A series of Pt-Ir bimetallic catalyst and monometallic catalysts were prepared by impregnation method. The activity, selectivity and activity maintenance of the HY-Zeolite and $γ-Al_2O_3$ supported catalysts were determined under flow conditions at 1 atm for the conversion of n-hexane. Additional catalyst characterization was provided by hydrogen chemisorption.
Activity, selectivity and activity maintenance of the pt-Ir bimetallic catalyst was not affected by catalyst calcination temperature. Significant decrease in dispersion was observed for iridium monometallic catalysts, but small decrease in dispersion was observed for platinum and platinum-iridium bimetallic catalysts.
For Pt-Ir/$γ-Al_2O_3$, the highest activity and enhanced activity maintenance were observed at 500℃. Also, Pt-Ir/$γ-Al_2O_3$ gave higher selectivity for benzene and cracking reaction than Pt-Ir/HY-Zeolite, while, for Pt-Ir/HY-zeolite the highest activity and enhanced activity maintenance were observed at 350℃. Also, Pt-Ir/HY-zeolite gave higher selectivity for isormerization reaction, than Pt-Ir/$γ-Al_2O_3$.
Because the Pt-Ir bimetallic catalysts showed platinum like activity and selectivity, the 0.5 wt% Pt-0.5 wt% Ir bimetallic catalyst surface composition seems to platinum rich phase.
When iridium is present the catalysts are much more stable, and have much higher selectivity for cracking reaction.