Design of Ni-substituted La-2(CeZrNi)(2)O-7 Pyrochlore Catalysts for Methane Dry Reforming

Ni-based catalysts for dry reforming of methane (DRM) are prone to suffer from deactivation caused by carbon deposition and sintering. Pyrochlore (typically A(2)B(2)O(7)) is a thermostable material with substantial redox capacity, which makes it suitable as a support for Ni-based DRM catalysts. Here we demonstrated that by adjusting the Zr/Ce ratio in the B-site of the La-2(CeZrNi)(2)O-7 (10 wt.% Ni loading), its structural order could be significantly altered. With decreasing Zr/Ce ratio, the structure of the catalysts became less ordered with a phase transformation from pyrochlore (La2Zr2O7) to defective fluorite (La2Ce2O7). Meanwhile, a second phase La2NiZrO6/LaNiO3 other than pyrochlore was formed for each sample. By tuning the structure, samples presented different properties and XPS results illustrated that the compositions of the surface oxygen species of samples were significantly different. Catalysts possessing more oxygen vacancies displayed evidently enhanced coke resistance. Among all five catalysts, LNZ3C1 exhibited the highest activity, stability and carbon deposition resistance, which could be attributed to the most oxygen vacancies, the strongest nickel-carrier interaction, and the best particle size distribution of it.