OXYGEN DELIGNIFICATION IN A WATER PLUS ORGANIC-SOLVENT SOLUTION .1. DELIGNIFICATION OF POPLAR CHIPS (POPULUS SPECIES) IN A WATER-ACETONE SOLUTION

Oxygen delignification of Eucalyptus globulus wood in ethanol/water solutions (50/50, V/V) and of cottonwood in acetone/water solutions (60/40, V/V) lead to different results: particularly, delignification kinetics are very different. In both cases, experimental pulping conditions (partial pressure of oxygen, temperature of delignification, liquor-to-wood ratio) and aqueous organic solutions properties (molar composition, dielectric constant, oxygen and lignin solubility) are identical. The study of the main reaction parameters (temperature, partial pressure of oxygen, time pulping) shows that they have different influences on the delignification of the two different woods. This different behaviour is explained in terms of structure and porosity of the two different species of wood. Porosimetric studies show that eucalyptus wood has a very high amount of weak diameter pores and a specific area that is higher than that of poplar wood.