Synergistic Effect in Vapor Phase Hydrodeoxygenation on USY Zeolite Supported Ir-Pt Catalyst: Role of Pentacoordinated Al3+ Ions

The positive role of pentacoordinated Al-V sites on the catalyst behavior was evidenced in the vapor phase hydrodeoxygenation (HDO) of phenol over Ir-, Pt-, and Pt-Ir catalysts supported on USY and ZSM-5. All catalysts showed bifunctionality in the HDO reaction at 310 degrees C and 30 bar H-2, the more acidic USY zeolite being more efficient as a support than ZSM-5, and the metal function decreasing in the order Ir-Pt > Pt >> Ir. The superior activity of Ir-Pt/USY was attributed to the cumulative effects of the support acidity, the smaller zeolite crystal size, the higher amount of unsaturated Al-V sites, and the synergy between acid and metal sites. The promotion of Pt with Ir improved the reducibility of platinum, the catalyst's overall oxophilicity, and its active phase dispersion.