Studies on Water Solubilization of Lignin (1)

Studies on Lignin No. 110

Abstract

In order to develop a new process for the preparation of a water soluble kraft lignin, sulfonation mechanism of lignin model compounds by oxidizing reagents-sulfite system and its applicability to the sulfonation of kraft lignin were investigated. Among the lignin structural units, a catecholic structure was turned out to be most reactive to this sulfonation reaction. A guaiacyl structure without α-carbonyl group showed much higher reactivity than that of a guaiacyl structure withα-carbonyl group. Kraft lignin was totally water solubilized by this sulfonation reaction, regardless the kind of oxidizing reagent, such as MnO₂, KMnO₄, K₂Cr₂O₇ and K₃Fe (CN) ₆.