Kinetics of Eucalyptus globulus Delignification in a Methanol−Water Medium

Abstract

The kinetics of Eucalyptus globulus delignification in methanol−water pulping has been studied. A total of 17 isothermal runs at a liquor-to-wood ratio of 50 L kg-1 were carried out to develop the kinetic model describing the system. In a first series of experiments, eight models were considered to 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 species: initial, bulk, and residual lignin, their content in wood being 10, 69, and 21%, respectively. Initial and residual delignification were considered 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 reproducing 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 industrial operating conditions.