Oxidative coupling of methane over Ba-doped Y2O3 catalyst—Similarity with active site for direct decomposition of NO

Abstract

A similarity of catalytically active sites for oxidative coupling of methane (OCM) and NO decomposition was investigated. Y2O3 prepared by different methods showed the activity for both reactions. However, no good correlation between the C2 (C2H6 and C2H4) yield for the OCM reaction and the NO decomposition activity was observed. Since the disagreement of the catalytic activity for both reactions was suspected to be due to the non-uniform surface morphological properties of Y2O3, detail experiments were performed for Ba-doped Y2O3 catalysts. It was noteworthy that the addition of Ba into Y2O3 prepared by precipitation method caused a significant increase in not only the C2 yield for the OCM reaction but also the NO decomposition activity. The order of the C2 yield for the OCM reaction over Ba/Y2O3 with different Ba loading was in good agreement with that for the NO decomposition, suggesting the similarity of the active sites for the OCM and NO decomposition reactions. XRD, FT-IR spectroscopy following methanol adsorption and 16O/18O isotopic exchange reaction revealed that the oxygen-deficient Y3+ sites interacting strongly with Ba play a beneficial role in O2 activation, leading to the activation of CH4 and NO molecules to form intermediate in the OCM and NO decomposition reactions.