Organosolv pulping — V: Formic acid delignification of Eucalyptus globulus and Eucalyptus grandis

Abstract

Organosolv pulping mediated by formic acid was evaluated. Wood of Eucalyptus globulus and Eucalyptus grandis was cooked with formic acid under different conditions of solvent ratio (formic acid: water), catalyst concentration, temperature and time of treatment. For E. globulus, the best results for sawdust samples were obtained at 90°C after 90 min of cooking, with a solvent ratio of 80:20 (vv⁻¹), a charge (wood:solvent ratio) of 1:30 and 0·44% (vv⁻¹) of catalyst. In the case of E. globulus chips, the concentration of catalyst used was 0·22%, the charge was 1:10, and soaking and preheating were used. For a sample of E. globulus soaked in water for 72 h, the pulp yield was 56%, Kappa number 22 and reject content 1·6% E. grandis wood needed more drastic conditions. Cooking of E. grandis chips with formic acid (99%) at 95°C, 0·22% catalyst, charge 1:10, resulted in a pulp yield of 43%. The Kappa number was 31, reject content 0·1% and the cellulose and Klason lignin contents were 88% and 8%, respectively.