Hydrogen Rich Syngas Production over Ni Catalysts on Mg-stabilized Zirconia through Partial Oxidation of Methane: The Role of Magnesium as Stabilizer for Support & Active Sites.

Catalytic conversion of methane in the presence of O2 into hydrogen-rich syngas is known as partial oxidation of methane (POM). Achieving good H2 yield with H2/CO ~3 by using a low amount of Ni-based active sites at a low reaction temperature (~600 °C) through POM remains challenging. Herein, magnesia-stabilized zirconia (MSZ) is prepared by co-precipitation method by varying the amount of Mg from 8-14 mol%. Ni supported over MSZ catalysts are investigated for POM reaction and characterized by diffraction techniques, spectroscopic techniques, surface area-porosity, temperature-programmed reduction-oxidation, and thermogravimetry. The incorporation of magnesium stabilizes both the support and the active sites. Under the oxidizing environment, the strong interaction of NiO surmounts over moderate interaction. Upon incorporation of 14 mol% Mg into ZrO2 (14MSZ), the catalyst attains stable support and the largest surface area where most of the active sites are formed by "NiO under strong interaction". 5 wt % Ni dispersed over 14MSZ acquires the highest H2 yield (37%) and H2/CO ~3  at 600 °C and 85% H2 yield with ~2 H2/CO at 750oC. Over 5Ni/14MSZ catalyst, the high reaction temperature restricts indirect pathway of POM by limiting the CO2 yield and ensures high hydrogen yield through direct pathways of POM.