Synthesis Of Hollow MFI Zeolite Supported Catalyst And Catalytic Performance Study For Hydrodeoxygenation Of Biomass

Developing green and sustainable aviation fuel has attracted significant attention due to the gradual depletion of fossil resources and stringent environmental regulation as well as the rapid development of aviation industry.Biomass is the only renewable organic carbon resource in nature,which endow it with unique advantages in producing a variety of value-added chemicals and liquid fuels.In this paper,lignin-derived oil and vegetable oil were used as feeds to synthesize cycloalkanes and paraffin components in aviation fuel,which provided theoretical guidance for one step conversion of biomass into high quality aviation fuel.Firstly,the hollow hierarchical S-1 zeolite was synthesized using the dissolution-recrystallization method,and the effect of dissolution-recrystallization time on the formation of hollow structure was studied.Compared with solid S-1 zeolite,the hollow S-1 zeolite had a larger mesoporous pore volume and an external specific surface area,and there were more non-equivalent Si(4 Si)groups,indicating that it contained more crystal defects.The center of the zeolite crystal preferentially dissolved,eventually forming the hollow structure.The hollow ZSM-5 zeolites with different silicon aluminum ratios were synthesized by introducing Al species during the dissolution-recrystallization process,and the Al species existed in the zeolite framework in the form of tetrahedral coordination.The introduction of Al species had no effect on the formation of hollow structure.Then,the hydrodeoxygenation of lignin-derived oil model compound guaiacol over different Pt catalysts were prepared by using hollow MFI zeolites as support were investigated.Experimental results indicated the hollow structure promoted the diffusion of reactants and intermediates,and accelerated the reaction rate.The metal sites were responsible for the hydrogenation of guaiacol aromatic rings while Pt-deposited acidic supports were indispensable to the deoxygenation of oxygenates.Moreover,the hollow Pt/h ZSM-5 catalyst achieved 100%cycloalkanes selectivity at the low temperature of220°C,the catalytic activity didn't change during the stability evaluation period of 10h,and the carbon deposition amount was only 5.0 wt%,showing excellent low temperature hydrodeoxygenation activity,catalytic stability and carbon deposition resistance.The acidity enhancement of the hollow ZSM-5 zeolites were beneficial to the isomerization-demethylation of cyclohexane to form cyclopentane,which had no effect on the hydrodeoxygenation product species.Finally,the Pt Ni@h S-1 catalyst with yolk-shell structure was synthesized using the ship-in-bottle strategy for hydrodeoxygenation of vegetable oil model compound methyl stearate to synthesize paraffin components in aviation fuel.Compared with Pt/S-1 catalyst,the introduction of additive Ni improved the hydrodeoxygenation activity and selective cracking ability of catalyst,therefore improved the selectivity of aviation fuel components.The yolk-shell structure increased the contact time of the reactants and intermediates with the metal and acid sites,thereby improved the selectivity of aviation fuel components with a selectivity up to 45%,and facilitated the deoxygenation path of DCO₂.The active metal loading position had little effect on the selectivity of deoxygenation pathway,and the increase in the number of acid sites of catalyst support was advantageous to DCO deoxygenation path.