Study On The Dissolution Law Of Bagasse Components Treated With Low Temperature Alkali And Its Black Liquor Circulating Oxygen-alkali Pulpin

China is lack of forest resource,so wood supply for papermaking is heavily dependent on imports.On one hand,the domestic demand for paper and paperboard is increasingly augmented,reasonable making good use of non-wood resource will be the key to solve these problems,as long as the defects of non-timber resources in pulping and papermaking can be reduced and even overcome.On the other hand,it is hard to imagine how long energy and energy chemicals from non-renewable resources would hold out because of excessive exploitation and utilization of them.Biomass,as renewable resource,is better able to replace fossil fuels for its inexhaustiblecharacteristic.The exploitation and use of biomass energy as well as bio-based chemicals has become the inevitable way to achieve sustainable development.To get hemicelluloses as an important biomass conveniently,this dissertation attempts to extract xylan through alkali soaking of bagasse at low temperature.Single factor and orthogonal experiments,involved in alkali concentration,soaking temperature and time,were performed to dissolve out as much xylan as possible,refrain from lignin dissolution to some extent at low temperature,and the maximum dissolubility ratio of pentosan to lignin has been taken as the optimal condition.The best condition is that depithing bagasse was pretreated in 7.5%NaOH aqueous solution at 35℃ for 6 days,resulting in the dissolution of 71.5%pentosan and 73.9%lignin.The residual showed 79.8%of nitric acid ethanol cellulose content and 56.3%of yield.For the soaked residue,SEM image showed rough surface after treated with alkali.Its cellulose crystallinity rose from 53.92%to 59.23%,and the thermal stability increased.Besides,xylose ratio in it was greatly decrease,on the contrary,glucose content was elevated.The element analysis showed that carbon element content in it had no obvious change,while the percentage of oxygen element was increased.Bagasse has been sequentially soaked using alkali at the optimal condition.The precipitations were quantitatively obtained from the black liquor adjusted to different pH value with sulfuric acid solution.Quantitative and qualitative analysis of the precipitates were performed with FT-IR spectra,element analysis,GPC,TGA and HPLC.The hemicelllulose was firstly to precipitated,and the precipitation amount of lignin was increased with lower pH value.Gel permeation chromatography showed that molecular weight of the precipitates changed regularly,i.e.,the lower pH value,the lower the molecular weight,and the worse its thermal stability.Liquid chromatography analysis gave xylose and acid insoluble lignin contents in the precipitates.Bagasse was soaked by means of recycling of the black liquor with comlementary alkali,then pulped with alkali-oxygen.It is indicated that the precipitations obtained from the recycled black liquor were proven to be macromolecular pentosan and lignin-carbohydrate complexes by FT-IR.With the increase of cycling times,the deep veins on the soaked bagasse were gradually covered by sediment.Meanwhile,the viscosity of the soaked black liquor increased first,and then remained approximately constant.Alkali-oxygen pulping of the bagasse soaked with the recycled black liquor gave rise to good pulp properties just by suitable prolonging the preservation time during cooking with the recycle times.Therefore,it is feasible to gain the majority of xylan from the bagasse through alkali soaking at low temperature,prior to its alkali-oxygen pulping.