Structural dynamics of PtSn/SiO2 for propane dehydrogenation

Abstract

PtSn bimetallic catalysts are among the best-performing propane dehydrogenation (PDH) catalysts. However, understanding these catalysts remains limited due to the intricate nature of bimetallic systems and their dynamic structural evolution under reaction conditions. To address this challenge, we employ various in situ/operando techniques, including UV-vis, CO diffuse reflective infrared Fourier transform spectroscopy (CO-DRIFTS), near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), and operando X-ray absorption spectroscopy (XAS), to elucidate the structural dynamics of PtSn/SiO₂ catalysts under reduction and working conditions. Our investigation reveals that the interactions between Pt, Sn, and SiO₂ support are strongly influenced by the synthesis procedures and the initial catalyst structure. Exposure to H₂ causes a reversible Sn–OH formation observed by modulation excitation spectroscopy (MES). A sequentially impregnated catalyst with a nominal Pt : Sn ratio of 1 : 3 and a co-impregnated catalyst with a ratio of 1 : 2 exhibit optimal performance for PDH. Despite distinct synthesis procedures and bulk structures, these two catalysts exhibit comparable surface properties and PDH performance, attributed to the dynamic migration of Sn species and formation of a Pt-rich metal surface under reductive atmospheres.