Simulation of the depollution process by catalytic combustion at porous pellet catalyst level

The objective of this work is the investigation of the catalytic combustion process of oxylene vapors in a porous pellet of 0.5% wt Pt/alumina catalyst, under conditions similar to those used for de-pollution applications. Uniform and non-uniform Pt distributions in the grain volume were analyzed and compared. Platinum utilization efficiency was expressed through the internal effectiveness factor and to o-xylene conversion. Calculations have shown that, for o-xylene vapors concentrations similar to the ones used in decontamination applications, among the physical phenomena, internal diffusion presents the most important influence on the process kinetics. Also, important effects on the overall process kinetics could present the external concentration and temperature gradients, especially for Pt non-uniform distributions. Moreover, the calculation evidenced a negligible internal temperature gradient and confirmed the principle stating that the maximum efficiency is obtained when Pt is placed in a narrow zone in the proximity of the external surface of the porous pellet.