Preparation technical method of high purity 1, 1-dimethylurea

Abstract

The invention discloses a preparation method of high purity 1, 1-dimethylurea. 1, 1-dimethylurea is a medical and pesticide intermediate and an important synthesis raw material of rocket fuel 1, 1-dimethylhydrazine which is used in national defense chemistry. According to the preparation method, a hydrazine type remover and a reaction controlling are added to avoid problems in the prior art that influences are caused by hydrazine type compound impurities, and generation of by-products is caused because of the instability of the reactants, a certain amount of a weak alkali oxidizing agent is added, and then routine cooling crystallization, centrifugation, recrystallization, and vacuum drying are carried out so as to obtain the high purify intermediate 1, 1-dimethylurea crystalline powder contains no high toxicity residue, all impurity sources are controlled and eliminated, commercial large scale product is realized, cost is reduced, and equipment is simple.

Description

technical field [0001] The invention relates to the field of organic synthesis, in particular to an improved method for preparing 1,1-dimethylurea. Background technique [0002] 1,1-dimethyl urea can be used in the production of pesticides, medicines and national defense chemical industries, and it is also an important raw material for the synthesis of rocket dye 1,1-dimethylhydrazine, which is the method disclosed in US Patent No4046812. As 1,1-dimethylurea is widely used in different fields, more and more attention is paid to it, and its quality requirements are also getting higher and higher, and high-purity products with less impurities are becoming more and more popular. [0003] It is known that there are multiple methods for preparing 1,1-dimethylurea, which usually include: sodium cyanate and dimethylamine aqueous solution, reaction, concentration under reduced pressure, crystallization by cooling, centrifugal separation and vacuum drying to obtain the corresponding ...

AI Technical Summary

Problems solved by technology

The synthetic raw material of 1,1-dimethylurea, dimethylamine, is obtained through the reaction of methanol and ammonia at high temperature and high pressure, and the obtained mixture of monomethylamine, dimethylamine, trimethylamine and unreacted ammonia is obtained by distillation. Aqueous solution products, when the industrial dimethylamine aqueous solution prepared directly reacts with sodium cyanate, a series of ammonia derivatives contained in the first aspect dimethylamine aqueous solution also include complex impurity components such as hydrazines and hydrazones in the reaction Instability in the medium, leading to the formation of derivatives including highly toxic cyanide impurities directly affect the purity of 1,1-dimethylurea products, these toxic impurities and the obtained water-soluble 1,1-dimethylurea Physicochemical The properties are basically similar, and it is not easy to use simple purification steps to separate and purify, so the production cost is increased, and more importantly, the yield and the environment are directly affected