Characterization and Catalytic Properties of Pt-Ir Small Bimetallic Cluster in NaY

The formation of small Pt-Ir bimetallic clusters (about 1 nm) by the reducton of Pt and Ir co-ion-exchanged NaY with H₂ at 300°C after calcined with oxygen at 300°C was evidenced by temperature programmed oxidation/reduction (TPO/R), ¹²⁹Xe NMR, hydrogen chemisorption and catalytic probe reaction. These small Pt-Ir bimetallic clusters inside the supercage were more stable than Ir monometallic cluster and remained inside the supercage after re-oxidation treatment below 400°C. Temperature programmed oxidation/reduction (TPO/R) results suggested that the interaction between Pt and Ir takes place in the calcination step prior to hydrogen reduction. The Pt-Ir/NaY bimetallic catalyst showed a higher activity and better activity maintenance than those of Pt/NaY catalyst in n-heptane reforming reaction.