Ni–NbOx Bifunctional catalysts for selective hydrodeoxygenation of m-cresol to toluene

• Ni-NbO x interfaces dispersed on silica greatly promote direct deoxygenation pathway of m-cresol. • Synergistic interplay between Ni (hydrogenation) and NbO x (oxophilicity) boosts deoxygenation activity. • Tuning the Ni/Nb ratio enhances toluene formation by up to 18-fold vs. Ni/Nb₂O₅. • Dispersing Ni and NbO x species on mesoporous silica (SBA-15) offers a strategy to prevent metal surface coverage caused by NbO x reduction, thereby increasing the number of exposed active sites The catalytic performances of a series of Ni supported on mesoporous silica (SBA-15) and niobia, as well as Ni-NbO x dispersed on SBA-15 were evaluated for the hydrodeoxygenation (HDO) of m-cresol at 300°C under atmospheric pressure. Under the reaction conditions, hydrogenation and C-C hydrogenolysis pathways yielding only oxygenated products dominated over the monometallic Ni catalyst. In contrast, the Direct DeOxygenation pathway (DDO) leading to toluene was significantly promoted when Ni was in contact with oxophilic NbO x surface. Tuning the Ni-Nb ratio on silica revealed a remarkable enhancement of the DDO rate constant. Indeed, the kinetic rate constant determined over 5Ni5Nb/SBA was about 11 times higher than that measured on the catalyst containing only the Ni phase. This enhanced performance can be attributed to the formation of well-dispersed Ni–NbO x interfacial sites, where the hydrogenation capability of Ni associate with the oxophilic character of Nb⁵⁺/Nb⁴⁺ species allowing to a more efficient activation of the C-O bonding and promoting the DDO reaction pathway. These results offer valuable insights for the rational design of selective catalysts for the transformation of lignin-derived bio-oils into aromatic hydrocarbons.