Method for refining caprolactam by organic solvent crystallization

Abstract

The invention discloses a method for refining caprolactam by organic solvent crystallization. The method is concretely characterized in that solvent crystallization and recrystallization are used; a impurity-containing caprolactam water solution is subjected to benzene extraction to obtain a caprolactam solution; the caprolactam solution is subjected to evaporative crystallization and recrystallization to obtain high-quality caprolactam; benzene is refined to be cyclically used. The solvent crystallization and recrystallization are used for realizing impurity-containing caprolactam refining and purification; the process energy consumption is low; the product yield is high; the technological process is short; the equipment investment is low; the product quality is good; various items of indexes such as the chromaticity, the acidity and alkalinity, the volatile alkali content, the ultraviolet absorption value and potassium permanganate oxidation value of the finished product can stably reach national standard premium grade requirements; meanwhile, the discharge of three wastes (waste water, waste gas and waste solid) is little; the environment pollution is little.

Description

technical field [0001] The invention relates to a method for refining and purifying organic matter, in particular to a method for refining and purifying caprolactam. Background technique [0002] Caprolactam is an important organic chemical raw material. It is mainly used as a raw material for the production of polyamide 6 engineering plastics and polyamide 6 fibers. It can also be used for the production of antiplatelet drugs such as 6-aminocaproic acid and laurocaprolactone. It has a wide range of uses. At the same time, limited to the characteristics of its downstream products, the quality requirements for caprolactam as a raw material are relatively high. At present, the mainstream caprolactam production process in the industry is cyclohexanone oximation followed by rearrangement, followed by separation and purification to obtain qualified products. [0003] At present, the crude caprolactam refining method adopted by various manufacturers is to produce finished caprola...

AI Technical Summary

Problems solved by technology

Although the above-mentioned traditional refining process can obtain high-purity caprolactam products, there are long processes, large investment, complicated process control, difficulty in ensuring stable product quality, high energy consumption, and large discharge of ion exchange waste liquid, resulting in great pressure on environmental protection. , high safety risks in the hydrogenation process and other obvious shortcomings, especially in order to avoid the loss of caprolactam in the refining process, the condensate of three-effect evaporation, flash evaporation and pre-distillation rich in low-boiling light impurities and azeotropic impurities with water Because it contains a certain amount of caprolactam and needs to be recovered, it is returned to the previous neutralization and crystallization process, and then recirculated into the crude product refining system. At the same time, the distillation raffinate rich in high-boiling heavy impurities also needs to be recovered because it contains a certain amount of caprolactam. After being returned to the previous neutralization and crystallization process, it is also recirculated into the crude product refining system. This traditional refining process that sacrifices quality to ensure yield is under the current situation of advocating "high efficiency, high quality, low consumption, and environmental protection". , there is an urgent need for appropriate improvements and enhancements

Images