Hydrogenation of CO2 over SiO2 Supported Rh-Co-alkalimetal Catalysts

Hitoshi KUSAMA* and Hironori ARAKAWA

Photoreaction Control Research Center, National Institute of Advanced Industrial Science and Technology; AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba-shi 305-8565 Japan

CO2 hydrogenation was carried out over alkali metals such as Li, Na and K promoted silica-supported Rh-Co catalysts (Rh-Co-M/SiO2). Na additive was most effective of the three alkali metals for ethanol formation over 5 wt% Rh-Co (1 : 1) /SiO2. The added amount of Na influenced product selectivity as well as CO2 conversion. The highest ethanol selectivity was obtained over 5 wt.% Rh-Co-Na (1 : 1 : 0.5)/SiO2 catalyst. The mechanism of promotion effect of Na added amount was investigated by means of in situ FT-IR observation during reaction. The variation of Na added amount changed the ratio of Rh2-(CO)3 and bridged type adsorbed CO species to linear type one. This finding suggested that the amount of Na affected on the hydrogenation ability of Rh-Co/SiO2 catalysts, leading to the difference in CO2 hydrogenation activity.

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