Delignification of Eucalyptus globulus saplings in two organosolv systems (formic and acetic acid): Preliminary analysis of dissolved lignins

Organosolv delignification of 2–3 years old Eucalyptus globulus with formic or acetic acid produced bleachable grade pulps with kappa number values of 20–35. Pulp yields for the acetic acid treatment (45–55%) were higher than for formic acid (32–46%) although also they showed the greater kappa number.Delignification was modelized by means of the accomplishment of respective factorial designs of experiments. Data were successfully fitted by mathematical models for prediction of pulp yield and kappa numbers from the process variables.Recuperation of the dissolved lignin, by means of water precipitation, allowed the recovery of about a 20% of the initial raw material (about 80% of lignin).Chemical and spectroscopic analyses for the determination of the contents of main functional groups in lignin were made and C9 formulae calculated, as follows: C9H7.58O2.34(OCH3)0.80(COOH)0.18(OHAr)0.35(OHR)0.58 and C9H6.14O1.55(OCH3)1.09(COOH)0.18(OHAr)0.52(OHR)0.58 for the products obtained with formic acid and acetic acid, respectively.