Recovery of vanillin from Kraft lignin oxidation by ion-exchange with neutralization

This paper deals with the recovery of vanillin from Kraft lignin oxidation using an ion-exchange process with neutralization. In order to produce vanillin, oxidation of lignin takes place in the presence of alkaline medium (pH 12-13); under such condition almost all vanillin is present as vanillate. The goal of this work is the vanillin recovery that is achieved by passing the vanillate solution through a column packed with ion-exchange resin in H+ form (Amberlite IR120H) and the vanillate species is converted to vanillin form. This ion-exchange process is coupled with neutralization reaction in presence of a buffer solution (vanillate/vanillin). A set of batch equilibrium experiments (uptake curves) has been evaluated in order to obtain the concentration evolution of the vanillin, vanillate species and pH with time until equilibrium between the liquid and resin phases is established. The fixed-bed ion-exchange Na+/H+ has been analyzed at laboratory scale, and the evolution of vanillin, vanillate and pH was studied. A mathematical model for both batch and fixed-bed systems is presented that considers intraparticle diffusion controlled neutralization of the cationic resin by the system vanillin/NaOH. The developed modelling predicts uptake curves evaluated by batch experiments and breakthrough and elution curves evaluated by fixed-bed experiments. It has been verified that the ion-exchange processed through the column filled with ion-exchanger in H+ form can be useful for recovery vanillin from the alkaline solution provided from the process of Kraft lignin oxidation. (c) 2006 Elsevier B.V. All rights reserved.