KINETICS OF ACID-CATALYZED DELIGNIFICATION OF EUCALYPTUS-GLOBULUS WOOD BY ACETIC-ACID

The kinetics of HCl-catalysed delignification of Eucalyptus globulus w ood by 70% (w/w) acetic acid solution were satisfactorily explained by a model in which 5% of the lignin fraction could not be eliminated an d the remaining 95% was eliminated by a single process which, in view of the activation energy calculated from the data was attributed to th e hydrolysis of a-aryl ether bonds. The selectivity of the process was effectively independent of HCl concentration and operating temperatur e for pulp yields > 50%. At high temperature (160 degrees C) and catal yst concentration (0.027 M HCl), lignin condensation and precipitation became significant and the data were better fitted by a model compris ing two consecutive processes: lignin solubilization followed by ligni n condensation.