Characterisation and activity evaluation of silica supported cobalt and ruthenium catalysts

We prepared Co/SiO2, Co-Ru/SiO2 and Ru/SiO2 catalysts by ion-exchange method in an attempt to obtain well dispersed active sites. The catalysts were characterised by chemisorption, oxygen titration, TPD and XPS, and their activity was evaluated in CO hydrogenation. The results showed that the Co/SiO2 catalyst exhibited a very low extent of reduction, and consequently its hydrogen uptake and activity were very low. In case of CoRu/SiO2, the hydrogen and CO uptake was far much higher than for the physical mixture or for the sum of Co/SiO2 and Ru/SiO2. Evidently, ruthenium acted as a reduction aid to cobalt in the bimetallic system. Yet, irrespective of the highest uptakes of the CoRu/SiO2 system, the highest activity in CO hydrogenation was obtained with the Ru/SiO2 catalyst. The synergistic performance of the CoRu catalyst was, however, evidenced by the unusually high formation of methanol - a novel finding which indicates that neither of the metals was present as a purr entity in the bimetallic system. (C) 1998 Elsevier Science B.V. All rights reserved.