Structure and reactivity of alkali-doped calcium oxide catalysts for oxidative coupling of methane

Abstract

The effects of the promoter content and the partial pressure of methane and oxygen on the C2+ hydrocarbon formation, carbon oxides formation and methane conversion in the oxidative coupling of methane over alkali-promoted calcium oxide catalysts were studied in a fixed bed catalytic reactor. It was found that both methane conversion and C2+ hydrocarbon yield increase substantially with alkali doping up to alkali contents around 2% (molar basis), and then levels off or even decreases slightly. At times-on-stream below 20 min both selectivity to carbon oxides (COX) and carbon balances were rather low. In agreement with thermogravimetric and photoelectron spectroscopic data, this was interpreted in terms of catalyst carbonation by the carbon dioxide produced in the reaction during the initial stages of the catalytic run.