THE CHEMISTRY OF ORGANOSOLV DELIGNIFICATION

Probable mechanisms of delignification in the major organosolv pulping systems are reviewed The emphasis is on acidic systems, which least r esemble conventional pulping, although alkaline systems are also exami ned Cleavage of ether linkages is a major factor in lignin breakdown. Under acidic conditions, this is particularly true for alpha-ethers, b ut beta-ether cleavage also plays a role, especially in hardwood pulpi ng. In alkaline systems, the cleavage of beta-ethers is more important . Hardwoods delignify more readily than softwoods, primarily the resul t of differences in beta-ether reactivity, alpha-ether concentration, lignin content, and propensity to undergo condensation reactions. Lign in condensation usually involves reactive carbocation or quinone methi de intermediates.