Separation of mono‐ and dibranched hydrocarbons on silicalite

Abstract Breakthrough curves for mixtures of C5 and C6 hydrocarbons with different degrees of branching were obtained experimentally on a silicalite molecular sieve by fixed‐bed experiments. The kinetic separation of di‐ from monobranched hydrocarbons was feasible on this type of zeolite: dimethyl molecules enter silicalite crystals very slowly, whereas monomethyl molecules are quickly adsorbed. Experimental results were compared to a theoretical isothermal model, considering the variation of diffusivity with concentration according to the Maxwell–Stefan theory. The parameters of the model (adsorption equilibria and diffusivities) were determined from single‐component breakthrough curves. Experimental curves were generally well represented by the model, but the variation of diffusivity with concentration, as predicted by the Maxwell–Stefan theory, did not significantly improve the model prediction of experimental breakthrough curves by using a mean value of diffusivity.