Bleaching Miscanthus x giganteus Acetosolv pulps with hydrogen peroxide/acetic acid. Part 2: Behaviour in acetic acid media

摘要

Miscanthus x giganteus bark samples subjected to fractionation by Acetosolv process under optimal conditions were bleached using hydrogen peroxide in acetic acid medium. The influences of the main operational variables in the bleaching of Acetosolv pulps of M.xgiganteus (i.e. hydrogen peroxide concentration (1,6-8,4%), temperature (48,2-81,8°C) and pH (1,8-5,2), have been assessed on pulp yield, kappa number, viscosity, saponifiable groups and brightness of pulps. In order to identify the optimum operating conditions, a rotatable and orthogonal second-order factorial design of experiments was used. Results from the fitting experimen- tal data to empirical mathematical models demonstrate that in general the delignification was extensive, and pulps can achieved with kappa number below 15. The chemical composition and properties of the bleached pulps fulfilled the requirements for forthcoming bleaching stages. Moreover, the use of chelating agents in the hydrogen peroxide stage along with the study of pH and time effects outside limits of the experimental design was studied.