Catalytic performance and QXAFS analysis of Ni catalysts modified with Pd for oxidative steam reforming of methane

Pd–Ni bimetallic catalysts prepared by co-impregnation and sequential impregnation methods were compared in the catalytic performance in oxidative steam reforming of methane. The sequential impregnation was more effective to the suppression of hot spot formation. According to the structural analysis by in situ quick-scanning X-ray absorption fine structure (QXAFS) during the temperature programmed reduction, the sequential impregnation method gave the bimetallic particles with higher Pd surface composition because of the low possibility of the Pd–Ni bond formation. Higher surface composition of Pd with higher reducibility than Ni is connected to the enhancement of the catalyst reducibility and the suppression of the hot spot formation

Promoting effect of MgO addition to Pt/Ni/CeO2/Al2O3 in the steam gasification of biomass

Pt/Ni/CeO2/Al2O3 catalyst showed the high performance in the steam gasification of cedar wood at the initial stage, however, the catalyst was deactivated within 2 h. According to the catalyst characterization by means of XRD and Ni K-edge EXAFS, it is found that aggregation of Ni metal particles causes the deactivation. In contrast, the Pt/Ni/CeO2/MgO/Al2O3 showed the high catalytic activity and stability. The addition of MgO to Pt/Ni/CeO2/Al2O3 decreased the reduction degree of Ni, but increased the dispersion of the Ni metal particles. As a result, the activity of Pt/Ni/CeO2/MgO/Al2O3 was comparable to that of Pt/Ni/CeO2/Al2O3. The Pt/Ni/CeO2/MgO/Al2O3 had high resistance to the aggregation, which can be related to high stability. Another important point is that the aggregated Ni particles on the Pt/Ni/CeO2/MgO/Al2O3 became re-dispersed by the catalyst regeneration (oxidation and reduction). The re-dispersion can proceed via the formation of the NiO–MgO solid solution by oxidation and the reduction of the NiO–MgO from the results of XRD and Ni K-edge EXAFS