Scientific Papers in SCI

The properties of prereduced (10%Co + 0.5%Pd)/Al2O3 (TiO2) systems in the CO hydrogenation reaction at atmospheric and high pressure were studied. At atmospheric pressure, alumina-supported catalysts were more selective toward methane but those using titania were more active. Alumina containing samples demonstrated high temperature H-2 desorption, firmly held surface carbonate species, high tendency to agglomeration. During the reaction metal surface reconstruction and increased formation of CH2 groups occurred being more pronounced with titania-supported catalysts. Stability tests at 250 degrees C showed opposite behaviour of both systems. Monodentate carbonate intermediates adsorbed on sites of moderate strength prevailed on titania samples, while formate species predominated on high strength sites of alumina-supported catalysts. High pressure catalytic tests revealed dependence of activity on T-red, synthesis of C2+ hydrocarbons, decreased CO2 production, a higher CH4/CO2 ratio for alumina containing system. Due to SMSI, increased CO2 production on titania samples was preserved. Titania-supported catalysts revealed a stronger decrease of CO conversion rising T-red while alumina catalysts had almost unchanged activity. CO conversion decreased with time due to difficulties in surface diffusion of reagents/intermediates/products and metal particle agglomeration. Concerning T-red comparison of product distribution showed a steady trend. Because of stable CO and CHx surface species, titania containing catalysts produced lower content of C5+ compounds. Alumina-supported samples showed a higher selectivity to C5+ compounds at the expense of methane. A higher selectivity ratio for CH4 and CO2 determined in catalytic CO hydrogenation over a certain catalyst at atmospheric pressure could indicate that a given sample is predisposed to form C2+ hydrocarbons at a higher pressure.

Fischer-Tropsch (FTS) reaction is a well-known catalytic process for the conversion of synthesis gas into liquid fuels. The addition of a water gas shift (WGS) catalyst to the FTS one has been postulate to notably increase the efficiency of the process. In order to investigate this issue, we conducted the FTS reaction over a Co-Re/Al2O3 catalyst combined with an optimal WGS Pt/CeO2 catalyst. We observed a notable increase of CO conversion in presence of the Pt/CeO2 catalyst that a priori could be attributed to the WGS reaction. However, the WGS reaction is unfavourable at pressures higher than 1 bar and CO/CO2 hydrogenation over Pt/CeO2 could be more favoured under FTS reaction conditions. In order to gain insights on this fact and elucidate the role of Pt/CeO2 in the FTS reaction we have performed an operando DRIFTS-MS study under close FTS reaction conditions at 4 bar over the Pt/CeO2 catalyst.