Insights into the selective reduction of NO over Al2O3-supported Pt, Rh, and Pd catalysts

Abstract

In this study, we elucidate the formation mechanism of by-products especially N₂O during NO purification using H₂ as a reductant on alumina-supported Pt, Pd, and Rh catalysts by looking into the catalytic reaction dynamics and NO adsorption/desorption properties, as well as chemical state change of catalysts, with assistance of advanced characterization techniques including the NO pulse method, in situ temperature/atmosphere controlled FT-IR and XPS analysis. It was found that the surface NO adsorption/desorption properties and surface oxygen species of PGM catalysts result in significantly distinguished by-product formation behavior. Lower formation of N₂O and NH₃ was confirmed on the Rh/Al₂O₃ catalyst rather than the Pd and Pt cases, whose phenomenon is attributed to the high stability of the Rh–NO⁺ chemical bond formed. Additionally, Rh–O bonding tends to be more stable than that of Pt and Pd, also contributing to the suppression of NO dissociation and subsequent by-product formation. These findings provide valuable insights into the design and development of advanced catalysts aimed at minimizing the emission of greenhouse gases such as N₂O.