Abstract
The protective effect of anthraquinone (AQ) on wood carbohydrates during alkaline pulping of spruce sawdust (25% NaOH, 170°C, ratio solid-liquid 1:100, 1% AQ) and the 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/1, 170°C, 1h, ratio solid-liquid 1:20, AQ 0.016 mol/1) has been investigated. The stabilizing effect of AQ on carbohydrate redox end groups in the above mentioned media is shown on cellobiose an example. The lower content of aliphatic acids in the black 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 allows 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 carbohydrate chains in all investigated media and that this effect is greater in the solvents with the highest basicity.
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