Catalytic Valorization of Lignin Using Niobium Oxide

Abstract

There is a significant interest in valorization of lignin into chemicals. In this research, niobium oxide was tested as a catalyst for partial oxidation of lignin. Research objectives were to: (1) study the effect of temperature and catalyst loading on synthesis of aromatics from lignin, (2) study the effect of oxidants and rate of mixing on lignin oxidation, and (3) determine the reaction kinetics. Batch experiments were performed via a factorial design with catalyst loading (0.1–0.3 g) and temperature (70–90 °C) as factors. Results indicated that under optimal conditions of temperature of 90 °C, and catalyst loading of 0.5 g, 137.194 mg L−1 of vanillin and 30.290 mg L−1 of acetovanillone were produced. Oxidant type was found have a significant effect for vanillin production but not for acetovanillone. In addition, production of both vanillin and acetovanillone were independent of mixing. It is theorized that formation of aceto derivatives and vanillin under alkaline conditions were due to retroaldol cleavage of the α-hydroxy-γ-carbonyl structure of the lignin.