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 catalytic reaction was studied. In this simulation, no convection is assumed to simplify the analysis. The numerical model is as follows; A spherical platinum of 0.75 mm in radius is surrounded with the mixture. Three based partial differential equations, which govern mass, energy and species concentrations, are stated in one-dimensional polar coordinates. Axial symmetry, zero 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 catalytic reaction model. The adsorbed species are H, O, OH and H2O and 3 elementary surface reactions are used. As the results, a steady state is observed. The surface temperatures at the steady state do not depend on surface diffusion velocities but on adsorption rates and desorption rates. The catalytic ignition temperatures increase as H(s) surface diffusion velocity decrease. They are independent on surface diffusion velocities of O(s) and OH(s).