Peculiarities of oxidative coupling of methane in redox cyclic mode over Ag-La2O3/SiO2 catalysts

Properties of Ag-La2O3/SiO2 catalysts in oxidative coupling of methane (OCM) carried out in redox cyclic mode were studied. Methane and air were injected as separate and alternating pulses, and the oxidative conversion of methane proceeded due to participation of mobile lattice oxygen of the catalysts. It was found that joint action of Ag and La2O3 in OCM could give considerable synergetic effect. Such catalysts as 3%Ag-10%La2O3/SiO2 and 6%Ag-10%La2O3/SiO2 exhibited high efficiency in the OCM reaction performed in the redox cyclic mode. In the case of 3%Ag-10%La2O3/SiO2, the yield of C-2 hydrocarbons reached about 30% at C-2 selectivity close to 60%. Active sites which were responsible for OCM reaction were generated during reduction of silver by the injected methane. OCM selectivity increased remarkably if a small amount of hydrogen was injected over the catalyst before the methane pulse. (C) 2010 Elsevier B.V. All rights reserved.