摘要：
For the polymers of N-vinylpyrrolidone used in food and pharmaceutical fields,a purity of the N-vinylpyrrolidone monomer higher than 99.9% is required.However,it is often very difficult to meet the requirement by fractional distillation.To solve this problem,a crystallization process was applied to purify N-vinylpyrrolidone from industrial grade (99.5%) to pharmaceutical grade (99.9%).The effects of crystal seed addition amount,temperature of adding crystal seed,cooling rate,final crystallization temperature,crystallization time,heating rate,final sweating temperature,and sweating time on the purity and yield of the product were investigated.The appropriate operating conditions were obtained as follows: crystal seed addition amount is of 0.1% based on the weight of raw material,temperature of adding crystal seed of 11°C,cooling rate of 6°C/h,final crystallization temperature of 6°C,crystallization time of 20 min,heating rate of 6~8°C/h,final sweating temperature of 12°C,and sweating time of 30min.N-vinylpyrrolidone of industrial grade(99.5%)can be purified through single-stage crystallization to a purity more than 99.95% with a yield more than 74.5%.Compared to other separation methods,this method has obvious advantages.%对于应用于食品和医药等领域的N-乙烯基吡咯烷酮聚合物,要求N-乙烯基吡咯烷酮单体的纯度高于99.9%,但精馏法往往达不到要求.为了解决这个问题,本文采用结晶法对纯度为99.5%的工业级N-乙烯基吡咯烷酮进行提纯以制备纯度高于99.9%的医药级产品.考察了晶种添加量、晶种添加温度、降温速率、结晶终温、养晶时间、升温速率、发汗终温和发汗时间对最终产品的收率和纯度的影响,并确定了较为适宜的工艺条件:晶种添加量为原料质量的0.1%,晶种添加温度为11°C,降温速率为6°C/h,结晶终温为6°C,养晶时间为20min,升温速率为6~8°C/h,发汗终温为12°C,发汗时间为30min.在这些条件下通过单级结晶就可以将纯度为99.5%的N-乙烯基吡咯烷酮原料提纯至99.95%以上,收率大于74.5%.该方法相对其他分离方法具有较为明显的优势.
