Purification of p-Cresol, o-Cresol, m-Cresol, and 2,6-Xylenol from the Quaternary Mixture by Three-Phase Crystallization

Three-phase crystallization (TPC) was applied in this work to purify the major component from quaternary liquid mixtures consisting of p-cresol, o-cresol, m-cresol, and 2,6-xylenol. As TPC is operated in a series of three-phase transformations by decreasing temperature and reducing pressure, TPC combines melt crystallization and vaporization to produce the major component crystalline product along with the vapor mixture from the liquid mixture. A model based on the van't Hoff equation and Raoult's law coupled with mass and energy balances was proposed to determine a series of three-phase transformation conditions, which were adopted to direct the batch TPC experiments. The experimental purity and recovery ratio of the final product for purification of p-cresol, o-cresol, m-cresol, or 2,6-xylenol were compared with the calculated results predicted by the model. The order of difficulty for purification among p-cresol, o-cresol, m-cresol, and 2,6-xylenol was examined.