Pyrolysis and catalytic upgrading of pine wood sawdust over modified biochar catalyst in a tandem microreactor

A series of novel catalysts were prepared by modifying biochar (BC) with different metal loading (Fe, Zn) and thermal activation in different atmospheres (CO2, H2O). The catalysts were further used to upgrade the pyrolysis vapor from pine wood sawdust, aiming to produce high-quality bio-oil. The modified biochar catalyst exhibited strong deoxygenation ability to acids and ketones in bio-oil and effectively converted lignin-derived compounds into aromatic hydrocarbons and phenols. Subsequently, the catalyst (BC-Fe-CO2) demonstrating the highest yields of phenols and aromatics was selected for condition optimization. Different catalytic temperatures and biomass-to-catalyst ratios were compared to determine the optimal conditions for producing high-quality bio-oil. Phenolics and aromatic hydrocarbons content in the bio-oil reached 70 % at the optimal condition and the selectivity of monocyclic aromatic hydrocarbons in aromatic hydrocarbons reached 77 %. The properties of the biochar catalysts were characterized using BET, SEM, XRD, and XPS. The superior performance of the modified BC catalysts not only relied on its enhanced surface area and porous structure but also due to active Fe sites. The detail reaction pathways of the bio-oil catalytic upgrading were also proposed. These findings underscore the potential of modified biochar in pyrolysis and catalytic upgrading for bio-oil with improved quality. [Display omitted] •Novel modified biochar was prepared with Fe/Zn loading and CO2/H2O activation.•Fe-modified biochar, activated in CO2, best improves oil to aromatic compounds.•The selectivity of monocyclic aromatic hydrocarbons reached 77 % at 923 K.•The reduced Fe3+ and porous structure in the biochar mainly drive the reactions.