ACETOSOLV PULPING OF PINE WOOD - KINETIC MODELING OF LIGNIN SOLUBILIZATION AND CONDENSATION

Experiments of delignification of Pinus pinaster wood by acetic acid a t atmospheric pressure showed that acetic acid concentration is a prim ary factor in the process and that high concentrations (90%) significa ntly improve the delignification degree. The kinetics of the process w ere satisfactorily explained by a model of consecutive first-order rea ctions corresponding to lignin solubilization followed by lignin conde nsation and reprecipitation onto the lignocellulosic matrix, hydrolysi s of alpha-aryl ether bonds being the dominant reaction of the deligni fication process. The selectivity of the lignin dissolution was practi cally independent of operating conditions. When the degree of delignif ication reached a value around 90% the selectivity decreased considera bly due to lignin condensation. (C) 1997 Elsevier Science Ltd.