A method for refining and purifying caprolactam

Abstract

The invention discloses a method for refining and purifying caprolactam. Through crystallizing low-water-content crude caprolactam at a constant temperature, one part of caprolactam with high qualityis obtained, through crystallizing room-temperature-crystallization high-water-content mother liquor at a low temperature and then performing distillation, the other part of caprolactam with high quality is obtained, wherein the low-temperature-crystallization mother liquor is evaporated to obtain circulation materials which participate in constant-temperature crystallization. A constant-temperature and low-temperature combined crystallization way is adopted and is matched with distillation and evaporation processes to realize the efficient refining and purification of the caprolactam. The constant-temperature and low-temperature crystallization has the advantages of low energy consumption, small effluent discharge, lowered production cost and improved safety. The method has the advantagesof high product yield, short technical process and low equipment investment. No inorganic solvent is used, the process is simple, and production cost is greatly lowered. The obtained caprolactam hasgood quality, each index is superior to the standard of a national standard premium grade; three waste (waste gas, waste water, industrial residue) discharge amount is small, and environment pollutionis low.

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 is very useful. widely. In the prior art, most manufacturers adopt the production route of converting cyclohexanone into cyclohexanone oxime, and then converting it into caprolactam through rearrangement. Due to the long route, the reaction is more complicated, accompanied by the occurrence of many side reactions, resulting in the presence of Various impurities. The fiber manufacturing industry has very high requirements on the purity of caprolactam, so it is necessary to remove as many impurities...

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Problems solved by technology

Although this refining process can obtain high-purity caprolactam products, there are also problems such as long process, large investment, complicated process control, difficulty in ensuring stable product quality, high energy consumption, and large discharge of ion exchange waste liquid, resulting in high pressure on environmental protection. The relatively obvious shortcomings such as high safety risks in the hydrogen process, especially in order to avoid the loss of caprolactam in this refining process, the three-effect evaporation condensate rich in low-boiling light impurities is returned to the front unit due to a certain amount of caprolactam, and re-enters the system, and the distillation raffinate rich in high-boiling heavy impurities is also returned to the neutralization unit and re-enters the system. This traditional refining process, which sacrifices quality to ensure yield, advocates "high efficiency, high quality, low consumption, and environmental protection" today. Under the current situation, there is an urgent need for appropriate improvements and enhancements

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