Binary oxides of Y2O3CaO were evaluated as catalysts in the oxidative coupling of methane to C2+(sum of C2H6, C2H4, C3H8, and C3H6) hydrocarbons. Passing a mixture of CH4/O2and He gases (at 6, 3 and 31 ml/min respectively) in a fixed-bed flow reactor 13% and 7.5% of C2+yields were achieved at 750°C and 650°C, respectively, over 0.5 g of 10 mol-% Y2O3CaO catalyst prepared by calcining a coprecipitate of their oxalates at 800°C. The C2+yields on 10 mol-% Y2O3CaO, prepared by physical mixing, were lower than those on the coprecipitated catalyst. With increasing Y2O3content in the coprecipitated catalyst, the C2+selectivity at 700°C was significantly enhanced even at ca. 3 mol-%, whereas at 600°C such a change was not observed. A similar dependence on the Y2O3content was found in the way both surface areas and basicities decreased. Those changes were attributed to the formation of a solid solution accompanying the production of interstitial oxygen ions. Electron-spin resonance (ESR) studies indicated that the ion is a superoxide ion which is responsible for the generation of methyl radical from methane. At low reaction temperatures, 700°C, it was found that a lattice distortion of Y2O3in the binary oxides also affected the C2+selectivity. © 1990.
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