The Role of Metal and Acid Sites in the Liquid-phase Hydrodeoxygenation of Lignin-derived Phenolic Dimers

Bio-oil obtained from the depolymerization of lignocellulosic biomass is a potential alternative source to replace fossil fuels. However, due to high oxygen content, the bio-oil must be upgraded. In this direction, the hydrodeoxygenation reaction (HDO) is widely applied. Considering the complex chemical composition of the bio-oil, a variety of model molecules have been used in the literature to study the mechanism of the HDO process. In this work, we discuss heterogeneous catalysts and reaction conditions (temperature, pressure, and solvent) generally used for the HDO of dimeric aryl ethers representative of the main ether linkages present in the lignin:& alpha;-O-4, & beta;-O-4, and 4-O-5. The present work aims to shed light on the role of metal and acid sites and understand the influence of the reaction conditions on the reaction pathways.