Reactions of Lignin during High-Yield Pulp Bleaching

Abstract

In the bleaching of high yield pulp, it is necessary to degrade selectively the chromophoric group in pulp components, lignin, carbohydrate and extractives. The word of “selective” used here means that there is no degradation or dissolution of colorless materials during bleaching. Numerous papers have been published regarding the mechanism of high yield pulp bleaching, but many important problems have yet to be dealt with.
The objective of this review is to clarify the reactions of lignin during the course of hydrogen peroxide and dithionite bleaching from the standpoint of lignin chemistry. Changes in the number of functional groups in lignin preparations were measured after hydrogen peroxide and dithionite bleaching. Lignin model compounds were reacted with these bleaching reagents and the reaction mechanism were discussed.