Synthesis of NiO–MgO–ZrO2 catalysts and their performance in reforming of model biogas

Catalysts containing NiO/MgO/ZrO2 mixtures were synthesized by the polymerization method in a single step. They were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and physisorption of N2 (BET) and then tested in the reforming of a model biogas (1.5CH4:1CO2) in the presence of air (1.5CH4 + 1CO2 + 0.25O2) at 750 °C for 6 h. It was observed that the catalyst Ni20MZ performed better in catalytic processes than the well known catalysts, Ni/ZrO2 and Ni/MgO, synthesized under the same conditions. The formation of solid solutions, MgO–ZrO2 and NiO–MgO, increased the rate of conversion of reactants (CH4 and CO2) into synthesis gas (H2 + CO). The formation of oxygen vacancies (in samples containing ZrO2 and MgO) seems to promote removal of the coke deposited on the nickel surface. The values of the H2/CO ratio were generally found to be slightly lower than stoichiometric, owing to the reverse water–gas shift reaction occurring in parallel.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (145 K)Download as PowerPoint slideHighlights► The NiO–MgO and the MgO–ZrO2 solid solutions were obtained. ► The addition of MgO stabilized the tetragonal phase of zirconia and originated oxygen vacancies. ► Solid solutions help to increase the activity of catalysts. ► Oxygen vacancies seems to promote removal of the carbon deposited. ► NiO–MgO–ZrO2 catalysts are active in model biogas reforming.