SEPARATION OF BENZENE-CYCLOHEXANE MIXTURES BY PERVAPORATION.

The separation of liquid mixtures of benzene and cyclohexane which form an azeotrope at a composition of 51. 8 wt% benzene at atmospheric pressure has been investigated by pervaporation using six different kinds of polymeric membranes. The membranes studied were of polyethylene, polypropylene, X-nylons and Ionomer Surlyns. A specially designed pervaporation cell was used to study the permeation rates and selectivities in the temperature range from 30 to 60 degree C. The rate of pervaporation increased with temperature, and it was found that the temperature dependence of the rate for both pure components and mixtures could be expressed by Arrhenius-type relationships. However, the selectivity expressed by a separation factor decreased with increasing temperature. The pervaporation rate greatly varied with the composition of the feed mixtures, while the selectivity was weakly dependent on the composition, but decreased slightly with an increase in concentration of benzene in the feed.