The Role of Hemicellulose in the Delignification of Wood

Abstract

Hemicellulose was selectively removed from white birch by treatment with cold alkali. Untreated and alkali-treated samples were pulped to various stages of delignification by the acid chlorite process. The acid chlorite reagent was shown to be selective for lignin removal from both samples during the first 60% of delignification.In alkali-treated white birch, the median pore width increased considerably as acid chlorite delignification proceeded. In contrast, in untreated white birch, this parameter remained relatively constant during the first 60% of delignification.Alkali-treated white birch delignified at a much faster rate than untreated white birch. In addition, there was a topochemical preference for removal of lignin from the secondary wall of the fibers in the hemicellulose-deficient wood. Apparently, prior removal of hemicellulose caused larger pores to be produced in the fiber walls during pulping, thereby facilitating a more rapid removal of lignin.