Dimethyl malonate preparation method

Abstract

The invention discloses a dimethyl malonate preparation method. The shortcomings of mass decomposition of cyanoacetic acid and low yield caused by the traditional distillation concentration desalination are avoided by introducing hydrogen chloride into cyanoacetic acid reaction liquid to separate out sodium chloride; meanwhile, malonic acid and ammonium chloride are obtained by hydrolysis in a closed system, and hydrogen chloride gas is introduced to separate out ammonium chloride; after desalination, an esterification reaction can reduce the catalyst dosage and wastewater generation while a byproduct ammonium chloride is obtained. The method disclosed by the invention is simple to operate, low in production cost and high in product yield and generates a small quantity of three wastes, thereby being an environment-friendly and clean production method.

Description

technical field [0001] The invention relates to a method for preparing malonate, in particular to a method for preparing dimethyl malonate which is environmentally friendly and clean 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 chloroethyl ester, carbon monoxide and methanol as raw materials, gas-phase carbonylation under the action of a catalyst, and one-step synthesis of dimethyl malonate. The catalyst used is RhCl 3 (or CoCl 2 , PdCl 2 ) series and Co 2 (Co 8 ) series, although the yield of the catalytic carbonyl method is high, the process is complicated and the reaction conditions are harsh, so it is not suitable for in...

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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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