Enhanced production of hydrocarbons from the catalytic pyrolysis of maize straw over hierarchical ZSM-11 zeolites

Abstract

The ZSM-11 zeolite has been revealed as an undervalued catalyst for the catalytic fast pyrolysis (CFP) of biomass to produce hydrocarbon-rich bio-oil. However, the importance of hierarchical ZSM-11 in bio-oil production is still unknown. Herein, a series of ZSM-11 with varied morphologies, acidities, and secondary mesopores were synthesized and tested as catalysts in the CFP of maize straw. For the morphology series, ZSM-11 with separate nanorods (Nano-ZSM-11) or aggregated nanosized single-crystal (NS-ZSM-11) performed better in bio-oil production than microsized Micro-ZSM-11. Regarding the NS-ZSM-11 series, optimal acidity facilitated the deoxygenation of biomass vapor, while introduced intracrystal mesopores tended to improve bio-oil yield. NS-ZSM-11(20)-0.3 possessing both adequate acidity and coupling inter/intracrystal mesopores led to a satisfactory bio-oil yield (23.6 wt%) and hydrocarbon selectivity (63.6 area%), which were 1.1 and 1.3 times those for Nano-ZSM-11 (bio-oil yield: 22.0 wt%; hydrocarbon selectivity: 47.8 area%), respectively. NS-ZSM-11(20)-0.3 also showed excellent reusability in regeneration-pyrolysis cycles.