D.I. Potemkin

On the Mechanism of CO and CO2 Methanation Over Ni/CeO2 Catalysts

The reactions of the CO and CO2 methanation in the excess of hydrogen were studied over Ni/CeO2 and Ni(Cl)/CeO2 catalysts prepared from nitrate and chloride precursors, respectively. Macrokinetic parameters of the CO and CO2 methanation over Ni/CeO2 and Ni(Cl)/CeO2 catalysts were determined. The nature of surface species during the CO and CO2 methanation over Ni/CeO2 and Ni(Cl)/CeO2 catalysts was studied by the Fourier transform infrared spectroscopy in situ technique. It was shown that the CO methanation proceeds similar ways over both Ni/CeO2 and Ni(Cl)/CeO2 catalysts via CO and H2 chemisorption on the surface of Ni particles. The CO2 methanation over Ni/CeO2 catalyst proceeds via the CO2 adsorption on the ceria surface and stepwise hydrogenation to methane through hydrocarbonate and formate intermediates by the hydrogen spilled over from Ni particles. With the Ni(Cl)/CeO2 catalyst, this reaction pathway is locked due to the ceria surface blockage by chlorine, to inhibit the CO2 methanation and therefore provide a high efficiency of Ni(Cl)/CeO2 catalyst in preferential CO methanation in the presence of CO2.

Избирательное окисление СО на биметаллических катализаторах Pt0,5M0,5 (M = Fe, Co, Ni), приготовленных из двойных комплексных солей

Nanopowders of Pt 0.5 M 0.5 (M = Fe, Co, Ni) alloys prepared by decomposition of complex binary salts [Pt(NH 3 ) 5 Cl][Fe(C 2 O 4 ) 3 ]·4H 2 O, [Pt(NH 3 ) 4 ][Co(C 2 O 4 )2(H 2 O) 2 ]·2H 2 O, [Pt(NH 3 ) 4 ][Ni(C 2 O 4 )2(H 2 O) 2 ]·2H 2 O, respectively, were studied in the reaction of selective CO oxidation. The bimetal catalysts were shown more active at low temperature than the Pt nanopowder. The catalyst activities decrease in the series of Pt 0.5 Co 0.5  Pt 0.5 Ni 0.5 > Pt 0.5 Fe 0.5 >>Pt. The observed high activity of bimetal Pt 0.5 M 0.5 catalysts at low temperature and considerable coverage of the Pt surface by adsorbed CO molecules may be accounted for by the activation of CO on the Pt atoms and O 2 on the second metal (Fe, Co, Ni) atoms and by the reaction localization on the Pt-M contacts on the alloy nanoparticle surface. The bimetal systems under study can be used for improving practically important catalysts for selective CO oxidation; they also are applicable for reburning of CO and hydrocarbons, hydrogenation, electrochemical reactions etc. The reported method for preparation of bimetal nanopowders based on the decomposition of complex binary salts is simple, does not need expensive reactants and can be easily adapted for synthesis of supported catalysts containing nanoparticles of metal alloys Pt 0.5 M 0.5 (M = Fe, Co, Ni).