Increasing the bio-aromatics yield in the biomass pyrolysis oils by the integration of torrefaction deoxygenation pretreatment and catalytic fast pyrolysis with a dual catalyst system

The integration of Torrefaction Deoxygenation Pretreatment (TDP) and Catalytic Fast Pyrolysis (CFP) with dual catalysts was employed to improve the yield of bio-aromatics (BTX) derived from Miscanthus. Results showed that the TDP could effectively remove the oxygen content up to 38.16% at 280 °C. This resulted in a remarkable reduction of undesired oxygenate compounds in the pyrolysis oil. With ZSM-5 catalyst, the dominant components in pyrolysis oil became aromatic hydrocarbons (up to 66.29%) instead of oxygenates. The selectivity of bio-BTX increased with the increase of torrefaction temperature up to 56.63%. For the pyrolysis process, the highest yield (37.54%) and selectivity (56.63%) of bio-BTX were obtained at 600 °C. Compared with ZSM-5, the addition of CaO and MoO3 promoted bio-BTX yield due to the enhanced deoxygenation and olefins aromatization. The integrated TDP and CFP with ZSM-5 and MoO3 significantly improved the selectivity of bio-BTX, reaching the highest selectivity of 70.69% and a yield of 51.07%. Combining these two processes can enhance bio-aromatics yields from biomass, thus considerably improving the quality and value of the liquid product.