AN IR SPECTROSCOPIC STUDY OF THE REACTION KINETICS OF SURFACE CARBONYL AND FORMATE SPECIES ON SUPPORTED Os CATLYST

Based on the quantitative measurement of IR absorption band, the comparison of reaction rates between existance carbonyl (or formate) species and H₂ (or H₂O) was performed on a K₂OsO₂(OH)₄ -derived Os/γ-Al₂O₃ catalyst. Following views are evidenced: 1) Due to the existance of osmium the reactivity of surface formate species is extremely improved, in spite of that the species are probably adsorbed on support surface.. It may attribute to the active adsorption of H₂ or H₂O. 2) The reaction of HCO₂^- with H₂ is faster than that or CO species with H₂ at 473K. IR spectra directly confirmed that one of the product is CO. The reaction of HCO₂^- with H₂ may be the reverse reaction of CO adsorption. Because the reaction of CO hydrogenation has not taken place at such low temperature, it is considered that formate species may not be the intermediate of CO hydrogenation at this temperature. The reaction rate could not be compared at higher temperature (573K). 3) The reaction of HCO₂^- with H₂O would not oceur at as low as 323K. The reaction rate of HCO₂^- species with H₂O at 473K is faster than that of carbonyl with H₂O at 473K. When H₂O was substituded by D₂O, same conclusions were obtained. It is considered that formate species is an intermediate or WGS reaction.