Effect of the Pt/Co ratio upon the catalytic behavior of PtCoFerrierite washcoated on cordierite monoliths

CoFER and PtCoFER were prepared with different Co loadings and Co/Pt ratios. The resulting powders were washcoated on ceramic honeycombs. To increase adherence, silica was added to the slurry as a binder. The samples were assayed for the SCR of NOx with methane in excess oxygen. The maximum conversion of NOx to N2 for each formulation when plotted versus either Co loading or Co/Pt ratio presented maxima. All catalysts partially deactivated with 2% water. A thorough TPR, XPS and LRS characterization of fresh and deactivated catalysts showed that two deactivation mechanisms are operative. At low Co loadings, the formation of Pt clusters is responsible for the low selectivity, while for higher loadings Co3O4 is formed and is the non-selective species.