Interplay between Acidity-Basicity and Metal-Support Interactions on Hydrogen Production and Coke Resistance of Ni-Co Catalysts for Dry Reforming of Methane: Influence of Support

The hydrogen production from biogas via dry reforming has gained importance, as it is a renewable feedstock that contains methane and carbon dioxide. Despite nickel being an effective catalyst, it produces a low hydrogen purity and suffers from coke deposition. The synergistic effects of acidity/basicity, metal-support interactions, lattice oxygen, and oxygen vacancies on reactant conversion, H 2 /CO ratio, and resistance to coke deposition were not explored until now. In this study, wetness-impregnated Ni and Ni-Co catalysts on α- and γ-alumina were synthesized and characterized using different techniques. The catalysts’ performance was evaluated in a packed bed reactor between 600 and 700°C, 20000 and 30000 mL gcat⁻¹ h⁻¹ gas hourly space velocity (GHSV), and CH 4 :CO 2 ratios of 1 and 1.5. The highest methane and carbon dioxide conversions were 91.5% and 81.2% over Ni-Co/γ-Al 2 O 3 with an H₂/CO ratio of 3.3 due to a high acidity and basicity. The coke deposited was the highest for Ni-Co/γ-Al 2 O 3 due to a lower fraction of lattice oxygen and strong metal-support interactions (SMSI). The coke deposited over the Ni-Co/γ-Al 2 O 3 catalyst was reactive, which can be removed at an 80°C lower temperature than the others. A higher fraction of lattice oxygen in Ni/γ-Al 2 O 3, Ni/α-Al 2 O 3, and Ni-Co/α-Al 2 O 3 catalysts resulted in a lower coke. The Ni-Co catalyst, with a lower acidity-to-basicity ratio per m² (<0.07), showed very high metal dispersion and resulted in an H₂/CO > 3. The Ni-Co/γ-Al 2 O 3 catalyst was stable over a 48-hour time-on-stream. Ni-Co/α-Al 2 O 3 catalyst undergoes deactivation due to sintering.