A LOW-TEMPERATURE IR SPECTROSCOPIC STUDY OF SELECTIVE ADSORPTION OF NO AND CO ON CUO/GAMMA-AL2O3

The composition of the crystal phase and the valence state of surface copper ions was measured by XRD and XPS methods on a CuO/γ-Al2O3 catalyst. It was concluded that the bulk phase was composed of CuO and CuAl2O4, and Cu2+ and Cu+ ions coexisted on the surface, although the sample was oxidized in oxygen atmosphere. The infrared spectra of CO, NO, and (CO + NO) adsorbed on this catalyst were recorded from 123 to 173 K. All infrared bands were assigned. The adsorption experiment of CO and NO also demonstrated that Cu2+ (CuO and CuAl2O4) and Cu+ ions coexisted on the surface. CO or NO could be adsorbed on Cu2+ and Cu+ sites below 173 K, but CO was only adsorbed on Cu+ sites and NO only on CU2+ sites over 173 K. The alternate adsorption and coadsorption of NO and CO found that CO was selectively adsorbed on the Cu+ sites (2120 cm-1 band) and NO was selectively adsorbed on the Cu2+ sites (1888 cm-1 on CuO and 1862 cm-1 on CuAl2O4), when CO and NO coexisted in the gas phase. © 1991.