Study of nitrous oxide utilization for syngas production via partial oxidation of methane using Ni-doped perovskite catalysts

Four different materials-pure NiO, pure LSCF (La0.3Sr0.7Co0.7Fe0.3O3-delta), 10% Ni/LSCF, and 20% Ni/LSCF-were studied. The Ni/LSCF catalysts demonstrated superior catalytic performance for both N2O decomposition and the partial oxidation of methane (POM) compared to pure NiO and pure LSCF. This enhancement is attributed to an increase in oxygen vacancies and improved oxygen mobility within the catalyst, as evidenced by O2-TPD analysis. During N2O decomposition, both LSCF and 10% Ni/LSCF achieved complete N2O conversion at 800 degrees C, whereas pure NiO provided 81.7% at the same temperature. However, 10% Ni/LSCF is more active at lower temperatures, as evidenced by its T50 value of 536 degrees C, compared to 546 degrees C for the unmodified LSCF. For the POM reaction using N2O as an oxidant, 10% Ni/LSCF achieved 70.9% CH4 conversion, 96.6% CO selectivity, and 97.4% H2 selectivity at 600 degrees C. In contrast, both pure LSCF and 20% Ni/LSCF catalysts exhibited significantly lower efficiency, with approximately 20% CH4 conversion and less than 5% syngas selectivity. The enhanced performance of the 10% Ni/LSCF compared to the 20% Ni/LSCF is likely attributed to its smaller Ni crystallite size (23.7 nm vs. 32.3 nm) and the lower temperature required for reducing Ni2+ to the active Ni0 species (480 degrees C vs. 500 degrees C). Kinetic analysis of the POM reaction using N2O over the 10% Ni/LSCF catalyst revealed a second-order reaction with respect to CH4 and a zero-order reaction with respect to N2O, with an apparent activation energy of 71.8 kJ mol-1.