The catalytic wet air oxidation (CWAO) of lignin, obtained from sugar-cane bagasse, was evaluated through
kinetic studies of the process of aromatic aldehyde production. The operations were carried out in a high
pressure mechanically stirred slurry reactor, in a semibatch way, and in the presence of a palladium catalyst
supported on γ-alumina in a temperature range of 373−413 K, at a total pressure of 20 bar, where the partial
pressure of oxygen varied in a range of 2−10 bar. The lignin concentration was 60.00 kg/m3 in an alkaline
medium of 2 mol/L of NaOH. The lignin degradation reaction and the aromatic aldehyde buildup were described
by a kinetic model quantified by a complex series/parallel reaction network.
-In the present work a process of catalytic wet air oxidation of lignin obtained from sugar-cane bagasse is developed with the objective of producing vanillin, syringaldehyde and p-hydroxybenzaldehyde in a continuous regime. Palladium supported on -alumina was used as the catalyst. The reactions in the lignin degradation and aldehyde production were described by a kinetic model as a system of complex parallel and series reactions, in which pseudo-first-order steps are found. For the purpose of producing aromatic aldehydes in continuous regime, a three-phase fluidized reactor was built, and it was operated using atmospheric air as the oxidizer. The best yield in aromatic aldehydes was of 12%. The experimental results were compatible with those values obtained by the pseudo-heterogeneous axial dispersion model (PHADM) applied to the liquid phase.
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