Au/xCeO2/Al2O3 catalysts for VOC elimination: oxidation of 2-propanol

Abstract

2-Propanol oxidation (1 mol% in air) was investigated over 1%Au/CeO2, 1%Au/Al2O3 and 1%Au/xCeO2/Al2O3 (x = 1.5, 3, 5 and 10 wt%) catalysts and the corresponding pure supports. The effects of the catalyst activation procedure (calcination or reduction), cerium oxide morphology and loading, the presence/absence of O2 in the feed, and stability of activity were studied. The nature of the support strongly influences the 2-propanol oxidation pathway, and one can distinguish three reaction temperature ranges: low (50–150 °C), intermediate (175–250 °C) and high (>300 °C). In the low temperature range, only acetone is formed whatever the nature of the support. On Au/Al2O3 and Au/xCeO2/Al2O3 catalysts propene becomes the main reaction product by increasing the temperature, followed by CO2 formation at higher temperature. The acidic character of Al2O3 and CeO2/Al2O3 promotes the propene formation whereas the basic one of CeO2 favors the formation of acetone, and the gold catalysts also present an acidic–basic behavior, which depends largely on the reaction temperature. Replacing air with He during the catalytic run over Au/Al2O3 and Au/CeO2 provides evidence of how O2 is activated by Au, revealing, as expected, that dehydrogenation to form acetone and total oxidation to CO2 require both O2 and Au as the catalyst, whereas dehydration to form propene does not require O2. For both calcined and reduced catalysts, the catalytic activity towards total oxidation varies in the order: Au/CeO2 > Au/xCeO2/Al2O3 > Au/Al2O3.