We present a combined computational and experimental approach to evaluate the suitability of the ITQ-12 nanoporous material (ITW) as a propane - Propylene separation device. For this, we have computed adsorption and diffusion of propane and propylene in the ITQ-12 zeolite. The propane isotherm is reproduced well, but the available propylene models in the literature are unable to describe the propylene isotherm. Newly developed force field parameters for propylene were obtained by fitting to our own experimental adsorption isotherms and validated with previous data taken from the literature. To obtain self-diffusion of propane and propylene in the zeolite, we combined the configurational-bias Monte Carlo method with rare-event molecular simulation techniques. Our results support experimental observations that point out ITQ-12 as a suitable structure for propane-propylene separation. The selectivity originates mainly from a difference in adsorption, possibly enhanced by a difference in diffusion.