Catalytic Activity of C 3 H 8 over Fresh and Aged Pd/Al 2 O 3 Close-Coupled Catalysts

Abstract The Pd/Al 2 O 3 close-coupled catalysts supported on modified alumina were prepared by an impregnation method, and then characterized by H 2 -temperature programmed reduction (H 2 -TPR), CO chemisorption, and X-ray photoelectron spectroscopy (XPS). Both total catalytic activity and single reactions in related to C 3 H 8 conversion were tested in simulated exhaust gas. The results show that the amount of active PdO x decreases and negative metallic Pd 0 appears during aging treatment. The light-off temperature ( T 50 ) and complete conversion temperature ( T 90 ) increase by 76 °C and 64 °C, respectively. After aging treatment, signifying that the low-temperature activity decreases more obviously than high temperature property. The results of comparison among single reactions indicate that the light-off activity of reactions which occur in atmosphere with the participation of NO but without H 2 O injection decreases dramatically after the aging treatment. The inhibitive effect of NO on light-off activity and the positive effect of H 2 O on high temperature property become obvious during the aging treatment.