Ethane and propane dehydrogenation over PtIr/Mg(Al)O

• Preparation of supported Pt–Ir catalysts with characterization to confirm composition and alloy formation.
• Pt–Ir, and Pt–Sn catalysts both show superior performance over un-promoted Pt for the use of ethane dehydrogenation.
• DFT calculations over tetrahedral clusters of Pt4, Pt3Ir, and Pt3Sn elucidate experimental trend in activity.

Increased demand for light alkenes has motivated research on the catalytic dehydrogenation of the light alkanes and on understanding the role of catalyst composition on the activity, selectivity, and stability of Pt-based catalysts used for this purpose. The present study examines the structure and performance of Pt–Ir catalysts for ethane and propane dehydrogenation, and compares them with the performance of Pt and Pt–Sn catalysts. Nanoparticles of Pt, PtSn, and PtIr were prepared in a colloidal suspension and then dispersed onto calcined hydrotalcite (Mg(Al)O). After characterization to confirm formation of a bimetallic alloy, it was observed that at high conversions, Pt3Ir/Mg(Al)O exhibited lower initial activity than Pt3Sn/Mg(Al)O but greater stability to coke deposition. Intrinsic rate measurements at low feed residence time revealed the following trend in activity: Pt3Sn > Pt3Ir > Pt. DFT calculations carried out on tetrahedral clusters (Pt4, Pt3Ir, Pt3Sn) reveals that this trend in activity can be replicated and Ir is capable of alkane activation, a trait unique to this bimetallic system.

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