Thoria- or molybdena-promoted Co/silica (alumina) catalysts were prepared by co-impregnation. The catalysts were characterized with temperature programmed reduction and temperature programmed surface reaction techniques and hydrogenation of carbon monoxide. Thoria enhanced not only the activity but also the selectivity of olefins and long-chain hydrocarbons. Molybdena effectively promoted only the activity, but did not alter the product distribution pattern. Thoria and molybdena exhibited a tendency to spread onto and to interact intimately with alumina; the promoting effects on alumina were much less pronounced than on silica.
