Synergistic effects of Ni and CeO2 on ZSM-5 for enhancement of CO2 methanation at low temperatures

Methanation offers a potential option for converting CO 2 to green synthetic fuels, providing a solution for reducing carbon emissions. Nickel-based catalysts, promoted with CeO 2 and supported on zeolite ZSM-5, were synthesized for CO 2 methanation using different impregnation methods, including simultaneous and sequential impregnation of Ce 3+ and Ni 2+ salts onto the ZSM-5 zeolite (NiCe/ZSM-5, Ni-Ce/ZSM-5, Ce-Ni/ZSM-5). The effects of CeO 2 on Ni dispersion and crystallite size on ZSM-5 were investigated, revealing that simultaneous impregnation of Ce 3+ and Ni 2+ salts onto the ZSM-5 zeolite (NiCe/ZSM-5) leads to a higher effectiveness in creating smaller NiO and CeO 2 crystallite sizes compared to sequential impregnation. This approach enhanced Ni dispersion and increasing the basic sites of the catalyst. The samples were characterized using techniques such as X-ray diffraction (XRD), the surface areas and pore volumes measured by N 2 adsorption at 77 K (–196 °C), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), hydrogen temperature-programmed reduction (H 2 -TPR), and carbon dioxide temperature-programmed desorption (CO 2 -TPD). The CO 2 adsorption capacity at ambient pressure of different samples ranged from 0.31 to 0.48 mmol/g. Catalytic performance was evaluated via CO 2 conversion, CH 4 selectivity, CH 4 yield. Highest results were recorded for NiCe/ZSM-5, with 79.4 % conversion, 98.5 % CH 4 selectivity, and 75.6 % CH 4 yield at 375–400 °C. At 325 °C, the TOF of NiCe/ZSM-5 (0.319 s⁻¹) is 3.6 times higher than that of Ni/ZSM-5 (0.089 s⁻¹) prepared by the same method. The mechanism of the CO 2 methanation process was also proposed.