Lignin Behavior During the Autocatalyzed Methanol Pulping of Eucalyptus globulus Changes in Molecular Weight and Functionality

Summary The molecular weight distribution and functional group contents (phenolic and carbonyl) of lignin samples from the autocatalyzed pulping of Eucalyptus globulus wood were determined. A total of 17 pulping runs were carried out at different conditions according to a surface response design experimental matrix (central composite). The influence of pulping temperature (170–200°C), pulping time (40–120 min) and methanol concentration (30–70%, w/w) on the characteristics of the isolated lignins was studied. Empirical models were developed and used to predict the lignin properties as a function of the cooking conditions. Under high temperature, long cooking time and low alcohol concentration, a rise in functional groups content and a drop in molecular weight of lignin