Resolving Complex K–Pt–Sn Interactions in PtSn@K-MFI Catalysts for Alkane Dehydrogenation
Adrián Martínez Gómez-Aldaraví, Reisel Millán, Isabel Millet, Aroa Alós, Alejandro Vidal‐Moya, Randall J. Meyer, Cristina Martı́nez, Avelino Corma, Mercedes Boronat, Pedro Serna, Manuel Moliner
Abstract
High Resolution Image Download MS PowerPoint Slide K and Sn contents were rationalized during the synthesis of PtSn@K-MFI to maximize metal dispersion and stability along the MFI crystallites. Experimental results and theoretical calculations reveal a stoichiometry of ∼1 K per unit cell of MFI, limiting then the final K incorporation within siliceous MFI crystals at ∼0.7 wt %. Above this stoichiometry, K is not incorporated into the final solids unless significant amounts of Sn are simultaneously present, leading to the formation of tin-silicate precipitates. The optimized PtSn@K-MFI catalysts improve the catalytic performance of well-established references, as PtSn/SiO 2, for the propane dehydration (PDH) reaction. In particular, low Sn loadings (below 0.5 wt %) result in higher time-on-stream (TOS) deactivation catalytic profiles but excellent regenarability after consecutive PDH reaction, while higher Sn content (close to 1 wt %) minimizes TOS deactivation due to the maximization of Pt–Sn bonds but consecutive regenerations result in significant metal sintering. Increasing Sn contents within MFI crystallites facilitates Pt sintering and, thus, occurring catalyst deactivation upon regeneration cycles. As a result of complex interconnected nucleation/crystallization processes, fine-tuning rationalizations of one-pot synthesis approaches can substantially influence the final atomic and subnanometric metal interactions and, consequently, the catalytic and sintering-resistance properties when exposed to highly demanding industrial conditions.