Catalytic combustion of methane over cobalt-magnesium oxide solid solution catalysts

A series of cobalt-magnesium oxide solid solution catalysts (CoMgO) have been prepared using urea combustion methods, and characterised by X-ray diffraction (XRD) and laser Raman (LR). The catalytic activities for methane combustion have been tested in a continuous-flow microreactor. The Co content has a significant effect on the activity of the cobalt-magnesium oxide solid solution catalysts. The catalysts containing 5 and 10% Co have the lowest light-off temperature in methane combustion. In the preparation of cobalt-magnesium oxide solid solution catalysts, higher urea to metal ratio favors the formation of the catalysts with smaller crystal particles and leads to a better catalytic performance for methane combustion. Addition of lanthanum nitrate to the solution of Co and Mg nitrate depressed the formation of the cobalt-magnesium oxide solid solution and decreased the activity of the catalysts for methane combustion. The cobalt-magnesium oxide solid solution catalysts are very stable when the calcination or reaction temperature is no more than 900 degreesC. However, the catalytic activity decreases rapidly after high temperature (> 1000 degreesC) calcination, possibly due to sintering of the catalyst and thus decrease of the surface area.