On the behaviour
of lignin and hemicelluloses during the acetosolv processing of wood
J. C. Parajó, J. L. Alonso and D. Vázquez
Department of Chemical Engineering, University of Vigo
(Campus Orense ), Las Lagunas, 32004, Orense , Spain
Received 10 February 1993;
revised 6 April
1993.
Available online 24 June
2003.
Abstract
Eucalyptus globulus wood samples were submitted to fractionation
with 95% acetic-acid solutions catalysed by small quantities of HCl.
Experiments were performed at the normal boiling temperature using a
liquor/wood ratio equal to 10 g/g. The effects of treatment time (0–180 min)
and catalyst concentration (0-0·2%) on pulp yield, solid residue composition
and cooking liquor composition were determined. Pulp yields in the range
51·5–90·6% were obtained. Extensive delignification of wood was achieved under
a variety of operational conditions, leading to solid residues with less than
4% lignin. The lignin removal was modelled kinetically as the contribution of
two parallel, first-order reactions. Pulps containing over 90% polysaccharides
and glucan/polysaccharide ratios higher than 0·95 were obtained under selected
conditions. Pentoses and furfural were identified as hemicellulose hydrolysis
products. The kinetics of hemicellulose saccharification was modelled assuming
two sequential, first-order, irreversible reactions. The maximum pentose
recovery accounted for 37% of the potential amount. Under the conditions
leading to optimum pentose recoveries, good delignification was achieved.
Furfural concentrations up to 4·3 g/l were obtained under the severest experimental
conditions studied.
Author Keywords: Acetic acid pulping; organosolvent
delignification; acetosolv processing; hemicellulose hydrolysis
No comments:
Post a Comment