Oxidative Coupling of Methane on Strontium Titanate with Oxide Ion Defects
Xiao-Hong LI, Keiichi TOMISHIGE, Kaoru FUJIMOTO
Perovskite type strontium titanate, in which Ti4+ion was partly substituted by Mg2+ and the oxide ion defects were formed, was prepared by doping Mg0 to SrCO3-Ti02 mixture at 1473K. We found that this oxide was active catalyst for the oxidative coupling of methane (0CM) and its activity increased with increasing the amountof oxide ion defects and reached the maximum level at the substitution ratio of 40-60%. The reaction of methane with SrTi0.4Mg0.6O3-δ and SrTiO3 in the absence of oxygen gave C2 hydrocarbons and COx. The selectivity at the initial stage agreed with that of the steady-state catalytic reaction of the oxidative coupling of methane.
From these results and O2 TPD result which has been reported, it is suggested that the addition of Mg2+modify the reactivity of the lattice oxide ion and the lattice oxide ion, which desorbed in the temperature range 873 K-1273 K on TPD measurement, is re-sponsible for the selective oxidative coupling of methane.