The Role of Active Sites of CoH-ZSM-5 Catalysts for the C2H4-SCR of NO

Abstract

The selective catalytic reduction of NO with ethylene was investigated and compared over fresh CoH-ZSM-5, H2-reduced (450 °C) CoH-ZSM-5 and H-ZSM-5. The dispersion of cobalt species for fresh and H2-reduced CoH-ZSM-5 was studied by UV–vis and FTIR spectra. Combined with DRIFTS results of ad-species and reaction experiments, the active sites of CoH-ZSM-5 for the C2H4-SCR were identified and the catalytic functions of active cobalt species and support were also clarified. Notably, the formation of –CN or –NCO species was heavily dependent on the type of nitrates. Co3O4 particles contributed to the oxidation of NO to bidentate nitrates. The latter species were crucial for the formation of –NCO. Whereas exchanged Co2+ ions facilitated the oxidation of NO to monodentate and/or bridged nitrates which participated in the formation of –CN species. The active sites of CoH-ZSM-5 for the C2H4-SCR of NO were identified and the catalytic functions of active cobalt species and support were also clarified. Co3O4 particles contributed to the oxidation of NO to bidentate nitrates, the latter species were crucial for the formation of –NCO. Whereas exchanged Co2+ ions facilitated the oxidation of NO to monodentate and/or bridged nitrates which participated in the formation of –CN species .