Kinetics of Eucalyptus globulus delignification in a methanol-water medium

The kinetics of Eucalyptus globulus delignification in methanol-water pulpi ng has been studied. A total of 17 isothermal runs at a liquor-to-wood rati o of 50 L kg(-1) were carried out to develop the kinetic model describing t he system. In a first series of experiments, eight models were considered t o study the influence of temperature on the delignification rate. The most suitable model, which was discriminated according to statistical criteria, describes delignification as the consecutive dissolution of three lignin sp ecies: initial, bulk, and residual lignin, their content; in wood being 10, 69, and 21%, respectively. Initial and residual delignification were consi dered as irreversible reactions and bulk delignification as reversible. The influence of hydrogen ion concentration was taken into account by means of a general power-law expression. The model proposed was validated by reprod ucing the experimental data from four runs carried out under nonisothermal conditions and a liquor-to-wood ratio-of 7 L kg(-1), which are closer to in dustrial operating conditions.