Modelling of selective NOx reduction on Ce/In-promoted sulfated zirconia catalysts

Various pseudohomogeneous models for the selective catalytic reduction of NO, by methane were developed by considering reaction schemes and kinetic mechanism. The models were applied to predict the performance of Ce/In-promoted sulfated zirconia catalysts in a wide temperature range from 300 to 700degreesC in a fixed bed reactor assuming plug-flow. A nonlinear kinetic model fits the experimental data better than a simple linear model. The mass balance differential equations were solved numerically. The model parameters were estimated by the Simplex-method of Nelder-Mead with a fourth order Runge-Kutta-Merson-method. The finally chosen model is better suited for the prediction of the In-free catalysts than for the mixed oxide catalysts or the Ce-free catalysts. The model suggests that CO formed in the process plays no role in the reduction of NO by CH4. This was confirmed by experimental evidence. The investigated Ce/In zirconia system was better suited for NO reduction by CH4 than those published previously [1].