The role of beta-O-4 cleavage in acidic organosolv pulping of softwoods

Fibres and fibre bundles of Norway spruce (Picea abies) thermomechanical pu lp (TMP) were used as starting material for organosolv pulping. The solvent s investigated were methanol, ethanol, propanol, acetone, dioxane and dimet hyl sulphoxide at two or more volume fractions with water. An acid catalyst was required for significant delignification of the softwood and 0.005 mol /L H2SO4 was close to optimum at 175 degrees C. Delignification was signifi cant for solvent mixtures having Hildebrand solubility parameters in the ra nge of 11-15 (cal/cm(3))(1/2). The concentrations of beta-O-4 linkages in t he woodmeal and pulp lignins were estimated by dioxane/HCl (0.2 mol/L) acid olysis. An excellent correlation between the yield of acidolysis products ( mmol/g lignin) and lignin content after pulping was obtained for pulps cook ed in 15 different solvent/water mixtures, with each formulation having its unique solubility parameter and acidity function.