Preparation Of5-hydroxymethylfurfural From Carbohydrates Catalyzed By Functionalized Ionic Liquids

With the rapid development of the world economy, energy demand was increasing, and itwas projected that fossil fuels cannot be considered as the world’s main source of energy formore than100years. As a result, carbohydrates have been the target of intensive research forconversion and utilization as chemicals. It had the potential to become a promising alternativeto fossil resources for the sustainable production of5-hydroxymenthylfurfural (HMF), aversatile and key intermediate in the bio-fuel chemistry and petrochemical industry and isconsidered to be one of the top12bio-based building blocks listed by the U.S. Department ofEnergy.In this thesis, we have mainly studied on the degradation of carbohydrates (includingmonosaccharides, disaccharides and polysaccharides) into HMF in the presence of variousionic liquids (ILs), metal salts and inorganic-organic solvents. The relative research contentsare shown as follows:(1) First, herein we reported a novel catalytic system that consisted of1-allyl-3-methy-limidazolium chloride ([AMIM]Cl) and N,N-Dimethylformamide (DMF) without anyadditional metal salts or acids, which led to reasonable HMF yields (84.9%) and selectivities.In addition, the degradation mechanism of fructose catalyzed by [AMIM]Cl was alsoproposed in the thesis, theoretical calculation results showed that [AMIM]Cl expressed amore efficient catalytic activity than [BMIM]Cl. At last, the recycling of catalysis system wasput forward in our study for fructose degradation and the catalysis system maintained goodperformances even after five runs.(2) Next, we initially attempted to build several different catalytic systems by using1-alkyl-3-methylimidazolium chloride or bromide as a solvent class. Various acidic ILs,including1-methylimidazolium hydrogen sulfate ([MIM][HSO4]), N-methyl-2-pyrrolidoniumhydrogen sulfate ([NMP][HSO4]),1-(4-sulfonic acid)-propyl-3-methylimidazolium hydrogensulfate ([C3SO3HMIM][HSO4]) were synthesized and employed as catalysts for the reaction.Our method was distinguished from previous reports in that we have observed high yields ofHMF from sucrose and fructose without adding any metal salts. In addition, the combinationof [AMIM]Cl, acidic ILs and metal chloride (CoCl2) performed well in conversion of othersugars. The research aimed to make a mechanistic insights on the direct transformation ofsugars to HMF, including glucose, fructose, galactose, sucrose, maltose and lactose. With thecatalyst of [NMP][HSO4], a HMF yield of87%was achieved from sucrose. Our studyshowed that some, but not all mono-and disaccharides, can be transformed effciently into HMF. We believe these efforts will provide a molecular level understanding of the reactionprocess for the IL-promoted conversion of fructose to HMF, and help us to design anddevelop a new catalytic system for conversion of sugars to HMF.(3) Finally, the direct transformation of cellulose and carbohydrates into HMF in thesolvent of [BMIM]Cl by using dual-core sulfonic acidic ionic liquids as the catalysts andmetal salts as co-catalysts was investigated, aiming at a more environmental feasible processnot involving chromium. From high throughput screening of various metal salts, acombination of1,2-bis (N-propane sulfonic acid imidazolinium) ethane methanesulfonate([bi-C3SO3HMIM][CH3SO3]) and manganese chloride (MnCl2) was found as the mosteffictive catalyst. HMF was directly afforded from cellulose in66.5%yield. In the principlesof green engineering, the recycling of catalyst was put forward in our system for cellulosehydrolysis and these catalysts maintained good performances even after four runs.Furthermore, various sugars and lignocellulosic raw materials could be directly converted intoHMF in reasonable yields under these conditions. The mechanism that explains the highactivity of ILs combination with MnCl2was also proposed.In conclusion, ionic liquid catalysts and solvents were found to be effective compoundsto promote the conversion of monosaccharides, disaccharides and polysaccharides, whichprovide some new methods and choices to transform carbohydrates to several platformchemicals.