STRUCTURE AND REACTIVITY OF ALKALI-DOPED CALCIUM-OXIDE CATALYSTS FOR OXIDATIVE COUPLING OF METHANE

The effects of the promoter content and the partial pressure of methan e and oxygen on the C2+ hydrocarbon formation, carbon oxides formation and methane conversion in the oxidative coupling of methane over alka li-promoted calcium oxide catalysts were studied in a fixed bed cataly tic reactor. It was found that both methane conversion and C2, hydroca rbon yield increase substantially with alkali doping up to alkali cont ents around 2 % (molar basis), and then levels off or even decreases s lightly. At times-on-stream below 20 min both selectivity to carbon ox ides (CO(x)) and carbon balances were rather low. In agreement with th ermogravimetric and photoelectron spectroscopic data, this was interpr eted in terms of catalyst carbonation by the carbon dioxide produced i n the reaction during the initial stages of the catalytic run.