Oxidative coupling of methane on SrTi1-xMgxO2-delta catalysts: Formation of oxide ion defects and the effect of oxidizing reagents on catalytic activity and selectivity

We discovered that oxygen species adsorbed on SrTi1-xMgxO3-delta catalysts prepared by the addition of Mg2+ ions instead of Ti4+ ions on an SrTiO3 catalyst reacted with methane to form ethane selectively at temperatures as low as 700 K. At this temperature the catalytic reaction did not proceeded under atmospheric pressure because the oxygen adsorption site was poisoned by H2O which was a reaction product. We found that highly selective and catalytic C-2 hydrocarbons were formed on these catalysts by CH4-H2O and CH4-CO2 reactions similar to a CH4-O-2 reaction It is suggested that H2O and CO2 were effective oxidants for the oxidative coupling of methane. In the cases of CH4-O-2 and CH4-H2O reactions, SrTi0.4Mg0.6O3-delta showed superior catalytic performance compared to SrTiO3 whereas the reverse was tone for a CH4-CO2 reaction The interaction between oxidizing reagents and oxide ion defects seems to play an important role in the catalytic activity and selectivity of the oxidative coupling of methane.