Organic Acid Pulping of Wood - Part II. Acetic Acid Pulping of Aspen

Aspen chips were cooked in aqueous acetic acid (50—87.5%) for up to two hours at temperatures in the range of 160-185PC. Good delignification was achieved (Kappa numbers 10-40) with pulp yields of50—60%. Although satisfactory lignin removal could be realized with as low as 50% acetic acid, the de-lignification selectivity was improved at higher concentrations. A useful guideline for Optimum choice of the acetic acid concentration in the liquor is a Hildebrand solubility parameter of approximately 11.0. An acetone wash may be necessary to remove reprecipitated lignin after the cook. The pulps showed satisfactory to good water absorbency.