Silanol-Stabilized\nAtomically Dispersed Pt<sup>δ+</sup>-O<sub><i>x</i></sub>‑Sn Active Sites in Protozeolite\nfor Propane Dehydrogenation

Crystalline zeolites have been proven to be excellent\nsupports\nfor confining subnanometric metal catalysts to boost the propane dehydrogenation\n(PDH) reaction. However, the introduced metallic species may suffer\nfrom severe sintering and limited stability during the catalytic process,\nespecially when utilizing an industrial impregnation method for metal\nincorporation. In this study, we developed a new type of support based\non amorphous protozeolite (PZ), taking advantage of its adjustable\nsilanol chemistry and zeolitic microporous characteristic for stabilizing\natomically dispersed PtSn catalyst via a simple, cost-effective coimpregnation\nprocess. The combination of X-ray absorption spectroscopy, X-ray photoelectron\nspectroscopy, in situ diffuse reflectance infrared Fourier transform\nspectroscopy under CO atmosphere, and density functional theory calculations\nconfirmed the formation of highly dispersed active Pt<sup>δ+</sup>-O<sub><i>x</i></sub>-Sn species in PtSn/PZ. The PtSn/PZ\ncatalyst exhibited a high propane conversion of 45.4% and a high propylene\nselectivity of 99% (WHSV= 3.6 h<sup>–1</sup>, 550 °C),\nwith a high apparent rate coefficient of 565 mol<sub>C<sub>3</sub>H<sub>6</sub></sub>·g<sub>Pt</sub><sup>–1</sup>·h<sup>–1</sup>·bar<sup>–1</sup> at a high WHSV of 108 h<sup>–1</sup>, presenting\na top-level performance among the state-of-the-art Pt-based catalysts\nprepared by in situ synthesis and impregnation methods. The silanol\ndensity determined the chemical state of PtSn species, showing a change\nfrom atomically dispersed Pt<sup>δ+</sup>-O<sub><i>x</i></sub>-Sn sites to PtSn alloy with decreasing silanol density of\nsupports. This work provides a general strategy using silanol-rich\namorphous protozeolite as support for stabilizing various metal catalysts\nby the simple impregnation method and also offers an effective way\nfor fine tailoring the chemical state of metallic species via a silanol-engineered\napproach.