Oxidative reforming of model biogas over NiO-Y sub(2)O sub(3)-ZrO sub(2) catalysts

Catalysts composed of NiO/Y sub(2)O sub(3)/ZrO sub(2) mixtures were synthesized by the polymerization method in a single step. They were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), physisorption of N sub(2) (BET) and X-ray photoelectron spectroscopy (XPS) and then tested in the oxidative reforming of a model biogas (1.5CH sub(4):1CO sub(2)) in the presence of oxygen (1.5CH sub(4) + 1CO sub(2) + 0.25O sub(2)) at 750 degree C for 6 h. It was observed that the catalysts Ni20YZ and Ni40YZ performed better in catalytic processes than NiO/ZrO sub(2) and NiO/Y sub(2)O sub(3), synthesized under the same conditions. The formation of Y sub(2)O sub(3)-ZrO sub(2) and NiO-Y sub(2)O sub(3) solid solutions increased the rates of conversion of the reactants (CH sub(4) and CO sub(2)) into synthesis gas (H sub(2) + CO). The formation of oxygen vacancies (in samples containing ZrO sub(2) and Y sub(2)O sub(3)) seemed to promote removal of the coke deposited on the nickel surface during the oxidative reforming of model biogas. The H sub(2)/CO ratios in the reaction products formed on the best catalysts were 1:1, which is desirable for their direct use in the STD and in the Fischer-Tropsch processes.