(6h) Separation of P-Diethylbenzene from the Binary Diethylbenzene Mixture by Distillative Freezing

A new separation technique, called distillative freezing (DF), has been successfully applied to separate p-xylene from a liquid mixture of m-xylene and p-xylene (Shiau et al., 2005). Basically, DF is a distillative crystallization technology, which combines distillation and crystallization to result in pure crystals. The DF process is operated at triple point condition, in which the liquid mixture is simultaneously vaporized and solidified due to the three-phase equilibrium. It results in the formation of pure solid, and liquid phase and vapor phase of mixtures. The process is continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. p-diethylbenzene (p-DEB) is used as a crosslinking agent in the synthesis of polymeric resins and the desorbent in the Parex process for the separation of p-xylene from the mixed xylenes. To produce pure p-DEB, separation of p-DEB from the mixed DEB isomers is encountered in the production of p-DEB by the ethylbenzene alkylation. Due to close boiling temperatures of the mixed DEB isomers, it is rather complicated to separate them by distillation. The objective of this work is to investigate the feasibility of DF in separating the mixture of p-diethylbenzene (p-DEB) and m-diethylbenzene (m-DEB). The experiments show that p-DEB can be purified by DF from 95% to 99% or even from 90% to 99%. The experimental recovery rates are in the range 58~77%.

Shiau, L. D.; Wen, C. C.; Lin. B. S.,Separation and purification of p-xylene from the mixture of m-xylene and p-xylene by distillative freezing?Ind. Eng. Chem. Res. 2005, 44, P2258-2265.