Silicon: A Surface Dopant for Stable Alumina-Supported PtGa Propane Dehydrogenation Catalysts by Favoring Redox and Carbon Dynamics

The exploitation of shale gas has stimulated the use of on-purpose propane dehydrogenation (PDH) technologies. These technologies rely on continuous and rapid catalyst regeneration to maintain high propene production. For Pt-based catalysts, metal promotors and additives, such as Ga and Si, have been shown to enhance the catalyst productivity and stability. While most studies have focused on understanding the role of Ga as a promoter, the effect and role of Si on the catalytic properties are less explored and understood. Therefore, tailored monometallic Pt and bimetallic Pt–Ga catalysts supported on alumina or Si-doped alumina are prepared via surface organometallic chemistry and evaluated under PDH conditions. The Pt catalyst containing both Ga and Si displays the highest propene productivity (1970 mol_C3= mol_Pt^–1 h^–1 after 2 h) and the lowest deactivation constant (0.31 h^–1 after 2 h), pointing out the critical role of both Ga and Si. While scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray absorption spectroscopy show that the catalyst structures of the as-reduced Pt–Ga catalysts are similar, postmortem analyses reveal that Si-doping of the alumina-supported Pt–Ga PDH catalyst modifies redox and carbon dynamics. This modification maintains Pt-active sites by yielding interfaces between Pt and GaO_x domains along with a surface PtC structure that is correlated with increased structural dynamics and slower deactivation.