Highly Dispersed Rh/NbO<sub><i>x</i></sub> Invoking High Catalytic Performances for the Valorization of Lignin Monophenols and Lignin Oil into Aromatics
Weixiang Guan, Xiao Chen, Chi Wing Tsang, Haoquan Hu, Changhai Liang
Abstract
As fossil fuels are constantly depleted, valorization of lignocellulosic biomass into valuable aromatic compounds is of great significance but exceedingly challenging. In this work, the structure and catalytic performance of various Rh/Nb2O5 catalysts were studied in detail via the catalytic hydrodeoxygenation of a representative lignin monophenol compound 2-methoxy-4-propylphenol. The best catalytic performance was obtained over Rh/Nb2O5-400 (Nb2O5 calcined at 400 °C) with an exceptional 98% yield of propylbenzene under 0.5 MPa H2, which was mainly due to the cooperation between highly dispersed Rh metals and NbOx species, in which Rh was responsible for dissociation of H2 and NbOx for breaking of C–O bonds at the metal–support interface. Besides, the lignin oil obtained in depolymerization of raw pine wood was directly used as the substrate in the catalytic hydrodeoxygenation reaction over the Rh/Nb2O5-400 catalyst under 0.5 MPa H2. Encouragingly, the liquid products were identified and found that lignin oil was completely converted into C6–C10 hydrocarbons (>99% selectivity) with an 80.1 mol % yield of aromatics. The results achieved in this work highlighted that high-value utilization of lignocellulosic biomass feedstocks to produce aromatic chemicals and liquid fuels could be achieved over Rh/Nb2O5 under a low hydrogen pressure.