HYDROGENATION OF CO2 AND CO BY FE CATALYSTS OBTAINED FROM FE-2(CO)(9)AND FE-3(CO)(12) CLUSTERS SUPPORTED ON ACTIVATED CARBONS

Hydrogenation of carbon dioxide and carbon monoxide on iron catalysts prepared from Fe-2(CO)(9) and Fe-3(CO)(12) supported on four activated carbons were studied. The catalysts, prepared and reduced in H-2 at 6 73 K for 12 h, were characterized by H-2 and CO chemisorption and TEM. The catalysts prepared from Fe-3(CO)(12) had higher dispersion. The d ispersion increased with increasing meso- and macropore volumes of the activated carbon. Hydrogenation of CO2 produced CH4 and CO, the rate of methane formation being much lower than that of CO formation; and b oth rates remained constant during reaction. However, in the hydrogena tion of CO, the rate of methane formation and the CO conversion decrea sed with increasing reaction time, and hydrocarbons up to butane as we ll as CO2 were detected among the reaction products. The differences f ound between the CO2-H-2 and the CO-H-2 reactions could be due to the different concentrations of CO surface species and to the possibility of the formation of metal oxides as a result of CO2 dissociation.