2993. RUSSELL, W. W., AND MILLER, G. H. Catalytic Hydrogenation of Carbon Dioxide to Higher Hydrocarbons. Jour. Am. Chem. Soc., vol. 72, 1950, pp. 2446-2454.
Study was made of several types of Cu-activated, Co catalysts for the synthesis of higher hydrocarbons from CO2 and H2 at atmospheric pressure and in temperature range 175°-300°. Catalysts containing no alkali produced no liquid hydrocarbons or only traces but yielded small amounts after suitable poisoning. Alkalizing with K carbonate or phosphate, was necessary in order to produce catalysts active for liquid hydrocarbon synthesis and it appears that the alkali can act as a selective poison for CH4-forming catalyst centers. Small additions of Ce oxides to the alkalized catalysts were very effective in increasing synthesis life and catalyst stability. Although an alkalized, Ce-containing catalyst supported on a natural kieselguhr produced only CH4, when a flux-calcined kieselguhr was substituted as a support, a catalyst was obtained that synthesized nearly as much liquid hydrocarbons as unsupported catalysts of about the same composition. The optimum synthesis temperature was near 225°, but it depended on catalyst composition and activity. Raising synthesis temperature some 25°-100° for several hours produced a selective poisoning of catalyst hydrogenation centers, which caused a marked increase in liquid hydrocarbon formation upon resumption of synthesis at the initial temperature. While the CO theoretically available from the water gas reaction is in all cases ample to account for all of the higher hydrocarbons formed, it is entirely inadequate to account also for the amounts of CH4 formed. The maximum liquid hydrocarbon yield obtained was 95 ml. per m.3 of CO2 passed and was accompanied by 360 l. of gaseous hydrocarbons. The apparent activation energy for the overall synthesis was found to be 23.1 kcal.