Pre-extraction of hemicelluloses and subsequent ASA and ASAM pulping: Comparison of autohydrolysis and alkaline extraction

Commercial aspen wood chips were treated with hot water (autohydrolysis) and with alkali to extract part of the hemicelluloses. The extracted residues and an unextracted wood (control) were subjected to pulping based on the alkaline sulfite anthraquinone (ASA) and alkaline sulfite anthraquinone methanol (ASAM) methods to afford pulps useful for paper production with the same degree of delignification. Unlike the autohydrolysis residue, the alkali extracted residue was shown to favor subsequent pulping in terms of pulping yield, charges of chemicals, cooking times and properties of pulps. The experimental conditions and results are discussed.