Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures

摘要

The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21-70 deg. C, using a UV-spectropho- tometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissoci- ation was decreasing when the temperature was elevated. Dissociation curves and apparent pK_0 values were also calculated for the polydisperse sample at the same conditions, using he van't Hoff and the Poisson-Boltzmann equations.