Abstract
<jats:p>The increasing propylene demand-and-supply gap accelerates the development of on-purpose propane dehydrogenation (PDH) technologies. In industrial PDH processes, Pt-Sn based catalysts have had a major impact due to their specific catalytic performances, despite few shortcomings and need for further optimization. Thus, large research efforts have been centered on identifying the roles of the Sn-promoter, including the use of surface organometallic chemistry (SOMC). While so far, SOMC has been mostly used to identify the role of Pt-Sn alloying, the focus here is to explore the speciation of the surface and interfacial Sn sites across synthetic steps. A Pt-Sn catalyst supported on alumina is thus prepared via SOMC, and the detailed spectroscopic and microscopy characterization allows monitoring the evolution of Sn sites, evolving from SnIV sites after grafting to SnII sites, best described as SnII single atoms, upon thermal-treatment. Subsequent grafting of Pt and H2-treatment yield small and narrowly distributed Pt-Sn nanoparticles, which are active, selective and stable for PDH, while residual well-defined SnII sites remains. Notably, while SnII single atoms co-exist with PtSn alloy, this study pinpoints that these SnII single atoms dispersed on alumina display specific 119Sn NMR signatures, that is difficult to distinguish SnII from Sn0 sites solely based on their XAS signatures.</jats:p>