COMPARISON OF CARBON-DIOXIDE AND CARBON-MONOXIDE WITH RESPECT TO HYDROGENATION ON RANEY RUTHENIUM CATALYSTS

On Raney ruthenium catalysts pretreated with a mixed gas of water vapo r and helium, the rate of hydrogenation of CO2 was higher by three ord ers of magnitude than that of the hydrogenation of CO. However, the fo rmer reaction gives methane almost exclusively, while the latter react ion can give methanol. Since supported ruthenium catalysts usually cat alyze both hydrogenations of CO and CO, with almost the same rate, Ran ey ruthenium catalysts were shown to be uniquely active for hydrogenat ion of CO2 under the conditions studied here. The weight-based activit y of methane production from CO2 and hydrogen is much higher than that of the supported catalysts at 353-413 K and under 80 kPa. Methanol wa s also produced from CO2 on Raney ruthenium catalysts, though the sele ctivity was negligibly lower than that from CO. With the mixtures of C O, CO2, and H-2 at 353 K and under 80 kPa, CO was preferentially hydro genated, unless composition of CO was very small. Reaction mechanisms of CO-CO2 hydrogenation are proposed.