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·nH2O decorated, owing to the significant promotion effect of NbO x 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.