A decrease in NiO-MgO phase through its solid solution equilibrium with tetragonal (La1-z Srz)2 Ni1-y Mgy O4-δ: Effect on catalytic partial oxidation of methane

Abstract

Calcination of an oxide mixture consisting of 0.4 La2O 3, 0.2 SrCO3, (1 - x) NiO, and x MgO at 800 °C results in an equilibrium between tetragonal (La1-z Srz) 2 Ni1-y Mgy O4-δ phase and NiO-MgO phase. Forming rock-salt NiO-MgO facilitates the NiO to join the tetragonal phase. The size of the NiO-MgO phase in the resulting composite is reduced with the increase in MgO (the x value). The composite thus obtained is used to catalyze partial oxidation of methane, and the maximum methane conversion of ca. 93 is achieved when x = 0.2. A further rise in x value results in a monotonic decrease in the methane conversion. X-ray diffraction, electron microscopy, and chemosorption all confirm a decrease in both size and amount of the supported Ni 0 clusters with the increase in MgO dosage. The reduction in size promotes the dispersion of Ni 0 sites and gives rise to both high activity and strong coking resistance. © 2012 Xiong Yin et al.