水及杂质积累对粗蒽溶剂结晶精制咔唑的影响

考察了粗蒽结晶分离过程在溶剂循环使用时二甲苯中杂质和乙醇中水的积累对精制咔唑的影响。结果表明，随着二甲苯循环次数的增加，原料中的主要杂质萘、菲和芴在回收二甲苯中逐渐积累，其中萘的浓度最高可达0.35 mg·ml^-1，滤饼中咔唑的含量降低2.77%（质量）左右，收率降低高达7.05%（质量）。同时，母液中杂质的积累使溶剂回收困难，二甲苯的损失率随着循环次数增加而增加，由单程实验的44.75%（体积）增加到循环3次时的79.17%（体积）。原料中的水分随着溶剂循环在回收溶剂中逐渐积累，循环使用3次后，乙醇的含水量高达6.65%（体积）。乙醇含水量在0～12%（体积）之间时，咔唑纯度在98%（质量）以上。含水量在0～6%（体积）时，咔唑的相对结晶度随含水量增加从45.67 %降到40.79 %；含水量为9%和12%时，相对结晶度分别为48.85% 和48.52%。

Effect of water and impurity accumulation in reclaimed solvent on crystallization of carbazole from crude anthracene

To investigate the effect of water and other impurities in solvents on crystallization of carbazole from crude anthracene, the accumulation amount of impurities in xylene and water in ethanol in the solvent recycling were studied. Results showed that with the increase of xylene recycling, the main impurities in mother solution gradually accumulated in xylene, with the concentration of naphthalene up to 0.35 mg·ml^-1 after recycling twice, and the carbazole content in the corresponding filter cake was reduced about 2.77% (mass) and the yield decreased 7.05% (mass). At the same time, the accumulation of impurities makes solvent recovery difficult, and the loss ratio of xylene increased from 44.75% (vol) to 79.17% (vol) after recycling three times. Water was gradually accumulated to 6.65% (vol) in ethanol. The purity of carbazole was higher than 98% (mass) when the water content added was between 0 to 12% (vol). The relative crystallinity of carbazole decreased from 45.67% to 40.79% when added water content is between 0 and 6% (vol) in ethanol; with the added water content of 9% (vol) and 12% (vol) in ethanol, it increased to 48.85% and 48.52%, respectively.