Highly dispersed platinum clusters anchored on hollow ZSM-5 zeolite for deep hydrogenation of polycyclic aromatic hydrocarbons

Abstract

Deep hydrogenation of polycyclic aromatic hydrocarbons is a feasible strategy to acquire high-performance aviation fuels, in which the key is to design highly active hydrogenation catalysts. Herein, hollow ZSM-5 (HZ) and silicalite-1 (HS) zeolites with hierarchical porous architectures were manufactured through a post-alkali treatment strategy, and further supported Pt to fabricate Pt/HZ-WI, Pt/HZ-SEA and Pt/HS-SEA catalysts employing wet impregnation (WI) and strong electrostatic adsorption (SEA) methods. The SEA catalysts presented higher metal dispersion, more election-deficient Ptδ+ species and stronger spillover hydrogen ability, thus resulting in better intrinsic hydrogenation properties in the deep hydrogenation reaction of phenanthrene than the WI ones. Moreover, Pt/HZ-SEA catalyst showed the supreme catalytic activity and the lowest activation energy of 52.11 kJ·mol−1 due to more hydrogenation active sites generated by the highly dispersed Pt clusters and the accelerated diffusion of reactants via the hierarchical porous architectures. Almost 100% selectivity to the deep hydrogenation products was achieved at rather low temperature of 220 °C. The Pt/HZ-SEA also displayed outstanding activity for hydrogenation of naphthalene, acenaphthylene and fluorene and excellent sulfur resistance. Furthermore, the acidic sites in HZ zeolite were favorable to boost the formation of electron-deficient Ptδ+ species having stronger deep hydrogenation ability and intensify the additional hydrogenation route through the spillover hydrogen. Finally, the DFT calculation results further verified that the Ptδ+ substances could heighten the adsorption of polyaromatics, thereby improving the deep hydrogenation activity.