Catalytic bi-reforming of methane as a potential source of hydrogen rich syngas: Promotional effect of strontium on the catalytic performance of Ni/MgO-ZrO2

Bi-reforming of methane (BRM) has gained significant attention due to the escalating environmental concerns. This study investigates the performance of a monometallic Ni/MgO-ZrO2 catalyst with varying strontium (Sr) content from 0 to 10 wt% added to the 10 wt% nickel, employed in BRM. The synthesis of MgO-ZrO2 support was done by employing co-precipitation method, while both Ni and Sr metals were added via impregnation route. The physiochemical properties of the prepared catalysts were analyzed using various characterization techniques such as X-Ray Diffraction (XRD), N2-Physisorption Analysis, Temperature-Programmed Reduction (TPR), Temperature-Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). To assess the catalytic performance, the catalyst was tested in a fixed-bed continuous reactor using a reactant mixture of CH4, H2O, and CO2 in a ratio of 3:2:1 respectively, at a temperature of 800 °C. It was found that Ni-6 %Sr/ZrO2-MgO catalyst provided the optimum conversion rates for both CH4 and CO2 at 95.2 % and 85.7 % respectively, without significant deactivation observed even after 36 h of reaction. This excellent catalytic performance was attributed to several factors such as smaller metal particle size, improved metal dispersion, stabilization of t-phase in zirconia and the synergistic effects between the Ni and Sr particles. The spent catalyst characterization including XRD, FESEM and HRTEM shows that the addition of Sr significantly reduced carbon deposition. It also depicted that a stable and best performance of Ni-Sr/MgO-ZrO2 catalyst is ascribed to the production of filamentous carbon that has a crystalline nanotubular structure. On the contrary, the rapid deactivation of Ni/MgO-ZrO2 monometallic catalyst may be attributed to amorphous carbon.