Bifunctional and Bimetallic Pt–Ru/HZSM-5 Nanoparticles for the Mild Hydrodeoxygenation of Lignin-Derived 4-Propylphenol

The development of bifunctional and bimetallic catalysts is of crucial importance for the bio-oils upgrading applications. To improve the quality of bio-oils as fuels, hydrodeoxygenation (HDO) is one of the most promising reactions for the upgrading of lignin-derived bio-oils. However, this process has been typically operated under high H2 pressures (40–50 atm). Therefore, the development of catalysts for the HDO of lignin-derived compounds operated under mild conditions is still a great challenge. In this context, the mild HDO of 4-propylphenol as a model bio-oil compound operated at atmospheric pressure using hierarchical bimetallic Pt–Ru/HZSM-5, prepared by co-impregnation of metals on zeolite nanoparticles obtained by a one-pot hydrothermal synthesis with the aid of tetrabutylphosphonium hydroxide as a dual structure-directing agent, is reported. The combination of Pt and Ru together with hierarchical structures of zeolites eventually results in the unexpectedly excellent catalytic performance toward the alkylcycloalkane production. Not only the presence of hierarchical structure provides the beneficial effect for promoting the high dispersibility of bimetallic active sites, eventually leading to a significant decrease in the nanometallic particle size (20.0 ± 8.0 to 2.7 ± 0.6 nm over conventional zeolite and hierarchical one, respectively), but also the synergistic effect of bimetallic Pt and Ru active sites can greatly enhance a very high yield of propylcyclohexane (100%). The synergistic bifunctional and bimetallic catalytic platform illustrates scientific opportunities toward bio-oil upgrading applications.