Toluene destruction over nanometric palladium supported ZSM-5 catalysts: influences of support acidity and operation condition

The effects of catalyst physicochemical property and operation condition on toluene destruction over Pd/Z-x (Z: ZSM-5; x: n _Si/Al) were extensively studied. The support acidity has important impact on active phase dispersion and reaction product desorption. Pd/Z-25 shows the highest catalytic activity with toluene complete conversion at 220 °C, which is about 60 °C lower than that of Pd/Z-300. Both Pd loading and space velocity are key experimental factors determining toluene oxidation activity. The water vapor has a significant negative effect on the oxidation reaction, especially for the catalyst with higher Al content. The activity of the used Pd/Z-25 could not regain its initial level after removal of water vapor due to the formation of coke. Pd⁰ and Pd²⁺ species have a synergetic effect on toluene oxidation, and the catalytic activity is primarily correlated to the support acidity, the active phase dispersion, and the CO₂ desorption capability.