Highly Active and Durable Rh–Mo-Based Catalyst for the NO–CO–C3H6–O2 Reaction Prepared by Using Hybrid Clustering

Abstract

We developed a method for preparing catalysts by using hybrid clustering to form a high density of metal/oxide interfacial active sites. A Rh–Mo hybrid clustering catalyst was prepared by using a hybrid cluster, [(RhCp*)₄Mo₄O₁₆] (Cp* = η⁵-C₅Me₅), as the precursor. The activities of the Rh–Mo catalysts toward the NO–CO–C₃H₆–O₂ reaction depended on the mixing method (hybrid clustering > coimpregnation ≈ pristine Rh). The hybrid clustering catalyst also exhibited high durability against thermal aging at 1273 K in air. The activity and durability were attributed to the formation of a high-density of Rh/MoO_x interfacial sites. The NO reduction mechanism on the hybrid clustering catalyst was different from that on typical Rh catalysts, where the key step is the N–O cleavage of adsorbed NO. The reducibility of the Rh/MoO_x interfacial sites contributed to the partial oxidation of C₃H₆ to form acetate species, which reacted with NO+O₂ to form N₂ via the adsorbed NCO species. The formation of reduced Rh on Rh₄Mo₄/Al₂O₃ was not as essential as that on typical Rh catalysts; this explained the improvement in durability.