Method for increasing yield of dimethyl malonate

Abstract

The invention provides a method for increasing the yield of dimethyl malonate. The method includes the steps of: 1) acidification reaction: adding acid or hydrogen chloride gas into sodium cyanoacetate to carry out reaction to obtain a cyanoacetic acid aqueous solution; 2) distillation and concentration: adding methyl cyanoacetate into the cyanoacetic acid aqueous solution, conducting distillation and concentration until no water flows out, and removing inorganic salt solid; 3) first esterification reaction: adding methanol and a catalyst into the desalted solution of step 2) to carry out esterification reaction, thus obtaining a solution containing methyl cyanoacetate; 4) desalting: removing inorganic salt solid from the solution; and 5) second esterification reaction: dividing a part of the desalted solution in step 3) and reusing it to step 2), adding methanol to the other part of solution, and carrying out esterification reaction under an acidic condition, thus obtaining dimethyl malonate. The method provided by the invention reduces the consumption of sulfuric acid and generation of wastewater, avoids the decomposition of cyanoacetic acid in the process of concentration and dehydration, and effectively improves the yield of dimethyl malonate.

Description

technical field [0001] The invention relates to the field of chemical industry, in particular to a method for improving the yield of dimethyl malonate. 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 are as follows: [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 reaction after being concentrated, but cyanoacetic acid is easily decom...

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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

This method still has the phenomenon of decomposition of cyanoacetic acid due to local uneven heating in the process of secondary concentration and desalination

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