The experimental adsorption and desorption rate data for pure propylene, pure propane, and propylene-propane mixtures on 13 X molecular sieves are presented for different temperatures and compositions; these rate data were efficiently determined using the differential sorption bed system described by Liapis et al. (Liapis et al. (1992) Rates and equilibria of adsorption and desorption of propane and propylene on 13 X molecular sieves determined experimentally using a differential sorption bed system. Sep. Technol. 2, 141-154). Propylene is the most preferentially adsorbed component, and the desorption rates of propylene and propane are slower than the adsorption rates. Mathematical models were constructed and solved, and it was found that the two-component model could provide a quantitative measure of the interactions between propylene and propane, and could describe the behavior of binary adsorption kinetics including the overshoot of the equilibrium loading by the less preferentially adsorbed propane. The theoretical results indicate that the desorption rates are not described by the same intracrystalline diffusion coefficients as the adsorption rates.