Mn2O3-Na2WO4 doping of CexZr1-xO2 enables increased activity and selectivity for low temperature oxidative coupling of methane

Abstract

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 CexZr1-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 Ce0.15Zr0.85O2 can generate more O2– species thereby leading to a markedly improved activity and selectivity at much lowered reaction temperature.