|Authors: (Changjun Liu and Yong Wang, The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, USA, and others)
Biomass is the only renewable source of carbon-based fuels and chemicals. Lignocellulosic biomass contains about 45 wt% cellulose, 30 wt% hemicellulose and about 25 wt% lignin. Converting lignocellulosic biomass into valuable chemicals and
liquid fuels has been extensively studied for the past decade due to the abundance of lignocellulosic biomass. Gasification, pyrolysis and hydrolysis are three major thermochemical routes to depolymerize lignocellulosic biomass. Unlike fossil carbon
resources, biomass contains a large amount of oxygen which leads to the low heating value and other unfavorable properties of the resultant liquid products. Thus deoxygenation is particularly important in the case of fuels. Hydrodeoxygenation (HDO) is the most promising and efficient route to fulfill this purpose. Recent progresses in biofuel and bio-oil upgrading by hydrotreatment are summarized into three main catalytic
routes with respect to their feedstock, namely, conventional hydrodeoxygenation of biooil, aqueous-phase hydrotreating of sugars, and hydrodeoxygenation of lignin-derived compounds.