Catalytic combustion of methane in a monolith washcoat: Effect of water inhibition on the effectiveness factor

This paper reports the results of a numerical investigation of the diffusio n and reaction of methane in the washcoat of a catalytic monolith reactor. The kinetic rate expression used is an empirical equation determined experi mentally for a palladium oxide catalyst. The effect of water inhibition on the reaction rate is included in the model. A multi-species diffusion and r eaction model is used to simulate the process. The model is solved in a 2-D space using a finite element method. It is observed that the inhibiting ef fect of water tends to lower the observed reaction rate and that a higher s urface water concentration results in an increase in the observed effective ness factor. The effectiveness factor depends on three dimensionless parame ters. Strong diffusion limitation can lead to high water concentrations at the interior of the catalytic washcoat.