N-vinyl pyrrolidone purification system and method

Abstract

The invention relates to an N-vinyl pyrrolidone purification system and method. The N-vinyl pyrrolidone purification system comprises a first rectification unit, a first crystallization system and a third rectification unit which are sequentially connected in series through pipelines, a second rectification unit and a second crystallization system which are connected in series,and an NVP storage tank, wherein the first rectification unit receives a synthesis reaction liquid containing NVP, carries out rectification treatment and outputs a first distillate and a first kettle distillate, the first crystallization system receives the first distillate, carries out crystallization purification and outputs a first crystallization liquid, the third rectification unit receives the first crystallization liquid, carries out rectification treatment and outputs a seventh distillate, the second rectification unit carries out rectification treatment on the first kettle distillate and then outputs a second distillate, the second kettle distillatereturns to the first rectification unit for rectification treatment, the second crystallization system crystallizes the second distillate to obtain a second crystallization liquid, and the NVP storage tank receives the seventh distillate and the second crystalline liquid. According to the invention, cascade rectification and gradient crystallization are coupled, NVP can be continuously refined, and the yield of NVP can be improved.

Description

technical field [0001] The invention belongs to the technical field of N-vinylpyrrolidone preparation, and in particular relates to an N-vinylpyrrolidone purification system and method. Background technique [0002] N-methylpyrrolidone (NVP) is a kind of fine chemicals with excellent performance, which puts forward high requirements on the purity of NVP. When adopting the acetylene synthesis method (Reppe method) to synthesize NVP, most of them use a strong base such as KOH as a catalyst to catalyze the vinylation reaction of a-pyrrolidone and acetylene. The defects of this method are very obvious, and there are many reaction steps. The five-step reaction of hydrogenation, catalytic dehydrogenation to form a ring, ammonolysis, and alkyne addition to obtain the monomer, the amount of non-volatile polymerization by-products generated during the synthesis reaction of the monomer is relatively large, so the post-treatment of the product is cumbersome, not only Cause target prod...

AI Technical Summary

Problems solved by technology

When adopting the acetylene synthesis method (Reppe method) to synthesize NVP, most of them use a strong base such as KOH as a catalyst to catalyze the vinylation reaction of a-pyrrolidone and acetylene. The defects of this method are very obvious, and there are many reaction steps. The five-step reaction of hydrogenation, catalytic dehydrogenation to form a ring, ammonolysis, and alkyne addition to obtain the monomer, the amount of non-volatile polymerization by-products generated during the synthesis reaction of the monomer is relatively large, so the post-treatment of the product is cumbersome, not only It leads to a decrease in the yield of the target product NVP, and complicates the separation and purification of NVP

[0003] At present, the separation and purification of NVP adopts semi-continuous separation. In the last step, batch distillation is required to produce NVP products with qualified purity. The residence time of this step is about 24-30 hours. Since N-vinylpyrrolidone is a heat-sensitive substance, the material is in the rectification The residence time in the tower is as high as 30-40 hours. Due to the high temperature in the rectification process, a large amount of N-vinylpyrrolidone is self-polymerized, thereby reducing the yield of the target product NVP. Not only the production efficiency of the enterprise is not high, but also The production cost of enterprises has risen. In addition, the by-products of self-polymerization have also brought certain environmental pollution problems.

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