FAST AND SLOW METHANATION PATHWAYS IN HYDROGENATION OF CARBON-DIOXIDEON FE-MN OXIDE CATALYSTS

The hydrogenation of CO2 on Fe-Mn oxide catalysts (pure or doped with Rh and La) was investigated in pulse and continuous flow experiments. The maximum methanation rate observed in the short initial period of r eaction on freshly reduced catalyst was attributed to the fast reactio n pathway, connected with reactive chemisorption of CO2. The slow meth anation pathway was related to the formation of carbonaceous deposits on the catalysts (observed even in pulse experiments). A correlation b etween maximum methanation rate and the content of the reactive deposi t in continuous flow was established. Another, less reactive deposit, which required a higher temperature to be hydrogenated, was also obser ved. The effect of Rh and La on activity and selectivity of the cataly sts was investigated. Rh enhances fast methanation while La substantia lly decreases rate of both reaction pathways. The same effects were ob served during hydrogenation of carbon deposits.