The promoting effect of magnesium on NiMgLaZr catalysts for biogas upgrading to syngas via a tri-reforming process

Abstract

The effect of partial substitution of lanthanum by magnesium on the catalytic activity of the Ni-La2Zr2O7 catalyst in the biogas tri-reforming reaction was studied. Four catalysts, Ni-La2-xMgxZr2O7-δ (x = 0.25, 0.5, 0.75, and 1), were prepared using a modified polymeric precursor method, characterized using several techniques, and evaluated at 800 °C with a sub-stoichiometric molar feed composition of CH4/CO2/H2O/O2 = 1/0.33/0.33/0.08. The catalyst with x = 0.5 showed the best performance, which is attributed to its optimum properties of nickel particle size, metal-support interactions, and basicity. A stability test was performed with this catalyst using a molar feed composition of CH4/CO2/H2O/O2 = 1/0.33/0.67/0.08, previously optimized to obtain a synthesis gas with a H2/CO ≈ 2 molar ratio for 100 h, and compared with a commercial steam reforming catalyst. The catalyst with x = 0.5 exhibited higher CH4 and CO2 conversions, a lower amount of carbon deposited, and a lower degree of nickel particle sintering.