Syngas production by means of biogas catalytic partial oxidation and dry reforming using Rh-based catalysts

•Beneficial effect of adding O2 to the dry reforming of biogas using Rh catalysts.•Higher activity and stability of Rh catalysts under oxy-CO2 conditions.•Higher CH4 conversions and hydrogen yields with O2/CH4 molar ratios up to 0.45.•Rh/Al2O3 catalysts outperformed Rh/SiO2, Rh/CeO2 and Pt/Al2O3.•Moderate coke formation of various types at 700°C even at high GHSV.