In situ studies of supported rhodium catalysts

Abstract

Rhodium catalysts have been prepared, supported on γ-alumina, vanadium(III) oxide, chromia and molybdena. The activity and selectivity of these materials in the conversion of synthesis gas, (H2/CO: 1/1, 523 K and 5 bar pressure), to methanol, ethanol and hydrocarbons has been studied. All catalysts showed similar activity except for chromia, which was almost inactive at the temperature chosen. Selectivity to higher oxygenates followed the trend: V2O3 > MoO3 > Al2O3 > Cr2O3. The alumina supported catalysts had the highest selectivity to methanol. Catalysts have been characterised in situ by extended X-ray absorption fine structure (EXAFS) and the alumina-supported material has been examined in the greatest detail. On reduction at 473 K, rhodium particles with diameter 30 A diameter, on the chromia support.The relation between catalyst structure and performance is discussed.