Development of meso-microstructure in MFI zeolites via nanocrystalline cellulose templating for conversion of lignocellulosic biomass to aromatic hydrocarbons

摘要

The microporous system in ZSM-5 zeolite is crucial in the upgrading of pyrolytic intermediates to gasoline-range aromatic compounds in catalytic pyrolysis of lignocellulosic biomass. However, some oxygenates derived from lignocellulosic biomass that are too large to enter the micropores cause serious coke formation and result in catalyst deactivation. Herein, the hierarchical ZSM-5 zeolite catalyst was prepared with hydrothermal recrystallization using nanocrystalline cellulose as a green template tosynthesize zeolite with meso-micro hierarchical structure. The effect of mesoporosity in the zeolite on product distributions and selectivity was investigated in correlation to the loading of biopolymer as a template in the modification treatment. Hydrothermal recrystallization of ZSM-5 with the presence of nanocrystalline cellulose increased the surface area (356.8 m2/g) and mesoporous pore volume (0.159 cm3/g) without disturbing the original microporous framework. Results of catalytic pyrolysis showed the secondary mesopores promoted the conversion of bulky oxygenated intermediates and mitigated the polymerization reaction in the microporous system of ZSM-5. Additionally, the hierarchical ZSM-5 modified with nanocrystalline cellulose achieved aromatic hydrocarbons (mono-rings and 2-rings) relative content at 60.44% enhanced from 15.12% in parent ZSM-5 at the same investigated condition.