Coprecipitation of Sn and Al Precursors to Create Additional Acid Sites of Pt/Sn-Al2O3 Catalysts for Propane Dehydrogenation

Alumina-supported PtSn catalysts have been industrialized as the major catalysts for propane dehydrogenation, where Sn serves as an essential promoter. Herein, we synthesized a variety of Sn-doped alumina supports by regulating the precipitation order of Sn and Al precursors as follows: Sn precursor precipitated before Al, coprecipitated with Al, precipitated immediately after Al, or precipitates after 2 h of Al. The effect of Sn promoter on the surface acidic properties of alumina and, ultimately, on propane dehydrogenation was further investigated. The Sn species introduced by coprecipitation in alumina created additional surface strong acid sites, attributed to more Sn⁴⁺ species on the surface, which are able to remain stable during the subsequent treatment. Consequently, the coprecipitated Sn species in the corresponding catalyst donate more electrons to Pt and reduce the metal particle size. As a result, the catalyst with Pt supported on the coprecipitated support (Sn+Al) exhibits superior initial propane conversion (43.2%) and stability (k_d = 0.035 h⁻¹). This study provides new insight into the interaction between the two key components, tin promoter and alumina support, of Pt/Sn-Al₂O₃ catalysts.