Separation of Liquid through Polymer Membrane. Benzene and Cyclohexane System

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Abstract
Separation of benzene-cyclohexane liquid mixture by permeation through Methocel HG (hydroxypropyl-methyl cellulose) membranes was studied using the pervaporation mode. The separation factor and permeation rates for benzene in Methocel HG are found to be strongly dependent upon the concentration of benzene in the benzene-cyclohexane mixtures. The separation factor for benzene versus cyclohexane was found to be at least 200 in the case of benzene-cyclohexane liquid mixtures with a 50/50 weight ratio. Addition of Schardinger α-dextrin into the Methocel HG membrane increases the relative solubility for benzene versus cyclohexane, but decreases the permeation rates and separation factor for the benzene-cyclohexane permeation system. Thus the reverse of separation of benzene-cyclohexane in the Methocel HG membrane was found when the Methocel HG membrane contained more than 25% Schardinger α-dextrin. The mechanism of this drastic effect is explained in terms of induced tortuous diffusion and the reduction of the self-plasticizing effect of benzene in the membrane permeation.