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桉木RDH蒸煮过程中木质素与碳水化合物的溶出规律研究

DISSOLVATION RULES OF LIGNIN AND CARBOHYDRATES DURING RDH KRAFT PULPING OF EUCALYPTUS WOOD

  • 摘要: 对桉木常规硫酸盐(KP)法和快速置换加热(RDH)硫酸盐法蒸煮过程中,木质素与碳水化合物中各单糖组分(葡萄糖、木糖、甘露糖和阿拉伯糖)的溶出规律进行了研究,分析了常规KP浆和RDH浆在纤维素结晶度和α-纤维素含量上的差异。与常规KP法蒸煮相比,在RDH蒸煮的初期,木质素和碳水化合物各单糖组分就大量溶出,蒸煮时没有表现出明显的初始脱木质素阶段。蒸煮结束后,RDH浆比常规KP浆具有相对较高的葡萄糖(纤维素)含量和相对较低的木糖、阿拉伯糖和甘露糖(半纤维素)含量。RDH纸浆的α-纤维素含量相对较高,但纸浆的纤维素结晶度与常规KP浆相比并没有明显的不同。

     

    Abstract: Dissolving rules of lignin and carbohydrates(e.g.glucose,xylose,mannose,arabinose) during rapid displacement heating(RDH) kraft cooking for eucalyptus wood were investigated.Difference of cellulose crystallinity and α-cellulose content of pulps produced by conventional kraft cooking and RDH cooking were also studied.It was (observed) that delignification course during RDH pulping was divided into two phases:bulk phase and residual phase.As compared with conventional kraft pulping,the initial phase of delignification did not obviously occur during RDH pulping,and lignin was rapidly degradated and dissolved in the early period of RDH cooking.The dissolving rates of carbohydrates in the early period of RDH pulping were higher than that of conventional kraft pulping.Glucosidic component was rapidly dissolved in warm black liquor(WBL) stage and hot black liquor(HBL) stage of RDH cooking,but was slightly dissolved after HBL stage.Xylose 44.92%,mannose 33.46% and arabinose 49.09% have been dissolved in WBL and HBL stages of RDH process.After HBL stage,dissolving rates of xylose,arabinose and mannose decreased.As compared with conventional kraft pulps,RDH pulps have relatively high glucose(cellulose) content and relatively low xylose,arabinose and mannose(hemicellulose) content.The α-cellulose content of RDH pulp was a little higher than that of conventional kraft pulp.However,differences of cooking methods and cooking conditions have no significant effect on cellulose crystallinity.

     

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