Green Organic Synthesis Of Biomass-derived Platform Compounds

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.