Promoting Effect of Cerium Oxide on the Catalytic Performance of Yttrium Oxide for Oxidative Coupling of Methane

摘要

The promoting effect of CeO2 on the catalytic performance of Y2O3, which is moderately active catalyst, for the oxidative coupling of methane (OCM) reaction was investigated. The addition of CeO2 into Y2O3 by coprecipitation method caused a significant increase in not only CH4 conversion but also C2 (C2H6/C2H4) selectivity in the OCM reaction. C2 yield at 750 °C was increased from 5.6% on Y2O3 to 10.2% on 3 mol% CeO2/Y₂O₃. Further increase in the CeO₂ loading caused an increase in non-selective oxidation of CH₄ to CO₂. A good correlation between the catalytic activity for the OCM reaction and the amount of H₂ consumption for the reduction of surface/subsurface oxygen species in the H₂-TPR profile was observed, suggesting the possibility that highly dispersed CeO₂ particles act as catalytically active sites in the OCM reaction. The ¹⁶O/¹⁸O isotopic exchange reaction suggested that the beneficial role of CeO₂ in the OCM reaction is to promote the formation of active oxygen species via the simple hetero-exchange mechanism, resulting in the promotion of CH₄ activation.