Understanding Contributing Factors to a Low Oxygen Delignification for Hardwood Pulps

The O{2} delignification pattern of aspen kraft pulps has been shown distinctly different from that of the pine pulp based on a reduction in the apparent pulp kappa number. This phenomenon can be attributed considerably to their variations in the residual extractive and hexeneuronic acid (HexA) unit content, as they interfered with the lignin determination methods. However, after a correction for contributions from these non-lignin components, the hardwood kraft pulps still displayed a lower response to the O{2} delignification than the pine pulps. Thus, the reactivity of residual lignin is a significant factor affecting the relative performance of hardwood and softwood pulps in O{2} delignification.