用氯仿萃取4-硝基吡啶的工艺条件研究

Extraction Technology of 4-Nitropyridine with Chloroform

合成并用氯仿作萃取溶剂来萃取分离4-硝基吡啶。考察了原料液酸碱度、萃取温度、萃取时间等因素对氯仿萃取4-硝基吡啶过程的影响,结果表明该萃取过程分配比随pH的升高而增大,在pH=9～10时分配比最大,再升高pH分配比又开始减小,萃取过程为一快速过程;水相中亚磷酸铵和氯化铵对萃取过程有盐析效应,使分配比增大;该萃取过程受温度影响不大,热效应为5.410kJ·mol-1。同时确定了pH=9～10时4-硝基吡啶在有机相与水相中分配平衡关系,当有机相和水相间体积比为3时,5级错流萃取的回收率为95%以上;当体积比为5时,7级逆流萃取4-硝基吡啶的回收率也可达96%以上。

4-Nitropyridine was synthesized, extracted and separated by using chloroform as extraction solvent. The influences of the pH of the solvent, extraction temperature and time of extraction etc. on the extraction process were investigated. The experimental results show that the extraction process is a fast extraction process The distribution ratio increases with the increase of pH of the aqueous solution and reaches its maximum when pH=9-10; then it decreases with further increase of pH. It was found that ammonium phosphite and ammonium chloride in the aqueous solution have the salting-out effect which can enhance the distribution ratio, and the extraction temperature has only a little effect on the extraction process. The distribution equilibrium relation of 4-nitropyridine with chloroform in aqueous and organic solution with pH=9-10 was determined, and the extraction enthalpy of 5.410 kJ·mol^-1 was obtained by experimental measurement. When the volume ratio of organic to aqueous phase is 3, the recovery yield of 5-stage cross-flow extraction is above 95%, and when the volume ratio reaches to 5, the recovery yield of 7-stage counter-flow extraction can be above 96%.