Relationship Between Delignification and Dissolution of Carbohydrates in the Digestion of Birchwood

Abstract

Birchwood digestion with cooking liquor of bicomponent, SO₂-MgSO₄, or of Mg-base sulfite was carried out by using a meal of 40-80 mesh which was extracted with ethanol-benzene, and then each cooking reaction was analyzed in the same manner as that used in the previous digestion of sprucewood.
From the kinetic studies, differences in the rate of the reaction and in the relationship among the reactions were found and discussed the relation between the two liquor systems. In the digestion of birchwood, the dissolution of carbohydrates showed a marked influence on the rate of reactions of lignin, i.e., delignification and sulfonation, as was found in the sprucewood digestion. This suggested that the dissolution of carbohydrates would accelerate the development of porous structure in a wood cell wall, and concomitantly, would contribute to an increase in reactivity of lignin.
Furthermore, some interesting differences between the two wood species were detected when their digestions were compared. This would be ascribed to more intimate cell-tissue in hardwood than that in softwood.