Hydrodeoxygenation of a bio-oil model compound derived from woody biomass using spray-pyrolysis-derived spherical γ-Al2O3-SiO2 catalysts

In this study, spherical γ-Al2O3-SiO2 catalysts with various Al/Si ratios were prepared by combining the sol-gel and spray pyrolysis (SP) methods. The effectiveness of the product catalysts was then tested via the hydrodeoxygenation (HDO) of guaiacol, a model compound of bio-oil obtained from the pyrolysis of lignocellulosic biomass. Our results showed that the γ-Al2O3-SiO2 catalyst with a 50:50 Al/Si ratio after calcination at 450 °C exhibited the highest guaiacol conversion (81.79%) at a reaction temperature of 300 °C, atmospheric pressure, and a weight hourly space velocity (WHSV) of 6.5 h−1. During guaiacol HDO, the carbon–oxygen cleavage and methyl group transfer reactions occurred on the γ-Al2O3-SiO2 catalyst, which converted the guaiacol into the respective deoxygenated products, including 2,6-xylenol, 2,3,5,6-tetramethyl phenol, pentamethyl benzene, and hexamethyl benzene. The reaction pathways for the conversion of guaiacol HDO were also proposed in this study.