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

Abstract

The positive role of pentacoordinated AlV 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 °C and 30 bar H2, 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 AlV 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.

Ni-Based Nanoparticles Catalyzed Hydrodeoxygenation of Ketones, Ethers, and Phenols to (Cyclo) Aliphatic Compounds

“…Consequently, considerable efforts have been devoted to the development of catalysts for selective HDO of oxygen-containing lignin model compounds (Scheme ), with heterogeneous catalysts based on Ru, − Rh, ,, Pt and Ir, , Pd. , In addition, non-noble mono- and bimetallic catalysts based on Ni, − Co, Ni–Ga, , Cu–Co–Ce, Ni–Mo–S, and Co–Mo–S have been reported. However, majority of these non-noble metal-based materials require high reaction temperatures and/or pressures − ,,,, and were mostly applied to a few substrates. − Consequently, there is a clear need for more efficient and selective heterogeneous HDO catalysts, particularly based on earth abundant metals due to their advantages with respect to availability, price, and toxicity.…”

“…15 Complete HDO involving both steps are challenging, and hence the majority of catalysts require harsh conditions and are mainly based on precious metals. 16−28 Consequently, considerable efforts have been devoted to the development of catalysts for selective HDO of oxygencontaining lignin model compounds (Scheme 2), with heterogeneous catalysts based on Ru, 16−19 Rh, 20,21,23 Pt 24 and Ir, 25,26 Pd. 27,28 In addition, non-noble mono-and bimetallic catalysts based on Ni, 29−47 Co, 48 Ni−Ga, 49,50 Cu−Co−Ce, 51 Ni−Mo−S, 52 and Co−Mo−S 53 have been reported.…”

“…Catalytic hydrodeoxygenation of aromatic oxygen-containing compounds requires the removal of oxygen and the reduction of the aromatic rings . Complete HDO involving both steps are challenging, and hence the majority of catalysts require harsh conditions and are mainly based on precious metals. − …”