Hydrodeoxygenation Performance of Lignin-Derived Phenolics to Cycloalkanes: Insights into the Crystal Structures of the Nb₂O₅ Support

Abstract

Hydrodeoxygenation (HDO) of lignin-derived phenolics is promising to produce high-value-added chemicals and liquid fuels. As a strong oxophilic support, Nb 2 O 5 maintains high catalytic activity for the deoxygenation of oxygen-rich reactants, while few studies have clarified the influence of crystal structures on reactivity. In this study, the Nb 2 O 5 supports with three crystal structures (pseudohexagonal-TT, orthorhombic-T, and monoclinic-H) were successfully prepared and used for the HDO of lignin-derived phenolics after loading bimetal Ni and Co. The structural properties and acidity of the supports and catalysts gradually deteriorated with the increase in calcination temperatures. The oxygen vacancy content and the interaction strength between supports and active metals followed the rule of Nb 2 O 5 -TT > Nb 2 O 5 -T > Nb 2 O 5 -H. In addition, oxygen vacancy content also had a volcanic relationship with the catalyst reduction times. Then, the catalytic activity of the catalysts was studied in the HDO reaction of guaiacol. The 10Ni−10Co/Nb 2 O 5 -TT (450 °C) catalyst exhibited the best catalytic performance with a complete conversion of reactant and a high cycloalkane selectivity of 98.6% under optimal conditions (250 °C, 3 MPa H 2 , and 3 h). More importantly, recycle tests indicated that it also had excellent stability. Moreover, other typical lignin-derived monomers and dimers were selected to test the reactant adaptability of the catalyst, and the selectivities of cycloalkanes also verged on the theoretical value. Therefore, the bifunctional catalyst composed of oxophilic Nb 2 O 5 -TT (450 °C) support and high-efficiency active metals possessed strong competitiveness in the HDO of lignin-derived phenolics.

Effect of Support on Steam Reforming of Ethanol for H₂ Production with Copper-Based Catalysts

“…Alumina is a widely used as a support in heterogeneous catalysis [33][34][35][36][37] due to its large surface area, good stability, and wide commercial availability [38]. Nb2O5 is also a notable material in the field of catalysis, known for its non-toxic nature, suitable acid properties [39,40], excellent chemical stability, high thermodynamic stability, low cost, and high commercial availability [41,42]. The combination of Nb2O5 with alumina is favorable because, being an n-type semiconductor, Nb2O5 can interact with copper in catalytic active reaction sites [43,44].…”