Abstract
The bimetallic Pd-Rh three-way catalysts were prepared by an incipient wetness impregnation of γ-Al2O3 with a joint solution of [Pd(NH3)4](NO3)2 and Na3 [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 °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.
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