Unraveling the Unique Behavior of Atomically Dispersed Pt on Zeolite Fe-DeAlBEA for Catalyzing Propane Dehydrogenation with Cofed Hydrogen

Abstract

Propene, used on a large scale to manufacture polypropylene and several commodity chemicals, is increasingly produced by catalytic propane dehydrogenation (PDH). Atomically dispersed Pt has emerged as a promising candidate catalyst for PDH; however, stabilizing atomically dispersed Pt at high temperatures is challenging. Here, we demonstrate the use of dealuminated zeolite beta with a high Fe content as a host for stabilizing isolated Pt, which is anchored strongly to the zeolite support by Pt–Fe bonds. The isolated Pt–Fe sites exhibit promising PDH performance, including a high apparent forward rate coefficient for propene formation (404.8–26.4 mol propene/mol Pt·bar·s) and a high selectivity (≥96%) at 823 K in the presence of H₂. Kinetics data characterizing the rate of PDH with a range of Pt loadings show that atomically dispersed Pt catalyzes propene formation at rates independent of H₂ partial pressure, whereas metallic Pt clusters, formed at high Pt loadings, catalyze the reaction with a slightly negative dependence on H₂ partial pressure. The shift in Pt speciation with Pt loading, confirmed by infrared spectroscopy of adsorbed CO, X-ray absorption spectroscopy, and high-angle angular dark field scanning transmission electron microscopy, suggests that the observed change in kinetics with Pt dispersion is a consequence of a change in the reaction mechanism.