In situ FTIR study of CO–H2 reactions over RH/TiO2 catalysts at high pressure and temperature

Abstract

IR spectra are reported of Rh/TiO₂in situ in CO–H₂ mixtures (1 : 14, 1 : 2, 2 : 1 and 14 : 1 ratios) at high pressure (0.3 or 1.5 MN m^–2) and temperature (473, 523 or 553 K). The spectra allowed the surface hydroxy groups and water on TiO₂, CO adsorbed on Rh and gaseous CO, CO₂ and CH₄ to be monitored together with OMe^–, OEt^–, HCO₂^– and MeCO₂^– species on TiO₂ and surface CH₂-containing hydrocarbon.

Titania alone catalysed the CO–H₂ reactions but the dominant products with Rh/TiO₂ were formed by catalysis over Rh followed by spillover of oxygenates onto the support. Surface carbonyl and carbonyl hydride complexes of rhodium, present during the reaction, are believed important, possibly as precursor intermediate species influencing the catalytic selectivity for methanol, ethanol, methane and higher linear hydrocarbon production.