Structure-sensitivity of alumina supported palladium catalysts for N2O decomposition

The catalytic activity of Pd/γAl2O3 for N2O decomposition was found to be highly dependent on the preparation methodology and the number of reaction cycles. Chloride species on the surface of a 2.6 wt. % Pd-Al2O3 catalyst prepared by wet impregnation were identified as inhibiting the activity. Multiple reaction cycles were shown to remove these species, and a subsequent increase in activity was observed; 10.3 molN2O h−1 kgcat−1 in the first use, increased to 28.7 molN2O h−1 kgcat−1 on the fourth use both at 550 °C. Additionally, removal of physisorbed water from the support prior to metal deposition increased the thermal stability of Pd nanoparticles and increased the catalyst activity. Catalysts were subsequently prepared using a deposition technique with an increased concentration of Cl- ions resulted in increased Pd-Cl species in the final catalyst and the catalytic activity was consequently increased due to the improved control of Pd particle size