In situ synthesis of Pt nanoparticles encapsulated in silicalite-1 zeolite via a steam-assisted dry-gel conversion method

In this work, Pt nanoparticles (NPs) were directly encapsulated into MFI-type zeolite (Pt@S-1) via a steam-assisted dry-gel conversion method. The synthesis process included the disaggregation of Pt immobilized SiO2–SH spheres and the in situ crystallization for the synthesis of Pt@S-1. The Pt NPs remained stable during the whole crystallization process and the average size of Pt NPs in the synthesized Pt@S-1 was from 1.54 to 2.34 nm. The highest encapsulation degree of Pt NPs was calculated as 93.8% and decreased slightly to 84.9% with the increase of Pt loading. Owing to the high encapsulation degree of Pt NPs in MFI crystals, the size of Pt NPs after calcination at 800 °C only grew up to 3.19 nm showing significantly high thermal stability. The uniform microporous pores of silicalite-1 zeolite as well as the small size and stable Pt NPs endow the Pt@S-1 catalyst with high activity and stability in the nitrobenzene hydrogenation reaction.