Recent advances in thermochemical conversion of biomass into drop-in fuel:a review

Abstract

The global evolutional changes towards the use of renewable energy sources for trans- portation purposes are on the increase in an attempt to mitigate the environmental haz- ard and the proposed depletion associated with fossil fuel resources. Pyrolysis and hy- drothermal processes of biomass conversion into renewable biofuels are resulted into the production of biocrude with high oxygen content due to the presence of large amount of oxygenates in biomass feedstocks. The presence of oxygen content in bio-oil causes cor- rosion, low heating value, instability and high viscosity in bio-oil. These challenges have necessitated the application of upgrading techniques such as catalytic hydrodeoxygenation process among others. The presence of several oxygenated compounds made the mech- anisms of bio-oil synthesis difficult and model bio-oil were reviewed to understand the effects of process parameters and catalysts on aromatic selectivity and conversion. The se- lectivity of aromatic hydrocarbons was affected by deactivation of catalysts’ active sites. Coke formation has been identified as one of the common and notorious causes of cata- lysts’ deactivation which is dependent on the nature of feedstock, conditions of operation and the nature of catalyst. Therefore, the need to develop, evaluate a structurally and ther- mally stable catalyst with high catalyst recovery and reusability are of importance in the quest to depict hydrodeoxygenation process as an excellent technique for bio-oil upgrad- ing.