Infrared spectroscopic study of the adsorption of CO, CO2 and NO on fluorinated alumina and supported Molybdenum–Nickel catalysts

Abstract

Adsorption of CO, CO₂, NO and O₂ probe molecules has been used to study the surface of fluorinated alumina and of supported Mo–Ni catalysts. Addition of F to alumina drastically inhibited formation of carbonates from CO (at 673 K) and CO₂(at room temperature) adsorption and also inhibited the formation of nitrates from NO adsorption at room temperature. Reduction with H₂(773 K) followed by O₂ and NO adsorption at low temperatures suggest that the active-phase Mo–Ni is more highly dispersed in the catalyst with higher F content. These data are in agreement with spectroscopic results for NO adsorption. This effect of F on the degree of metallic dispersion is probably associated with the anchoring of the polymeric ion Mo₇O₂₄^6– to the support, which is highly unfavoured by the partial substitution of hydroxyl groups by F^–.