Dimethyl malonate preparation method

Abstract

The invention discloses an environment-friendly and clean dimethyl malonate preparation method. Hydrogen chloride gas is introduced into the mixed liquid of cyanoacetic acid and sodium chloride, and then methanol and sulfuric acid are added for an esterification reaction to obtain dimethyl malonate. The shortcomings of mass decomposition of cyanoacetic acid and low yield caused by the traditional distillation concentration desalination are avoided; meanwhile, after desalination, the esterification reaction can reduce the dosage of sulfuric acid and wastewater generation. The method is simple to operate, low in production cost, high in product yield and suitable for large-scale industrial production.

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 widely used in the fields of medicine, pesticides and dyes, and is an important raw material for the synthesis of pipemidic acid and repaglinide. At present, there are many production methods at home and abroad, most of which are catalytic carbonylation methods abroad, that is, using ethyl chloride, carbon monoxide and methanol as raw materials, and gas-phase carbonylation under the action of a catalyst to synthesize dimethyl malonate in one step. The catalyst used is RhCl 3 (or CoCl 2 , PdCl 2 ) series and Co 2 (Co 8 ) series, although the catalytic carbonyl method has a high yield, but the process is complicated and the reaction conditions are harsh, so it is not suitable for industrial...

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Problems solved by technology

[0008] The shortcoming that above-mentioned two kinds of methods exist 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 is concentrated and carries out esterification reaction, but cyanoacetic acid is easy to decompose in the late stage after being concentrated, and because reaction mixture There is a large amount of sodium chloride in it, and sulfuric acid reacts with sodium chloride during esterification, consuming a large amount of sulfuric acid and producing a large amount of acidic wastewater

The disadvantage of this method is similar to that of method 1, that is, because there are a large amount of inorganic salts in the later stage of concentrated distilled water, the stirring and heat transfer effects are poor, and it is easy to cause a large amount of cyanoacetic acid to decompose due to local overheating

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