Summary
The kinetics of delignification of a kraft-AQ southern pine pulp with hydrogen peroxide catalyzed by
[LMn(IV)(μ-O)3Mn(IV)](ClO4)2 (1), where L = 1,2-bis(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethane
was studied. The degree of delignification was significantly improved by using the catalyst. The pulp
was bleached for 2 hours at 80°C, in 10% consistency with 2% NaOH, 4% H2O2 and 60 ppm catalyst
charges on pulp (O.D.). Kappa number of the pulp was reduced from 31.6 to 16.8 corresponding to a
degree of delignification of approximately 4%, while GE brightness was increased from 24.2 to 44.7.
At the same time, viscosity of the resulting pulp was reduced from 31.1 mPa•s to 20.1 mPa•s compared
to the reduction from 31.1 mPa•s to 20.1 mPa•s in the uncatalyzed bleaching under the same reaction
condition. This indicates that the degradation of the carbohydrates was moderate in the catalyzed bleaching
compared to the uncatalyzed bleaching. The delignification was found to follow pseudo first order
kinetics with respect to kappa number, i.e., residual lignin, in the initial phase and quickly slowed down
after 30 minutes (residual phase) under all the reaction temperatures investigated. The delignification
rate constants in the initial phase were 0.17, 0.18, and 0.21 min−1 at 50, 60, and 80°C, respectively.
Degree of delignification at the delignification time of 30 minutes is approximately 40% at 80°C. The
possible delignification mechanism was discussed on the basis of the kinetic studies and lignin model
compound experiments.
Production of dissolving grade pulp from tobacco stalk through SO2-ethanol-water fractionation, alkaline extraction, and bleaching processes
