Due to the high acid, oxygen and water contents of fast pyrolysis oil, it requires the improvement of its fuel properties by further upgrading, such as catalytic hydrodeoxygenation (HDO). In this study, Nb₂O₅ was evaluated as a support of Pd-based catalysts for HDO of fast pyrolysis oil. A Pd/SiO₂ catalyst was used as a reference. Additionally, the impact of iron as a promoter in two different loadings was investigated. The activity of the synthesized catalysts was evaluated in terms of H₂ uptake and composition of the upgraded products (gas phase, upgraded oil and aqueous phase) through elemental analysis, Karl Fischer titration, GC-MS/FID and ¹H-NMR. In comparison to SiO₂, due to its acid sites, Nb₂O₅ enhanced the catalyst activity towards hydrogenolysis and hydrogenation, confirmed by the increased water formation during HDO and a higher content of hydrogen and aliphatic protons in the upgraded oil. Consequently, the upgraded oil with Nb₂O₅ had a lower average molecular weight and was therefore less viscous than the oil obtained with SiO₂. When applied as a promoter, Fe enhanced hydrogenation and hydrogenolysis, although it slightly decreased the acidity of the support, owing to its oxophilic nature, leading to the highest deoxygenation degree (42.5 wt.%) and the highest product HHV (28.2 MJ/kg).

The social, economic, and environmental impacts of climate change have been shown to affect poorer populations throughout the world disproportionally, and the COVID-19 pandemic of 2020–2021 has only exacerbated the use of less sustainable energy, fuel, and chemical sources. The period of economic and social recovery following the pandemic presents an unprecedented opportunity to invest in biorefineries based on the pyrolysis of agricultural residues. These produce a plethora of sustainable resources while also contributing to the economic valorization of first-sector local economies. However, biomass-derived pyrolysis liquid is highly oxygenated, which hinders its long-term stability and usability. Catalytic hydrogenation is a proposed upgrading method to reduce this hindrance, while recent studies on the use of nickel and niobium as low-cost catalysts, both abundant in Brazil, reinforce the potential synergy between different economic sectors within the country. This review gathers state-of-the-art applications of these technologies with the intent to guide the scientific community and lawmakers alike on yet another alternative for energy and commodities production within an environmentally sustainable paradigm.