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离子液体预处理纤维素直接转化制山梨醇
高凯
Subtype硕士
Thesis Advisor周清
2018-07
Degree Grantor中国科学院研究生院
Degree Name硕士
Degree Discipline化学工程
Keyword微晶纤维素,山梨醇,离子液体,预处理,水解加氢
Abstract

山梨醇是一种具有广泛用途的大宗工业化学品,被美国能源部筛选为十二种最具应用前景的生物基平台化合物之一。工业上通过葡萄糖加氢制备山梨醇,该生产工艺所需的原料葡萄糖价格昂贵,使山梨醇生产成本高,因此采用价格低廉的原料生产山梨醇显得尤为重要。纤维素是一种价格便宜的生物质资源,将其作为原料应用于山梨醇的生产具有重要经济意义。但是直接转化纤维素制山梨醇至今仍存在难点,主要原因是纤维素结构中存在复杂的氢键网络结构,使得纤维素难以被定向高效降解为小分子糖,导致后续催化转化反应中山梨醇产率及选择性较低。本文针对如何破坏纤维素分子内氢键网络结构,促进纤维素转化制山梨醇反应过程开展研究,主要研究内容和成果如下:(1)采用球磨和离子液体溶解相结合的方法对纤维素进行预处理。经过4 h球磨后,纤维素的结晶度由最初的79.9%急剧减少至3.2%,表明纤维素中结晶区域面积显著减少,其分子内氢键网络结构被破坏。将球磨后的纤维素溶解在[Amim]Cl中,离子液体中阴阳离子分别与纤维素分子内脱水葡萄糖中羟基的氢氧原子相结合,进一步破坏纤维素分子内的氢键结构网络。此外,将纤维素溶解在离子液体中可以使不溶于水的固态纤维素转变成液体形态的离子型纤维素溶液,增大纤维素与催化剂之间的接触面积,降低纤维素水解反应的难度。(2)分别对纤维素水解和葡萄糖加氢反应开展研究。在纤维素水解反应中,固体酸Nafion NR50具有强酸性,它可以有效的促进纤维素水解,水解产物葡萄糖的产率为55.2%;在葡萄糖加氢反应中,Ru/AC的大粒径分布可以高效的促进葡萄糖加氢转化为山梨醇,在其催化作用下,葡萄糖的转化率可达100%,山梨醇的产率高达96.1%。(3)研究纤维素直接转化制山梨醇的反应。在Nafion NR50和Ru/AC的催化作用下,球磨后溶解在[Amim]Cl离子液体中的纤维素通过水解加氢反应可以直接转化成山梨醇,150 ℃下反应1 h后,山梨醇产率可达34.3%。本研究提出了一种由纤维素直接转化制山梨醇的新工艺,也拓展了离子液体在生物质转化为平台化合物方面的应用。;Sorbitol is a large industrial commodity with a wide range of applications. The Department of Energy (DOE, USA) has screened it as one of the twelve most promising bio-based platform compounds. The production of sorbitol in industry is mainly through glucose hydrogenation. The production cost of sorbitol is extremely high because of the high cost of glucose. Therefore, it is very important to reduce the production cost of sorbitol. Cellulose is a widely distributed and cheap biomass resource. It is of great economic importance to use cellulose as raw material in sorbitol production. However, there are still difficulties in the direct conversion of cellulose to sorbitol. The main reason is that there is a complex hydrogen bond network structure in the cellulose structure, which makes the cellulose difficult to be degraded efficiently and resulting in the subsequent catalytic conversion of low yield and selectivity of sorbitol. This study focuses on the disruption of hydrogen bond network structure in cellulose molecules in order to promote the conversion of cellulose to sorbitol. The main research contents and achievements are as follows:(1)Pretreatment of cellulose by ball milling and ionic liquid dissolution. After 4 h ball milling, the crystallinity of cellulose decreased sharply from the initial 79.9% to 3.2%, indicating that the area of the crystalline region of cellulose decreased significantly, and the structure of the intramolecular hydrogen bond network was destroyed. The cellulose after ball milling is dissolved in [Amim]Cl, and the anions and cations in the ionic liquid are combined with hydrogen and oxygen atoms in the hydroxyl groups of dehydrated glucose in the cellulose molecule. The combination of ionic liquid and hydroxyl group further destroys the hydrogen bond structure network in the cellulose molecule. In addition, the dissolving of cellulose in the ionic liquid can transform the insoluble solid cellulose into a liquid form of ionic cellulose solution, which increase the contact area between the cellulose and the catalyst, and reduce the difficulty of the cellulose hydrolysis reaction.(2)Cellulose hydrolysis and glucose hydrogenation were studied respectively. In the reaction of cellulose hydrolysis, based on the strong acidity of solid acid Nafion NR50, it can effectively promote the hydrolysis of cellulose, and the yield of glucose can reach up to 55.2%. In the reaction of glucose hydrogenation, the large particle size distribution of Ru/AC can effectively promote the conversion of glucose to sorbitol. With the catalysis of Ru/AC, the glucose conversion can reach 100%, and the yield of sorbitol as high as 96.1%.(3)The study on the direct conversion of cellulose to sorbitol. With the catalysis of Nafion NR50 and Ru/AC, the ball-milled cellulose which is dissolved in the [Amim]Cl can be converted into sorbitol by hydrolytic hydrogenation. The yield of sorbitol can reach 34.3% after 1 h reaction under 150 °C.In this study, a new production process of sorbitol was proposed from microcrystalline cellulose, and this research also expanded the application of ionic liquids in biomass conversion to platform compounds. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26872
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
高凯. 离子液体预处理纤维素直接转化制山梨醇[D]. 中国科学院研究生院,2018.
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