Influence of Lignins on the Degradation of Cellulose During Ozone Treatment

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Abstract
Three lignin-carbohydrate model systems were studied to determine the mechanism of the effect of lignin on cellulose degradation during ozone bleaching. The three model systems are: methyl β-D-glucopyranoside, dextran and fully-bleached kraft pulps in the presence of various lignin model compounds. It was found that the lignin models can both promote and suppress the degradation of the carbohydrate during ozone treatment. The presence of the lignin models can exhibit a protective effect by competing with the carbohydrates for the ozone available in the system. On the other hand, the ozone-lignin reactions give rise to the formation of hydroxyl radicals which promote the carbohydrate degradation. It is suggested that much more hydroxyl radicals are formed via the ozone-lignin reaction route than via ozone self-decomposition. Among the lignin model compounds studied, the phenolic lignin structures have a more pronounced effect on carbohydrate degradation. This is explained by the easier formation of hydroxyl radicals from phenolic lignin models than from non-phenolic models.

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