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In an effort to augment the efficiency of an oxygen delignification stage, we examined the effectiveness of various heterocyclic aromatic nitrogen compounds as possible activators of such a stage. It was shown that a variety of such compounds may act as activators in the presence of hydrogen peroxide, improving the delignification efficiency of oxygen delignification. Among the group of activators examined, 1,10-phenanthroline was found to be the most potent. Injecting the activator in the middle of the delignification stage (simulating a two-stage process) was shown to provide most of the benefits. The optimum injection time was found to at 30 min from the onset of the delignification. At the optimal charge of 1,10-phenanthroline (0.3%), the delignification was improved by 18%. While the presence of copper ions was found to further improve the efficiency of the activating system, this was accompanied by an extensive carbohydrate degradation.

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