for preparing dimethyl malonate using chloroacetic acid and sodium cyanide as raw materials. Background technique [0002] Dimethyl malonate is an intermediate of medicines, pesticides and dyes. At present, there are many production methods at home and abroad. In China, cyanation esterification is mainly used, that is, chloroacetic acid, sodium cyanide and methanol are used as raw materials, and after neutralization , Cyanide, acidification and esterification processes to obtain dimethyl malonate. [0003] Common synthetic methods: [0004] 1. Direct esterification of cyanoacetic acid [0005] [0006] The shortcoming that this method exists is: the reaction process of synthesizing cyanoacetic acid produces a large amount of inorganic salt sodium chloride, and the mixture of cyanoacetic acid and salt carries out esterification re...

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Problems solved by technology

[0006] The shortcoming that this method exists is: the reaction process of synthesizing cyanoacetic acid produces a large amount of inorganic salt sodium chloride, and the mixture of cyanoacetic acid and salt carries out esterification reaction after being concentrated, but cyanoacetic acid is easy to decompose after being concentrated, and because there is A large amount of sodium chloride, sulfuric acid reacts with sodium chloride during esterification, consumes a large amount of sulfuric acid and produces a large amount of acidic wastewater

[0009] This method also has the same disadvantages as method 1

[0010] In addition, there are methods to report the use of calcium cyanoacetate instead of sodium cyanoacetate, but the above problems cannot be solved

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