Purification of carbazole by solvent crystallization under two forced cooling modes

To identify the effect of solvents and anthracene on the purification of carbazole, the solvent crystallization of carbazole was investigated with xylene, chlorobenzene and tetrachloroethylene (TCE) as solvents under two forced circulation cooling (FCC) modes. The co-crystalline experimental data were obtained from runs carried out at different anthracene levels between 1% (mass) and 10% (mass). The results showed that a uniform flake carbazole crystal obtained when using xylene and chlorobenzene under the FCC-1 mode with gradual cooling rate. Nevertheless, fine flake crystals grown under shock cooling of FCC-2 mode. It is beneficial to improving the purity of carbazole with chlorobenzene as solvent under cooling mode of FCC-1. Anthracene could promote the growth of carbazole in solution, and it has a significant influence on the purification of carbazole.