Hydrodeoxygenation of phenolic model compounds and catalytic upgrading of biomass pyrolysis vapors over Ni-promoted Nb2O5 catalysts

The hydrodeoxygenation (HDO) performance of Ni/Nb 2 O 5 catalysts promoted with Mo, Re, and V was evaluated using phenol and guaiacol as model compounds, followed by catalytic upgrading of pyrolysis vapors derived from kraft lignin, microalgae, and malt residues. Among the materials investigated, the Re-promoted catalyst (NiReNb) exhibited the highest intrinsic activity and selectivity, achieving complete deoxygenation of phenol to benzene and producing partially deoxygenated hydrocarbon intermediates from guaiacol. The superior performance of NiReNb correlates with smaller Ni crystallites, strengthened metal–support interactions, and the presence of additional Re-derived oxophilic sites, which collectively suppress undesired hydrogenolysis pathways and enhance selective C–O bond cleavage. When applied to real biomass-derived pyrolysis vapors, NiReNb substantially decreased the relative area percentage of oxygenated species, particularly oxygenated intermediates with multiple functional groups, while increasing the relative proportion of hydrocarbons and improving overall bio-oil quality. These results highlight the critical role of promoter-induced electronic and structural effects in governing HDO activity and product distribution, positioning NiReNb as a highly effective catalyst for the selective deoxygenation of both model compounds and complex biomass vapor streams.