Study on the correlation between the surface active species of Pd/cordierite monolithic catalyst and its catalytic activity

Two Pd-loading routes and three Pd-precursor matters were adopted to prepare Pd/(Ce,Y)O₂/γ-Al₂O₃/cordierite monolithic catalyst. The surface active species on the catalyst were characterized by XPS, and its catalytic activity for methane combustion was tested, and the dynamics of the catalytic combustion reaction was also discussed. Pd-loading route and Pd-precursor mass have a significant influence on the catalytic activity and surface active species. The sol dipping method is more advanced than the aqueous solution impregnating method. PN-sol catalyst, by sol dipping combined with Pd(NO₃)₂-precursor, has the best catalytic activity. The physical reason is the unique active Pd phase coexisting with active PdO phase on the surface, and thus the Pd3d_5/2 binding energy of surface species and apparent activation energy of combustion reaction are considerably decreased. The catalytic activity index, Pd3d_5/2 binding energy and apparent activation energy are highly tied each other with exponential relations.