Ammonia and toluene oxidation: Mutual activating effect of copper and cerium on catalytic efficiency

Abstract

Copper and cerium containing hydrotalcite-like precursors Cux-Cey-Mg-Al were synthesized by mutual coprecipitation followed by calcination at 800 degrees C. The obtained mixed metal oxides were studied as catalysts for selective ammonia oxidation (NH 3 -SCO) and toluene combustion. Various techniques, such as temperatureprogrammed reduction with hydrogen, temperature -programmed desorption of toluene, scanning electron microscopy and reactive frontal chromatography were used to characterize the catalysts. Series 800-Cux-Ce2.5 showed the highest catalytic efficiency in both reactions, allowing complete NH 3 and C 7 H 8 conversion below 350 degrees C and 500 degrees C, respectively. CeO 2 crystallites (12-18 nm), as well as dispersed CuO oxide forms were found in the most active samples. Both phases affect pollutants conversion, however, for ammonia oxidation the occurrence of Cu 2+ is essential, while for toluene oxidation, the formation of Ce 4+ is sufficient. Over the most active sample (800-Cu5-Ce2.5) the complete conversion in mutual oxidation of NH 3 and toluene was achieved below 450 degrees C.