| In fact, formic acid pulping was to separate cellulose, hemicellulose and lignin from raw materials. After separation, the cellulose was solid existing the cooking system while lignin and hemicellulose were dissolved into black liquor.The products of pulp for paper and other chemical industry,and the dissolved hemicelluloses have demonstrated to be a potential feedstock in production of xylitol,furfural and additives et al, and lignin was utilized for lignin composites and raw material for chemicals. Furthmore, it can obtain promising profits as well as avoid pollution when total utilization of those by-products, thus it was important to isolate and purify those products in black liquor.In this experiment, it was to investigate the effect of the formic acid pulping condition on process of pulp cooking and the rule of lignin dissolved in ultrastructures of wheat straw cell walls,and then to provided schedule to isolation lignin and carbohydrates from black liquid and to grade carbohydrate in membrane separation. Cooking condition was found from researching the wheat straw formic acid cooking and by-products extracted.It was found that:in order to get pulp the cooking time was less then 120min and the yield of pulp decreased and carbohydrate degrade when cooking time prolonged;in the first cooking period, it was showed that delignification happened homogeneously in cell wall, and then lignin in CC was deligninfied more rapidly.and in CML.; extracting hemicelluloses first can gain better results,.The increasing rate of yield of lignin reached maximum when pH was set at 2.5. The isolation carbohydrate product would contains some lignin when prcecipitated with ethanol. The isolated carbohydrates consisted of xylo (75%),,Ara(10%) and Glu 9% and et al. Tha desperity of carbohydrate Mw was broad,after long time cooking the Mw decreased meanwhile the desperity become small.It was provided some theory for improving the utilization rate of raw materials and by-products of further usage...
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