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

Abstract

Bi-reforming of methane (BRM) has gained significant attention due to escalating environmental concerns. This study investigates the performance of a monometallic Ni/MgO-ZrO2 catalyst with varying strontium (Sr) content ranging from 0 to 10 wt% added to the 10 wt% nickel, utilized in BRM. The synthesis of the MgO-ZrO2 support employed the 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 catalytic performance, the catalyst was tested in a fixed-bed continuous reactor using a reactant mixture of CH4, H2O, and CO2 in a 3:2:1 ratio, respectively, at a temperature of 800 °C. The Ni-6%Sr/ZrO2-MgO catalyst provided optimal 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, including smaller metal particle size, improved metal dispersion, stabilization of the t-phase in zirconia and synergistic effects between the Ni and Sr particles. The spent catalyst characterization including XRD, FESEM and HRTEM revealed that the addition of Sr significantly reduced carbon deposition. It also demonstrated that stable and best performance of the Ni-Sr/MgO-ZrO2 catalyst is ascribed to the production of filamentous carbon with a crystalline nanotubular structure. Conversely, the rapid deactivation of the Ni/MgO-ZrO2 monometallic catalyst may be attributed to amorphous carbon.