Simulation of Lignin Degradation During Chlorine Dioxide Delignification Stage

The chlorine dioxide reaction with residual lignin of chemical pulp during delignification stage was simulated using phenolic and non-phenolic lignin model compounds applying various amounts of chlorine dioxide. Based on the reaction of model compounds and measurement of inorganic chlorinated species, three reaction phases were established for degradation of lignin model compounds. It was found that after the degradation of free phenolic units, the reaction of primary oxidized products by ClO2 competed with the oxidation of non-phenolic aromatic structure. The results obtained by lignin model compounds were compared with the pulp delignification results. This comparison indicated two special phases for the reduction of the kappa number. The initial phase corresponded to the oxidation of phenolic units without secondary reactions. The second phase corresponded to the oxidation of the non-phenolic units in competing with secondary reactions. The results of this confirmed the over consumption of chlorine dioxide by primary oxidized lignin in the secondary reactions.