Dual functional adsorbent/catalyst of nano-gold/metal oxides supported on carbon grain for low-temperature removal of toluene in the presence of water vapor

Abstract

Low-temperature removal of the volatile organic compounds especially aromatic compounds such as toluene in highly humid condition is currently a great challenge. In order to minimize the mass transfer limitation at low temperature, various dual functional adsorbent/catalyst consisting nano-gold/metal oxides supported on carbon grain or granular activated carbon (GAC) have been prepared using a simple and practically feasible method. The surface morphology and structure of these ready-to-practically use materials were characterized to confirm the presence of nano-Au on the GAC as well as the properties of the dual functional adsorbent/catalyst. The results of catalytic performance revealed that the metal oxides (CeO2 and Fe2O3) played an important role in the formation of nano-Au which was the catalytic active site for toluene oxidation as well as weakening metal-O bonds. At 75 °C, the nano-Au/Fe2O3/GAC and nano-Au/CeO2/GAC could remove about 80% of toluene, which was 20% higher than the toluene removal efficiency obtained in the case of the Au/GAC. Importantly, under 40% relative humidity condition at 75 °C, the nano-Au/Fe2O3/GAC dual functional adsorbent/catalyst still maintained the high toluene removal efficiency at 76%. The Mars–van Krevelen (MVK) reaction mechanism for toluene oxidation is possible to explain the dual functional activity of the nano-Au/metal oxides supported on the carbon grain in this study.