Pulping with Anthraquinone: Fundamental Chemistry, 1996 Pulping Conference Proceedings
Donald R. Dimmel
Institute of Paper Science and Technology
A review of the collective evidence for the mecha-nism of action of anthraquinone (AQ) in alkaline pulping systems indicates that a unique set of reac-tions is governing the chemistry. AQ and its re-duced forms, anthrahydroquinone dianion (AHQ -2 ) and radical anion (AHQ • ), are mediating reactions in which electrons are transferred from carbohydrates to lignin, causing the former to be oxidized to rela-tively stable aldonic acid polymer end units, and the latter to be reduced, leading to fragmentation and solubilization. The two effects account for the ob-served improved pulp yields and faster pulping rates. Experiments indicate that single electron transfer (SET) reactions are more efficient than nu-cleophilic reactions (soda/kraft systems) in breaking down lignin. The chemistry of AQ, soda, and kraft pulping will be reviewed and evidence for SET reactions presented.
Pulping with Anthraquinone: Fundamental Chemistry, 1996 Pulping Conference Proceedings