【作者】 黄耀兵；

【导师】 郭庆祥；

【作者基本信息】 中国科学技术大学 ， 有机化学， 2014， 博士

【摘要】 由于化石资源的大规模使用,随之引起的全球变暖、大气污染和能源危机等问题已经成为全世界关注的焦点。发展绿色可再生能源是未来发展的主要方向。生物质作为一类重要的可再生资源,其巨大应用潜力已经开始显现。从生物质资源制备化学品或者燃料已经成为各国解决能源危机的一个重要途径。其中,木质纤维素基生物质由于其产量大分布广等特点受到广泛关注,其发展和利用不仅解决了生物能源与人争粮,与粮争地的问题,还体现了“变废为宝”和环境保护等发展意识。目前,木质纤维素类原料通过水解途径可以高选择性地获得可溶性的糖类分子,进而可以转化成为用途广泛的平台分子,如5-羟甲基糠醛和乙酰丙酸等。再以这些平台分子为原料,通过基元反应的转化可以制备更多高附加值化学品,以丰富生物质基化学品产品库。平台分子5-羟甲基糠醛和乙酰丙酸等分子,可以通过不同基元反应制备平台分子下游化学品(毗咯烷酮,脱羰产品)和液体燃料(Y-戊内酯,2,5-二甲基呋喃和长链烷烃等)。但是目前这些转化还存在诸多待解决的问题,如催化中心金属昂贵、反应条件苛刻、产物选择性差,催化体系过于复杂和反应机理不明等。因此,发展更多高效温和催化体系来解决上述问题,为这些基元反应提供新的方法和思路显得尤为必要。基于此,本论文主要发展了多种金属中心催化体系,实现对产物分布的选择性调控,从而获得最优的反应转化参数,实现温和条件下的绿色高效转化过程。论文主要分为以下几个部分：在第1章中,我们主要介绍了目前生物质转化制备燃料的发展状况以及平台分子的概念。接着详细了综述了关于平台化合物中5-羟甲基糠醛和乙酰丙酸两个分子的合成的最新研究进展。同时,介绍了两个平台分子各自转化成为化学品或者燃料分子的最具代表性的研究进展。第2章介绍了乙酰丙酸酯类化合物通过氢转移方法制备γ,-戊内酯。利用高活性的骨架镍催化剂,第一次实现了室温条件下乙酰丙酸酯类到γ-戊内酯的定量转化。反应研究了不同金属中心负载型催化剂在异丙醇溶剂中不同氢转移活性比较。考察了不同一级醇和二级醇类对于氢转移效率的影响。提出了一条从生物质基糠醇、HMF和果糖三种分子一锅两步制备γ-戊内酯路线。第3章介绍了乙酰丙酸和甲酸混合液的还原胺化制备吡咯烷酮的转化过程。反应在无溶剂情况下,将乙酰丙酸、甲酸和胺类混合液在Ru系催化剂和大位阻膦配体催化下,通过原位分解甲酸产生H2,实现了乙酰丙酸和胺类的还原胺化过程,获得了最高94%的吡咯烷酮收率。考虑到糖类水解液是乙酰丙酸和甲酸的混合液,因此还考察了水相条件下不同胺类在催化体系中的兼容性,获得了一批重要的吡咯烷酮分子。最后研究了从真实葡萄糖水解液出发制备吡咯烷酮的转化过程,为生物质碳水化合物制备高附加值化学品吡咯烷酮提供了重要的方法。第4章介绍了平台分子5-羟甲基糠醛选择性脱羰方法。反应使用Pd负载型催化剂,实现了HMF选择性脱除羰基的过程,获得了96%的目标产物产率。反应考察了不同有机溶剂和催化剂载体对于HMF分子的稳定性的影响。同时,研究了不同载体和不同方法制备的Pd催化剂活性。发现分子筛对于反应体系的除水干燥有着重要作用。最后研究了其他生物质基醛类分子的脱羰反应,拓展了反应应用范围。第5章研究了5-羟甲基糠醛氢解制备燃料分子2,5-二甲基呋喃的反应。合成了双功能催化剂Ni-W2C/AC并用于HMF分子的氢解反应,在较为温和的条件下,获得96%的2,5-二甲基呋喃产品产率。对催化剂进行结构表征,进一步了解反应催化活性组分。对反应跟踪和中间体捕捉,发现反应经过5-甲基糠醛中间体,之后再进一步氢解获得DMF。同时,研究了催化剂Ni和W2C颗粒对反应所起作用,发现Ni组分主要实现醛基加氢,而W2C组分主要以Lewis酸作用协助发生氢解反应。第6章研究了生物质基醛类分子经过增碳反应制备高碳液体燃料的转化。反应以五碳糖糠醛为模型物,利用频哪醇偶联反应,在金属还原剂的条件下实现了糠醛自身的增碳偶联,从而获得了C10液体燃料的前体。反应考察了不同还原体系对偶联产物选择性的影响,获得了最高98%的C10偶联产物的产率。同时,考察了六碳糖分子5-甲基糠醛和来源于木质素的芳香醛类分子的增碳反应,获得了相应的C12和C14燃料前体。最后,利用Pt/C和固体酸组合催化剂,实现了这些燃料前体到高碳液体燃料的制备,合成了C10-C14的饱和烷烃分子,为生物质基平台分子制备高碳液体燃料提供了新的思路。第7章对全文进行了总结和展望。综上所述,本文主要以平台分子为研究对象,采用不同催化转化手段实现了平台分子到不同化学品或者燃料分子的绿色转化过程,研究了不同催化剂对于反应活性和选择性的影响规律。通过新催化体系的发展拓展了生物质基平台分子的转化和应用。更多还原

【Abstract】 Due to the massive use of fossil fuels, global warming, air pollution and energy crisis has become an important issue of worldwide concern. The development of green sustainable energy system becomes an important issue in the future. Biomass, nature products from sunlight and CO2, has showed its potential of being renewable resources. Preparation of chemicals and fuels from biomass has become an important way to solve the energy crisis. Due to the large production and wild distribution, lignocellulosic biomass receive a lot of concern in these years, avoiding the previous problems that biofuels from food would compete with people about the food, and compete with food about the land. Besides, the utilization of biomass can also contribute to the environment protection and make the waste into treasure. Currently, lignocellulosic biomass can be converted to soluble sugars by hydrolysis, and subsequently converted into platform molecules, such as5-hydroxymethylfurfural and levulinic acid and so on. These platforms molecules can be transformed into more high value-added chemicals through elementary reactions, which will greatly enriched biomass-based chemicals.The platform molecule5-(hydroxymethyl)furfural (HMF) and levulinic acid (LA) can be converted into different chemicals (pyrrolidone decarbonylation products) and fuels (y-valerolactone,2,5-dimethyl furan and long-chain alkanes) over different catalysts. However, many problems about the conversion are raised, such as the harsh reaction conditions, poor product selectivity, complex reaction systems and reaction mechanism. Thus, it is essential to develop more efficient and mild catalytic system to improve the reaction efficiency and make the conversion greener, offering more choice for the industrial production. Based on this, the main work involeves:In the first chapter, we introduced the current development of biofuels from biomass and the platform molecules derived from biomass. Then, we reviewed the latest development of the preparation methods and representative application examples of platform molecules HMF and LA.In the second chapter, we reported a new catalytic transfor hydrogenation process for the conversion of LA to GVL at room temperature. The use of highly active Raney Ni catalysts led to a quantitative conversion of LA to GVL. Various catalysts and hydrogen sources (primary and secondary alcohols) were evaluated during the reaction. Finally, a one pot two steps reaction from furfuralcohol, HMF and fructose were provided.In the third chapter, we present a new route about the conversion of levulinic acid and formic acid derived from acidic dehydration of biomass-based carbohydrates, to pyrrolidines over different homogeneous ruthenium catalysts with phosphine ligands under mild conditions, achieving a highest94%yield. Various amines were tested in the optimized conditions and got a small library of pyrrolidines with different function groups. The production of pyrrolidines from glucose was carried out on laboratory-scale and achieved34%yield of product.In the forth chapter, we present a selective decarbonylation method of HMF to the corresponding product. Supported Pd catalysts were prepared and achieved a highest96%product yield. The catalysts with different supports and preparation methods gave different performances toward decarbonylation reactions. The stability of HMF was evaluated in the presence of different solvents and supported materials at higher temperatures. Finally, the catalytic system can be successfully applied to other aldehydes derived from biomass, achieving excellent results.In the fifth chapter, We propose a non-noble bimetallic catalyst based on nickel-tungsten carbide for the conversion of the platform molecules5-(hydroxymethyl)furfural into the liquidfuel molecule2,5-dimethylfuran (DMF). Different catalysts, metal ratios and reaction conditions have been tested and give rise to a96%yield of DMF. The catalysts have been characterized and are discussed. The reaction mechanism is also explored through capture of reaction intermediates. The analysis of the reaction mixture over different catalysts is presented and helps to understand the role of nickel and tungsten carbideduring the reaction.In the sixth chapter, we describe a new carburization reaction of biomass derived aldehydes to produce liquid fuels with8-14carbons. By constructing new C-C bonds, platform molecules condensed to fuel precursors through self-coupling over different metals. The fuel precursors with10-14carbons could be easily obtained though direct self-coupling of furfural,5-methyfurfural or aromatic aldehyde, the main components of lignocellulose, under mild conditions in water. After dehydration/hydrogenation, straight or branched alkanes with8-14carbons within diesel ranged fuels were obtained in moderate to high yield.In the last chapter, we present the summary and outlook.In conclusion, this thesis mainly focused on the conversion of biomass derived platform molecules into different chemicals and fuels through different catalytic systems, the performances of different catalysts with different activities and the influence on the products were studied and explored. Through the development of new catalytic systems, more applications of platform molecule will be present.更多还原