Acetosolv delignification of Miscanthus sinensis bark : Influence of process variables

Abstract

Using a face-centred composite experimental design with three central point replicates, we investigated the effects of cooking time (60–180 min), acetic acid concentration (60–95% of liquor weight) and HCl concentration (0.05–0.15% of liquor weight) on the yield, residual Klason lignin content and total polysaccharide content of pulps obtained from Miscanthus sinensis bark by the acetosolv process. Response surfaces fitted satisfactorily to the experimental results showed the most influential of the independent variables to be acetic acid concentration; increasing acetic acid concentration reduced yield and lignin content, and increased total polysaccharide content (except at the highest concentrations of the acids). The response surface for lignin content was used to design a Box–Wilson steepest-descent optimisation procedure to determine the conditions minimising pulp lignin content; the minimum achieved, 0.5%, was obtained using a cooking time of 147 min, an acetic acid concentration of 93.25% and an HCl concentration of 0.122%, under which conditions pulp yield was 52.6%.