不同方法预提取玉米秆半纤维素及其对后续制浆漂白的影响

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

分别采用KOH和NaOH溶液在4种条件下对玉米秆中半纤维素进行了预提取,利用离子色谱检测了提取液中半纤维素的糖类组分及含量。剩余原料用NaOH-AQ法制浆并将浆料进行漂白。结果表明,碱法提取玉米秆半纤维素效果显著,在提取温度为75℃,提取时间为2 h,KOH提取液浓度为1.5 mol/L时,半纤维素提取率可达99%。碱法水解之前以55℃热水处理对半纤维素的溶出并无显著作用。在温度75℃、提取时间2 h时,相同OH-浓度的KOH溶液对半纤维素的提取率比NaOH溶液高20.5%。制浆漂白结果表明,预提取可使浆料卡伯值下降,显著提高未漂浆的白度,各提取条件下NaOH-AQ浆的得率无明显差别,均比未处理的NaOH-AQ浆得率下降10%左右。无论是未漂浆还是漂白浆,碱法预提取均可使浆料撕裂指数显著提高,但其他物理强度有所降低。

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.