(98g) Ceria Enhancement of Sinter-Resistant Platinum-Based Catalysts for Emission Control Applications

Platinum group metals (PGM) are widely used for exhaust emission abatement. Sintering that occurs during the oxidative, high temperature conditions of emission control decreases noble metal utilization efficiency. As a result, catalytic converters rely on excessive catalysts loadings, which account for 51% of the global demand for PGM. Efficient use of scarce noble metals requires sinter-resistant catalysts. We recently developed a nanocasting method for encapsulating PGM nanoparticles (NPs) inside porous Al₂O₃ using a templating procedure with a polymer framework. The resulting catalyst, termed Pt@Al₂O₃, demonstrated stability against sintering at 800°C under 3% O₂ and 5% H₂O, evidenced by its sustained propene combustion activity and the preservation of Pt particle size (4 nm). Encouraged by the propene combustion activity, we further simulate realistic exhaust stream conditions by targeting relevant oxidation reactions of Pt@Al₂O₃ with carbon monoxide (CO) and propane. Ceria (CeO₂) is known to enhance CO oxidation activity of PGM particles through oxygen donation from the support. However, ceria is prone to restructure under high temperature aging conditions and loses porosity. Here, we incorporate CeO₂ into the nanocasting approach to generate Pt@CeO₂/Al₂O₃ catalysts. Through a suite of characterization techniques, we track the morphological changes of Pt and CeO₂ encapsulated in an Al₂O₃ framework as a function of aging. Using reaction kinetics, we study the site requirements of propane, propene, and CO combustion independently and mixed. Taken together, we can enhance the reactivity of Pt for a wider range of emission components while maintaining catalyst stability during high-temperature aging conditions.