Al2O3-supported transition-metal oxide catalysts for catalytic incineration of toluene.

The catalytic incineration of toluene over gamma-Al2O3-supported transition-metal oxide catalysts in the temperature range of 200-380 degrees C was investigated employing a fixed bed flow reactor. CuO/gamma-Al2O3 was found to be the most active of seven catalysts tested. Using this catalyst with different wt% Cu in the incineration of toluene, we found that the optimal Cu content was 5 wt%. X-ray diffraction, BET surface area and hydrogen-temperature-programmed reduction showed that it was mainly the formation of large CuO crystals that caused declines in catalyst activity at Cu content above 5 wt%. Addition of water vapor or CO2 inhibited catalyst activity, but this effect was reversible. Although coexistence of toluene and n-hexane resulted in a reduction in n-hexane conversion, the impact on toluene oxidation was only negligible. Temperature-programmed desorption revealed that this differential effect was due to more competitive adsorption of toluene onto active sites of the catalyst.