FTIR study of CO and NO adsorbed on nitrided CoMo/Al2O3 catalysts

Abstract

The states of surface Co and Mo sites on nitrided CoMo supported on Al₂O₃ were studied by adsorption of CO and NO as IR probe molecules. Three IR bands at 2200, 2060 and 2025 cm⁻¹ were detected for adsorbed CO. These bands can be respectively attributed to the surface NCO species as a result of CO adsorbed on surface N sites, and linearly adsorbed CO on surface Co and Mo sites in low valence states. The addition of cobalt to the Mo nitride diminishes the band at 2200 cm⁻¹. This may be due to either the change of the surface structure of the supported nitride, or the formation of a new phase, Co_xMo_yN_z, as suggested in the literature Kim etal., Catal. Lett., 1997, 43, 91 and Logan etal., Catal. Lett., 1998, 56, 165. Comparison of CO and NO adsorption on Mo₂N/Al₂O₃ and CoMoN_x/Al₂O₃ indicates that the presence of cobalt can promote the reduction and nitridation of Mo.