Hydrocarbon-Rich Bio-Oil Production from Catalytic Pyrolysis of Biomass over the Undervalued ZSM-11 Zeolites

Catalytic fast pyrolysis (CFP) is advantageous in converting biomass waste into biofuels, wherein the catalyst plays a critical role. Although the ZSM-5 zeolite has been screened as the most efficient catalyst for deoxidizing biomass, its sinusoidal 10-membered ring (MR) channels restrict the diffusion of biomass intermediates and always lead to catalyst deactivation. Inspired by "straightening the channel,"the ZSM-11 zeolite with a pore size similar to ZSM-5 but straight 10-MR channels was tested for biomass CFP. A series of nanosized ZSM-11 with silicon-to-aluminum ratios of 30, 40, 50, 100, 200, and ∞ were synthesized and characterized. In the CFP of maize straw, the moderately acidic ZSM-11(40) performed best in boosting hydrocarbon production and inhibiting coke formation. The deoxygenation capability of ZSM-11(40) was even higher than that of ZSM-5(40), as evidenced by the higher hydrocarbon selectivity and bio-oil yield. In addition, the straight 10-MR channels and nanorod morphology of ZSM-11(40) also suppressed the condensation of monoaromatics to polyaromatics in the CFP of various feedstocks (e.g., maize straw, lignin, and cellulose). Finally, the nano-ZSM-11(40) exhibited excellent reusability by maintaining its structural integrity and catalytic activity after three reuse cycles, which endowed it a promising but undervalued catalyst candidate for biomass CFP.