Activity and stability of powder and monolith-coated Ni/GDC catalysts for CO2 methanation

The methanation of CO2 via the Sabatier process is gaining interest for power-to-gas (P2G) application. In this work, CO2 methanation activity and stability were investigated over Ni/GDC (gadolinium-doped-ceria) catalysts at atmospheric pressure varying reaction temperature (TSET=300-600 °C) and space velocity (GHSV=10,000-50,000 h-1). Powder catalysts with different Ni content (15-50 wt.%) were synthesized by the solution combustion synthesis (SCS). The same method was adopted to in situ deposit the Ni/GDC (50 wt.%Ni) coating layer on the cordierite monolith (500 cpsi). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Temperature profiles along the structured catalytic bed were discussed to interpret the experimental results. Catalytic performance increased by increasing the Ni content due to enhanced metal-to-support interaction, basicity and oxygen vacancies. Uniform, thin and high-resistance catalytic layers were in situ deposited on the cordierite monoliths by the fully reproducible SCS method. Structured catalysts showed high methane productivity per unit weight of catalyst due to simultaneous low catalytic loading and high flow rate. Excellent stability was observed over 200 h of time-on-stream. The results reported in this manuscript pinpointed on the important aspects of realizing CO2 methanation on structured catalysts, providing a platform for further optimization studies.