Kinetics of ASAM and Kraft Pulping of Eucalypt Wood (Eucalyptus globulus)

Summary The kinetics of ASAM and kraft pulping of eucalypt wood (Eucalyptus globulus) were studied in relation to delignification and polysaccharide removal. In comparison to kraft, ASAM pulping had lower mass losses and delignification for the same temperature and reaction times (59.2% at Kappa 25 vs 50.0% at Kappa 17, at 180°C). The ASAM pulps have a higher brightness. ASAM pulping had a short initial period with no mass loss and lignin removal, followed by two reaction phases: a main phase where 61% of lignin was removed (at 180°C) and a subsequent final phase. In comparison to kraft, the main delignification rates of ASAM pulping were approximately 2.5 slower (at 180°C, −1.8 × 10−2 min−1 for ASAM and −4.2 × 10−2 for kraft pulping), and the calculated Arrhenius activation energies were higher (132.4 kJ mol−1 and 83.5 kJ mol−1, respectively). The loss of cellulose was relatively small (12.5 %) and lower than in kraft pulps.