FTIR studies of CO chemisorption and reactivity on Rh/SiO2 catalysts promoted by niobium oxide

Abstract

(Rh + Nb)/SiO₂ catalysts were obtained by anchoring of nanometer size Rh particles on surface low-valent Nb^{n +} ions. These materials exhibit the following specific features compared to Rh/SiO₂: a low Rh surface coverage by chemisorbed hydrogen and carbon oxide; a high-frequency shift of linear CO absorption band and appearance of two absorption bands of a C- and O-bonded CO at 1704 and 1652 cm⁻¹. On exposure to H₂, the stability of surface carbonyls increases in the sequence: Rh-CO-Nb^{n +} < Rh-CO ≤ Rh₂(CO) < Rh⁺(CO)₂. The possible role of C- and O-bonded CO complexes in the conversion of syngas on supported rhodium catalysts promoted by transition element oxides is discussed.