Numerical study of the diffusion of binary hydrocarbon blends in ZSM-12 zeolites

Abstract The experimental results for the simultaneous diffusion of toluene and ethylene in one dimensional channels of the ZSM-12 zeolite which have been reported in a previous publication are fitted with an original finite difference numerical simulation model. This system is mimicking the single file diffusion of hydrocarbons in the zeolite passive hydrocarbon trap installed at the exhaust of an internal combustion engine, prior to the catalytic muffler, to solve the hydrocarbon cold start emission problem. The study encompasses the effects of Na+, H+ and Ag+ counterions and temperature ramp on the temperature programmed desorption of the binary mixture. A simple lattice gas model is proposed to simulate the binary gas diffusion in a one dimensional pore lattice. Numerical simulations show that taking into account an Arrhenius dependence of the binary gas diffusion coefficient on temperature yielded a good fit of these experimental results, explaining many significant features of the temperature programmed desorption profile observed experimentally.