(729b) Effect of Pt Dispersion On Observed Kinetics During Oxidations of H2, C3H6 and CH4 On Pt/Al2O3 Monolithic Catalyst

Joshi, S. Y. - Presenter, University of Houston
Ren, Y. - Presenter, University of Houston
Harold, M. P. - Presenter, University of Houston
Balakotaiah, V. - Presenter, University of Houston

It is well known that the catalyst activity decreases significantly because of aging. The dispersed catalytic species undergo coalescence or crystal growth induced thermally. As the crystals grow larger, they may block some of the pores, decreasing the effective diffusion coefficient of the reacting species in the washcoat. Moreover, as the sintering occurs, the pore openings may get smaller and pore diffusional resistance may become significant. As a result, the rate limiting step may shift from kinetic to pore diffusion control at low temperatures and the activation energy may be lower than that for the kinetic control. We investigate the effect of Pt dispersion on observed kinetics during oxidations of H2, C3H6 and CH4 on Pt/Al2O3 monolithic catalyst. Further, we quantify the relative contributions of kinetic and transport processes as a function of various design and operating conditions. This study follows a recent study (Chem. Engg. Sci. 65, 1729-1747) in which we developed criteria for characterizing various controlling regimes in catalytic monoliths in terms of various reactor and operating parameters.