An numerical simulation of effect of surface diffusion on hydrogen-oxygen reaction over platinum catalytic surface

An numerical simulation of hydrogen-oxygen reaction over platinum catalytic surface was carried out and the effect of surface diffusion velocity on ca talytic reaction was studied. In this simulation, no convection is assumed to simplify the analysis. The numerical model is as follows; A spherical pl atinum of 0.75 mm in radius is surrounded with the mixture. Three based par tial differential equations, which govern mass, energy and species concentr ations, are stated in one-dimensional polar coordinates. Axial symmetry, ze ro azimuthal velocity, and no gradient along the axis are assumed. Because of low Mach numbers, constant pressure is assumed, and therefore, momentum equation is not used. The Langmuir-Hinshelwood mechanism was used for the c atalytic reaction model. The adsorbed species are H, O, OH and H2O and 3 el ementary surface reactions are used. As the results, a steady state is obse rved. The surface temperatures at the steady state do not depend on surface diffusion velocities but on adsorption rates and desorption rates. The cat alytic ignition temperatures increase as H(s) surface diffusion velocity de crease. They are independent on surface diffusion velocities of O(s) and OH (s).