Unraveling the Unique Behavior of Atomically Dispersed Pt on Zeolite Fe-DeAlBEA for Catalyzing Propane Dehydrogenation with Cofed Hydrogen
Afnan Alghannam, Alexander J. Pattison, Sonali Das, Chaochao Dun, Peter Ercius, Jeffrey J. Urban, Bruce C. Gates, Alexis T. Bell
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 H 2 . 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 H 2 partial pressure, whereas metallic Pt clusters, formed at high Pt loadings, catalyze the reaction with a slightly negative dependence on H 2 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.