The Chemical Barrier for Oxygen Delignification

摘要

Softwood kraft pulps with different kappa numbers were oxygen-delignified using different selectivityrnenhancing agents, namely, MgSO_4, phenol, MgSO_4/Phenol, and 3-Methoxyl hydroxyl quinone to examinerndelignification selectivity. The results showed that there is a synergistic effect between MgSO_4 and phenolrnduring oxygen delignification. This effect is more obvious for high lignin content pulp than that for lowrnlignin content pulp. However, examination of the carboxyl groups on pulp fibers along with the carbonaterncontent in the effluent liquors demonstrated that the kappa number of softwood kraft pulp can not droprnbelow 7 without incurring severe cellulose degradation during oxygen delignification despite thernapplication of selectivity enhancement agents.