(31g) A New Separation Technique – Distillative Crystallization

Distillative crystallization (DC) is a new separation technique which combines distillation and crystallization to separate the mixtures with the close boiling temperatures. Basically, DC is operated at a triple-point condition, in which the liquid is simultaneously vaporized and crystallized due to the three-phase equilibrium. In essence, the process is continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. Thus, crystal washing is not required since only pure solid crystals remain in the feed and no impurities are adhered on the crystal surfaces at the end of DC. In the previous research, DC has been successfully applied to separate p-xylene from the mixed xylenes by Shiau et al. [1-3].

DC is introduced in this work to purify styrene (ST) from the mixture consisting of styrene (ST), ethylbenzene (EB), p-xylene (PX), m-xylene (MX) and o-xylene (OX). The experiments show that the purity of ST can be purified from 0.85 to 0.98 or from 0.90 to 0.99 in the mixture consisting of ST, EB, PX, MX and OX. Thus, DC provides an efficient separation method to separate ST from the mixture consisting of ST and the mixed xylenes. The recovery rate of ST in the experiments can be greatly improved by adjusting the operating temperature and pressure during the DC process.

[1] Shiau, L. D.; Wen, C. C.; Lin, B. S., 2005, ?Separation and purification of p-xylene from the mixture of m-xylene and p-xylene by distillative freezing?, Ind. Eng. Chem. Res. , 44(7), p.2258-2265

[2] Shiau, L. D.; Wen, C. C.; Lin, B. S., 2006, ?Application of distillative freezing in the separation of o-xylene and p-xylene?, A.I.Ch.E. Journal, 52(5), p.1962-1967.

[3] Shiau, L. D.; Wen, C. C.; Lin, B. S., 2008, ?Separation of p-xylene from the multicomponent xylene system by stripping crystallization?, A.I.Ch.E. Journal, 54(1), p.337-342.