La1-xCaxNiO3 perovskite oxides:: Characterization and catalytic reactivity in dry reforming of methane

Perovskite-type oxides such as La1-xCaxNiO3 (x = 0.0, 0.05, 0.1, 0.3, 0.5 and 0.8) have been prepared from citrate precursors and characterized by XRD, TPR, TG-H-2 and XPS. Catalytic experiments in the reforming of CH4 with CO2 have been carried out in a tubular reactor at 750 degrees C and atmospheric pressure. After the catalytic tests the catalysts were studied by TPO and SEM. Partial substitution of La by Ca was performed to stabilize Ni particles and to prevent carbon deposition. The XRD profiles showed that the perovskite structure is the only compound identified within the 0 <= x <= 0.05 range, whereas for x >= 0.1 compounds such as spinel-type La2NiO4, NiO and CaO were observed in addition to the perovskite oxide. On the other hand, segregation of NiO, even in the unsubstituted perovskite (x = 0.0), was confirmed by TPR and XPS. The catalytic tests showed that the replacement of La by Ca, which has a lower ionic radius, favored a higher activity and stronger resistance to carbon deposition. However, this coking resistance depended on the Ca-loading and the catalysts with x = 0.05 and x = 0.8 were the most stable against deactivation.