Comparative Study of Corn Stover Hemicellulose Pre-extraction Methods and Their Effects on Subsequent Pulping and Bleaching

Potassium hydroxide(KOH) and sodium hydroxide(NaOH) were used for pre-extraction of corn stover hemicellulose under four conditions,the composition of the hemicellulose polysaccharides in the extracts and their corresponding contents were analyzed by ion chromatography.After pre-extraction,the residues were experienced NaOH-AQ pulping and QP bleaching.Results indicated that alkaline extraction had significant effect on corn stover hemicellulse extraction,when extraction temperature was 75℃,extraction time was 2 h and the extraction liquor was 1.5 mol/L KOH,extraction yield of hemicellulose reached 99%.55℃ hot water treatment before alkali hydrolysis had little effect on hemicellulose dissolving.When extraction temperature was 75℃ and extraction time was 2 h,yield of hemicelluose extracted with KOH was 20.5% higher than that with NaOH at the same OH-concentration.Results of pulping and bleaching experiments of the extracted residues showed that Kappa number of the pulp decreased and brightness of the unbleached pulp was much higher compared with the pulp from the raw materials without extraction,the yields of NaOH-AQ pulps were almost the same when different extraction methods were used,about 10% lower than that of the pulp from material without extraction.Tear index of both bleached and unbleached pulp from the extracted material increased greatly,while other physical properties such as density,breaking length and burst index decreased.