Pyrolysis of Woody Biomass Loaded with Phytic Acid in a Fluidized-Bed Reactor for Producing Levoglucosenone

Efficient conversion of lignocellulosic biomass into high-value chemicals remains challenging due to its complex structure. The selective production of levoglucosenone (LGO), a valuable bio-based building block derived from cellulose, has attracted increasing attention as part of efforts to establish sustainable chemical feedstocks. In this study, the continuous pyrolysis of woody biomass for LGO production was conducted using a fluidized-bed pyrolyzer, which is generally employed for bio-oil production but has not yet been tested for this reaction. Phytic acid (PA), a naturally occurring organic phosphorus compound abundant in agricultural residues, was employed as a biogenic catalyst and loaded over biomass. The pyrolysis characteristics were investigated in terms of LGO yield under various operating conditions of the fluidized-bed. Prior to PA loading, the removal of alkali and alkaline earth metals from feedstock biomass via oxalic acid-washing was examined to improve anhydrosugars yields. Thermogravimetric analysis (TGA) revealed that PA loading lowered the temperature of biomass pyrolysis and increased char yield, confirming its catalysis toward dehydration. TGA of model compounds of biomass components indicated PA catalyzed only cellulose pyrolysis, while it did not affect that of hemicellulose and lignin. In the continuous pyrolysis experiments, the best conditions achieved an LGO yield of 6.3 wt% (17.1 wt% on a cellulose basis) at an average bed temperature of 300 °C. The results demonstrate, for the first time, that a biogenic phosphorus catalyst such as PA can effectively promote LGO formation under continuous fluidized-bed operation. The study also provides fundamental insights for key factors affecting the LGO yield during steady-state operation of the fluidized-bed, such as the thermal stability of LGO and its interaction with char.