<i>n</i>-Butane Isomerization over Platinum-Loaded Crystalline Zr₃SO₉ in the Presence of Hydrogen

The platinum (Pt)-loaded crystalline Zr3SO9 catalyst (Pt/Zr3SO9) was used for the isomerization of n-butane under a hydrogen stream. Pt/Zr3SO9 exhibited substantially higher catalytic activity for this reaction, showing a weight-based activity approximately four times greater than that of the conventional Pt-loaded sulfated zirconia (ZrS) catalyst (Pt/ZrS), which has been widely used as an industrial catalyst for this reaction. In Pt/Zr3SO9, Pt particles formed a core–shell like structure consisting of Pt sulfide covered with metallic Pt (PtS@Pt), which were preferentially deposited on the lateral surfaces of the hexagonal sheet crystals of Zr3SO9 after heat treatment under flowing hydrogen. During heat treatment under a hydrogen stream, hydrogen molecules were dissociated on the PtS@Pt particles, and the resulting hydrogen atoms spilled over onto the Zr3SO9 crystal. These hydrogen species migrated through the Zr3SO9 structure, hydrogenating μ3-oxygen in the crystal structure to form H2O bound to the Zr sites, accompanied by the generation of oxygen defects. We proposed that these oxygen defects activate the hydrogen species to form hydrides, which play a crucial role in catalysis.