Pulp Properties Influencing Oxygen Delignification Bleachability, 1999 Pulping Conference Proceedings

Michael Zawadzki & Arthur Ragauskas

Institute of Paper Science and Technology

The influence of peracetic acid pretreatment and interstage treatment on subsequent oxygen delignification was evaluated for both kappa 24 and 47 softwood kraft pulps. Both pulps were oxygen delignified under standard (~ 42% delig.) and aggressive (~ 68% delig.) conditions. Selected pulps were also pretreated with distilled peracetic acid under slightly alkaline conditions (pH = 8). Peracetic acid pretreatment was found to increase the efficiency of the oxygen delignification stage with no loss of pulp viscosity. A kappa 47 pulp could be oxygen delignified under aggressive conditions to give a pulp of comparable viscosity and brightness as standard oxygen delignified kappa 24 pulp. The fundamental chemistry of the process was studied by 1 H–, 13 C–, 19 F–, and 31 P–NMR spectroscopy. Residual lignin quinone contents were quantified by trimethylphosphite/31 P–NMR and 19 F–NMR spectroscopy. Oxygen delignification conditions were found to have little influence on the introduction of colored quinone and carbonyl structures. Condensed diarylmethane and carboxylic acid lignin structures were enriched and/or formed, particularly under aggressive oxygen conditions.