Catalytic Oxidation of Kraft Lignin in a Trickle-bed Continuous Reactor.

For the first time, the catalytic oxidation of Kraft lignin over a solid heterogeneous catalyst was studied in a continuous lab-scale trickle-bed reactor. This catalytic process is able to depolymerize Kraft lignin and produce phenolic compounds of interest such as vanillin. The impact of operating conditions such as temperature, residence time, contact time, catalyst loading and lignin concentration was evaluated. The formation of vanillin, the main phenolic compound detected in reaction products, was favored at medium temperature (200°C), short contact time (< 1 gcat.min.gfeed-1), high catalyst loading (32 g) and low lignin concentration (5 g.L-1). The vanillin productivity is 30 times higher in a continuous fixed bed reactor than in a batch reactor.