Recent advances in heterogeneous catalysts for biocrude hydrodeoxygenation

Abstract

Hydrodeoxygenation (HDO) of biocrude into chemicals and transportation fuels represents a promising avenue for the sustainable utilization of biomass-derived biocrude oil, obtained through pyrolysis or liquefaction. Catalysts play a pivotal role in this process, providing active metal sites for hydrogenation and hydrogenolysis, alongside acid sites for ring-opening, cracking, and C–O bond cleavage. Despite its potential, previous studies have often reported low HDO rates, leading to rapid catalyst deactivation and the formation of undesirable byproducts. Thus, the careful selection of catalysts that achieve an optimal balance between metal and acid functionality is critical. This review systematically examines the properties of biocrude produced by various techniques and the catalysts used in HDO of biocrude and its model compounds. Particular attention is given to the roles of sulfided metals, noble metals, non-noble metals as catalysts as well as various supports in HDO reactions. The influence of catalyst characteristics, including metal particle size, acid type and strength, and support structure, on HDO activity and product distribution is thoroughly analyzed. Additionally, factors contributing to catalyst deactivation are discussed. Finally, the review addresses current technical challenges and offers future perspectives on the development of catalysts with improved HDO activity and stability.