Highly Stable Nb₂O₅–Al₂O₃ Composites Supported Pt Catalysts for Hydrodeoxygenation of Diphenyl Ether

Various TiO₂, SiO₂, Al₂O₃, and Nb₂O₅–Al₂O₃ supported Pt catalysts have been prepared by urea precipitation method for catalytic hydrodeoxygenation (HDO) of diphenyl ether (DPE) as a 4-O-5 aryl-ether lignin model compound. The selectivity toward deoxygenated product cyclohexane increased obviously with Nb₂O₅·<i>n</i>H₂O decorated, owing to the significant promotion effect of NbO_<i>x</i> species and acid sites on C–O bond cleavage. At higher pressure (3.0 MPa H₂), DPE underwent a HYD route, while direct hydrogenolysis route occurred at low pressure (0.1 MPa H₂). In addition, the reaction rate constants and activation energies were obtained in the temperature range from 160 to 220 °C. Based on the Arrhenius law, the activation energy for the cleavage of the C–O bond in DPE was calculated to be 91.22 kJ/mol. It was noteworthy that the Pt/20Nb–Al₂O₃ showed higher stability than Pt/Al₂O₃ for hydrodeoxygenation of diphenyl ether, which can be attributed to its water-tolerant Lewis acid sites