Malononitrile purification method

Abstract

The invention relates to the technical field of compound purification, and particularly discloses a malononitrile purification method. The purification method of malononitrile specifically comprises the step of separating malononitrile from a malononitrile crude product through adoption of a melt crystallization method. According to the malononitrile purification method provided by the invention, a vacuum system does not need to be arranged, the required temperature is relatively low, the energy consumption is reduced by 50% or above, the refining cost and refining time of malononitrile are greatly reduced, and the finally obtained malononitrile pure product has extremely high purity and yield.

Description

technical field [0001] The invention relates to the technical field of compound purification, in particular to a method for purifying malononitrile. Background technique [0002] Malononitrile is an important pesticide and pharmaceutical intermediate. In terms of pesticides, malononitrile can be used to prepare 2-amino-4,6-dimethoxypyrimidine, and then used to produce sulfonylurea herbicides such as bensulfuron-methyl, pyrazosulfuron-methyl, etc., and bispyribac Class herbicides. In terms of medicine, malononitrile can be used to synthesize a series of important drugs such as vitamin B1, aminopterin, and triamterene. At the same time, malononitrile can also be used as an extraction agent for gold. [0003] At present, the purification process of the malononitrile crude product synthesized by cyanoacetamide is usually carried out by atmospheric pressure precipitation and then vacuum distillation. However, in actual operation, the solvent and malononitrile cannot be comple...

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Problems solved by technology

This will inevitably cause the solvent to be discharged through the exhaust port of the vacuum pump, resulting in organic gas pollution and waste of solvent.

At the same time, due to the high boiling point of malononitrile, even in the case of high vacuum, the initial temperature of the extracted malononitrile fraction is above 100°C, which consumes a lot of energy for steam.

And because the melting point of malononitrile is only 32-34°C, during the high vacuum vacuum distillation process, malononitrile gas will inevitably be sucked into the vacuum pump, causing blockage of the vacuum pump, which needs to be cleaned regularly

In addition, since the malononitrile crude product contains unreacted cyanoacetamide and high-boiling substances, the rectification method can generally only achieve about 99.5%. If you want to achieve a high purity of more than 99.9%, you need to carry out Re-distillation or increase the reflux ratio during rectification

In this way, the time of malononitrile at high temperature will be prolonged, which will inevitably cause the polymerization of part of malononitrile, seriously affecting the yield

[0004] Some downstream products of malononitrile, such as pyrimidinamine, have higher requirements on the content of malononitrile, and a small amount of impurities in malononitrile will also seriously affect the quality and efficacy of the final synthesized pyrimidinamine