Partial Oxidation of Bio-methane over Nickel Supported on MgO-ZrO2 Solid Solutions

Syngas can be produced from biomethane via Partial Oxidation of Methane (POM), being an attractive route since it is ecofriendly and sustainable. In this work, catalysts of Ni supported on MgO-ZrO2 solid solutions, prepared by a one-step polymerization method, were characterized by HRTEM/EDX, XRD, XPS, H-2-TPR, and in situ XRD. All catalysts, including Ni/ZrO2 and Ni/MgO as reference, were tested for POM (CH4:O-2 molar ratio 2, 750 degrees C, 1 atm). NiO/MgO/ZrO2 contained two solid-solutions, MgO-ZrO2 and NiO-MgO, as revealed by XRD and XPS. Ni (30 wt%) supported on MgO-ZrO2 solid solution exhibited high methane conversion and hydrogen selectivity. However, depending on the MgO amount (0, 4, 20, 40, 100 molar percent) major differences in NiO reducibility, growth of Ni-0 crystallite size during H-2 reduction and POM, and in carbon deposition rates were observed. Interestingly, catalysts with lower MgO content achieved the highest CH4 conversion (similar to 95%), high selectivity to H-2 (1.7) and CO (0.8), and low carbon deposition rates (0.024 g (carbon center dot)g(cat)(-1) h(-1)) with Ni4MgZr (4 mol% MgO) turning out to be the best catalyst. In situ XRD during POM indicated metallic Ni nanoparticles (average crystallite size of 31 nm), supported by MgO-ZrO2 solid solution, with small amounts of NiO-MgO being present as well. The presence of MgO also influenced the morphology of the carbon deposits, leading to filaments instead of amorphous carbon. A combustion-reforming mechanism is suggested and using a MgO-ZrO2 solid solution support strongly improves catalytic performance, which is attributed to effective O-2, CO2 and H2O activation at the Ni/MgO-ZrO2 interface.

Automated summary

In this study, catalysts of Ni supported on MgO-ZrO2 solid solutions were prepared and characterized. The Ni(30 wt%) supported on MgO-ZrO2 solid solution exhibited high methane conversion and hydrogen selectivity. The catalyst with a 4 mol% MgO content, Ni4MgZr, showed the best catalytic performance.