Effect of metal ratio in alumina-supported Pd-Rh nanoalloys on its performance in three way catalysis

The bimetallic Pd-Rh three-way catalysts were prepared by an incipient wetness impregnation of gamma-Al2O3 with a joint solution of [Pd(NH3)(4)](NO3)(2) and Na-3 [Rh(NO2)(6)]. The ratio of the metals was varied by changing the ratio of the salt-precursors. The samples with Pd:Rh ratio of 3:2, 7:3 and 4:1 were compared in simultaneous oxidation of carbon monoxide, propane, propylene, and reduction of nitrogen monoxide at a lambda factor of 1.003 and 0.95. Stability tests were performed in a prompt thermal aging regime (consecutive heating-cooling cycles with a final temperature of 320, 600 and 800 degrees C). The samples were characterized by UV-vis and luminescence spectroscopies, and by testing reaction of ethane hydrogenolysis. It was found that the sample with Pd: Rh ratio of 3:2 is characterized with strong palladium-rhodium interaction, which makes this catalyst more stable at high temperature if compare with other alloyed Pd-Rh samples. Moreover, the mechanism of the three-way catalytic process over Pd:Rh (3:2) sample differs from other cases and involves a larger contribution of reactions with nitrogen oxide. (C) 2018 Elsevier B.V. All rights reserved.