Hydrogenation of carbon monoxide over highly dispersed cobalt catalysts derived from cobalt(Ⅱ) acetate

摘要

Highly dispersed cobalt metal catalysts supported on SiO_2 were prepared by using cobalt(Ⅱ) acetate as a precursor promoted with noble metals such as Ir, Ru, Rh, Re, Pt or Os. The catalysts were active for the formation of oxygenates by CO hydrogenation and the vapor phase hydroformylation of ethene. The selectivity of oxygenates, especially C_2-oxygenates, was strongly enhanced by a further modification with basic additives such as alkali and alkaline earth cations. By the characterization of the catalysts using XPS, EXAFS, XRD, FT-IR, etc., it is revealed that highly dispersed Co~(2+) particles are formed on SiO_2 by the decomposition of Co(Ⅱ) acetate at an elevated temperature in flowing H_2. The noble metals promote the reduction of the Co~(2+) particles to cobalt metals by spilt-over hydrogen activated on the noble metal sites. The effects of the basic additives were discussed.