Reactivity of Lignin Diphenylmethane Model Dimers Under Alkaline Pulping Conditions

The reactivity of a series of phenolic lignin diphenylmethane (DPM) model dimers has been examined in soda and kraft cooks, in an attempt to understand the role of lignin condensation in the alkaline delignification process. These condensed dimers were shown to be rather stable in alkali in the absence of O2 even at elevated temperatures. In contrast, they were sensitive to traces of O2 present in air, and the degradation mechanism involved was shown to be different from that occurring under mild alkali-O2 conditions.