Oxygenates from syngas over highly dispersed cobalt catalysts

Highly dispersed cobalt metal catalyst has been prepared by the deposition of Co2(CO)8 on silicagel in an oxygen-free condition and has been characterized with EXAFS. This catalyst exhibited high activity for the formation of C+2 oxygenates from syngas without any modification. The formation of hydrocarbons was strongly suppressed and the selectivity of oxygenates, especially C2-oxygenates, was enhanced by the modification with alkali or alkaline earth cations. From the modification effects on CO hydrogenation and by the studies of in situ FT-IR, these basic cations were considered to reduce the hydrogenating ability of the catalyst by controlling the electronic state of the active cobalt site. Noble metals such as iridium and ruthenium have little effect on the catalyst of CO hydrogenation. Similar cobalt catalysts were prepared from Co2(CO)8 on other oxide supports and some oxides showed a similar effect on the basic additives. The effect of the cations and the reaction mechanism for the formation of oxygenates were discussed.