Cu-Mg-Al hydrotalcite-like materials as precursors of effective catalysts for selective oxidation of ammonia to dinitrogen — The influence of Mg/Al ratio and calcination temperature

Abstract

Hydrotalcite originated Cu-Mg-Al mixed metal oxides were studied as catalysts for selective oxidation of ammonia to dinitrogen. Cu-Mg-Al hydrotalcite-like materials with copper content of 5mol% and various molar Mg/Al ratios were synthetized by coprecipitation method and then calcined at 600, 700 and 800°C. It was shown that both Mg/Al ratio as well as calcination temperature are very important synthesis parameters determining selectivity of the studied catalysts in ammonia oxidation process. The catalysts with lower Mg/Al ratio, so higher Al content, were more selective to dinitrogen. Moreover, it was shown that an increase in calcination temperature also resulted in the catalysts with a significantly improved selectivity to dinitrogen. These interesting effects were related to the formation of the Cu-containing spinel phases, which possibly are responsible for high selectivity to dinitrogen in the high temperature range.