Mn₂O₃-Na₂WO₄ doping of Ce_xZr_1-xO₂ enables increased activity and selectivity for low temperature oxidative coupling of methane

Ethylene in principle can be obtained via oxidative coupling of methane (OCM), but it is urgently calling for a low-temperature active and selective catalyst. To accomplish this goal, the Ce_xZr_1-xO₂ solid solutions with varied Ce/Zr molar ratio were modified with Mn₂O₃-Na₂WO₄ to fabricate OCM catalysts. The effects of Ce/Zr ratio and Mn₂O₃-Na₂WO₄ doping were investigated on the catalyst reactivity for the OCM, showing that the reaction light-off temperature, activity and selectivity are subject to the Ce/Zr molar ratio and Mn₂O₃-Na₂WO₄ doping. The promising catalyst with Ce/Zr molar ratio of 0.15/0.85 achieves 25% CH₄ conversion with 67% selectivity to C₂-C₃ at 660 °C and is stable for at least 100 h. The catalysts were systematically studied by CH₄-TPSR, O₂-TPO/-TPD, CH₄-pulse, in-situ FT-IR, EPR and XPS, showing that the Mn₂O₃-Na₂WO₄ doped Ce_0.15Zr_0.85O₂ can generate more O₂^– species thereby leading to a markedly improved activity and selectivity at much lowered reaction temperature.