Separation of alkane isomers by exploiting entropy effects during adsorption on silicalite-1: A configurational-bias Monte Carlo simulation study

We discuss and develop an entropy-driven principle for separating isomers o f alkanes in the five to seven carbon atom range by adsorption on silicalit e-l. The normal alkanes are preferentially adsorbed because of configuratio nal entropy effects; they "pack" more efficiently within the channel struct ures of silicalite. To demonstrate the separation principle we carried out CBMC simulations to determine the isotherms of various mixtures of linear a nd branched alkanes in silicalite-l. We show that the configurational entro py effects manifest at loadings greater than 4 molecules/unit cell and the sorption favors the linear alkanes while the branched alkanes are virtually excluded from the silicalite matrix. Validation of the entropy-based separ ation principle is obtained by analyzing the silicalite membrane permeation data published in the literature.