CATALYTIC PROPERTIES OF COPPER-OXIDE SUPPORTED ON ZINC ALUMINATE IN METHANE COMBUSTION

Copper oxide was deposited on a zinc aluminate prepared from high specific area alumina and zinc nitrate. The activity of the solid obtained has been measured in the catalytic combustion of methane before and after an aging test performed at 1340 K. The environment of the copper species was followed by UV-VIS reflectance spectroscopy whereas the state of copper was deduced from temperature-programmed reduction experiments. By comparison with a series of CuO/Al2O3 catalysts, the CuO/ZnAl2O4 sample is slightly less active in the complete oxidation of methane. This decrease in catalytic activity is connected with the presence of bulk CuO particles on the zinc aluminate support instead of isolated copper ions in the case of the alumina carrier. Slight deactivation was observed after the aging test at 1340 K whereas the CuO/Al2O3 system was strongly deactivated under the same conditions. Spectroscopic and TPR experiments have shown that the copper oxide phase was preserved in the case of the zinc aluminate supported copper oxide. The formation of the copper aluminate phase at the origin of the dramatic loss in activity of the aged CuO/Al2O3 catalyst barely occurs when copper oxide is supported on zinc aluminate.