Improvement of separation and purification process for anthracene and carbazole from coal tar

A relatively advanced industrialized method used for separation and purification of anthracene and carbazole from coal tar is crystallization-distillation process.The impurities are mainly removed by the crystallization process.However,the separation and purification of crystallization process need to be further improved because of too many steps and relatively poor separation effect.In addition,the experimental results indicate that the retention of mother liquor with high content of impurities in crystals is the key factor that greatly influences the improvement of the separation of anthracene and carbazole from coal tar.Therefore,a new process of crystallization and filtration-distillation is proposed in this paper.In the new process,crystallizer is combined with gas-liquid separator to achieve the synchronization of crystallization and suction filtration,which can improve separation efficiency by reducing the retention of mother liquor in crystallization,and obtain the high purity and recovery rate of the product with a small amount of solvent circulation.This new process is promising and economical,with low energy consumption and large production capacity.