The effect of anthraquinone on wood carbohydrates during alkaline pulping in aqueous organic solvents

摘要

The protective effect of anthrauinone (AQ) on wood carbohydrates dring alkaline pulping of spruce sawdust (25percent NaOH, 170 deg C, ratio solid-liquid 1:100, 1percent AQ) and samples of kraft pulp in water and aqueous organic solvents: water-EtOH (1:1), water-MeOH (1:1), water-dioxan (7:3), water-DMSO (7:3), (NaOH 1.25 mol/l, 170 deg C, 1h, ratio solid-liquid 1:20, AQ 0.016 mol/l) has been investigated. The stabilizing effect of AQ on carbonhydrate redox end groups in the above mentioned media is shown on cellobiose an example. the lower content of aliphatic acids in the block liquor and the higher yield of the wood residue (at the same degree of delignification) after cooking of spruce sawdust and kraft pulp with the addition of AQ was established. It allwos confirmation that the prevention of "peeling" reactions by oxidation of aldehyde groups up to carboxyl ones occurs in the presence of AQ more extensively than in its absence. At the same time the decrease of the degree of polymerisation (DP) in nondissolved samples of kraft pulp after treatment indicates that AQ promotes the alkaline solvolysis at arbitrary sites of carbhydrate chains in all investigated media and that this effect is greater int he solvents with the highest basicity.