Process Research On Separation And Conversion Of Bamboo Components

Bamboo resource is considered as a candidate feedstock of bio-based materials and energy for its high growth efficiency, if we can achieve efficient separation of three components, it will significantly increase the value of bamboo. In this study, bamboo was used as raw materials, the integrated process of hydrothermal method and ionic liquid-ethanol-water system was designed. Hydrothermal pretreatment was used to selectively stripping hemicellulose fraction in bamboo, of which the process conditions was investigated. Subsequently, the dissolution law of hydrolysis residue in ionic liquid-ethanol-water system and the physicochemical properties of products were fully analyzed. We carried out a preliminary conversion of cellulose into fermentable sugars and lignin into phenolic compounds. This integrated process made the efficient separation and conversion of bamboo components achieved, and it has the advantages of environmentally friendly, no corrosion to equipment and recycle of solvent, possesses certain application prospect in fractionation and conversion of bamboo.Bamboo hemicellulose was selective stripped by hydrothermal pretreatment. The optimum conditions were concluded as follows: temperature 170℃, reaction time 60 min, solid-liquid ratio 1:12 g/m L. A large amount of hemicellulose was destroyed and degraded during pretreatment, but almost no degradation of cellulose and lignin. The removal rate of hemicellulose was 82.88% and the retention rate of cellulose was 97.39%. The main structure of bamboo water-soluble hemicellulose is xylan, which is linked with arabinose and glucuronic acid as side chain. Hemicellulose products have high purity with substantially free of lignin.Bamboo hydrolysis residue dissolved in ionic liquid-ethanol-water system and lignin was extracted. The optimal dissolution conditions were as follows: temperature 170 ℃, reaction time 4 h, [AMIM]OAc:C2H6O:H2O?5:5:0.5(v/v/v). Under this condition, the dissolution rate was 43.14%, the purity of crude cellulose and crude lignin products were 91.38% and 87.70% respectively, and recovery rate of cellulose and lignin were 92.07% and 87.43 %. The treatment of ionic liquid-ethanol-water system successfully broke the hydrogen bond network between cellulose and lignin, which make a large number of lignin dissolved, and obtain high purity of cellulose samples. In addition, part of the crystal structure of bamboo cellulose was destroyed, if it is used for enzymatic and fermentation, it can achieve higher enzymatic saccharification rate and yield. Bamboo lignin is a typical GSH lignin, lignin product contains more syringin(S) unit.In the same conditions for enzymatic hydrolysis, the substrate pretreated by the integrated process achieved the highest saccharification rate of 82.87%, which was 2.66, 1.97, 1.44 times of the untreated bamboo and the only one step pretreated substrate(the hydrothermal method or ionic liquid-ethanol-water system), respectively. This shows that the integrated process could remove more hemicellulose and lignin, obtain a substrate which is more susceptible to enzymatic hydrolysis, thereby increasing the yield of fermentable sugars. The mild hydrogenation depolymerization of lignin product was carried out, short chain phenolic compounds can be obtained. Further optimized the conditions, there is expection to selectively produce high value-added chemicals phenols.