Conversion Of Carbohydrates Into 5-hydroxymethylfurfural Catalyzed By Functionalized Ionic Liquids

With the growing of global energy crisis and rapid depletion of conventional fossil sources, new energy development and utilization has become the main work for countries around the world. Carbohydrates are a reproducible and abundant biomass resources, and have gradually became the focus of study. A series of biofuels and high value-added fine chemicals products were prepared from carbohydrates. Particularly, 5-hydroxymethylfurfural, a platform in biomass and petrochemical industry, are the focus and the subject of the research in the future. Besides, 5-hydroxymetnylfurfural has important application value and was recommended as one of 12 bio-based building blocks by the U.S Department of Energy.The catalyst of ionic liquids, alkaline earth metal chlorides and ionic liquids were used to dehydration of carbohydrates into HMF in the paper. The main content in the work are as follows:First, a variety of polyethylene glycol-400-functionalized dicationic acidic ionic liquids(PEG400-DAILs) were synthesized and tested in the dehydration of fructose. Among these catalysts, hydrogen sulfate anion-based ILs showed the higher catalytic performance in the conversion of fructose. The highest HMF yield of 96.5 % was obtained after 60 min at 110℃ in DMSO. The effects of catalyst concentration, reaction time, reaction temperature, and solvents were systematically investigated. In addition, the generality of the catalysts was examed by processing inulin and sucrose to HMF with yield of 71.9 % and 52.1 % under certain conditions, respectively. The used IL catalyst could be separated and recycled repeatedly without significant loss of catalytic activity even after six runs.Next, the SO3H-functionalized polymeric ionic liquids were prepared and studied its effect in catalyzing fructose dehydration into HMF. Hydrogen sulfate anion and PW12O40 anionic based ILs catalysts showed perfect catalytic performance in the conversion of fructose. The highest HMF yield were 91.0% and 86.2%, respectively, after 60 min at 110 ℃ in DMSO. On that basis, the effects of different anions on HMF yield were researched. In addition, the catalytic effects of the catalysts were studied by converting inulin and sucrose into HMF with yield of 43.1% and 38.8%, respectively. After the reaction, hydrogen sulfate anion-based ILs could be separated from the product mixture by centrifugation and recycled repeatedly with good catalytic performance even after five runs.Finally, the synergetic effect of BF4 anion ionic liquid and alkaline earth metal chlorides(mainly including Mg Cl2·6H2O and Ca Cl2·2H2O) in the conversion of glucose to HMF was researched in DMA. Compared with simple Mg Cl2·6H2O, the system of [BMIM]BF4-Mg Cl2·6H2O can effectively improve the HMF yield from glucose, and the maximum value was 41.7%. What’s more, the influence of BF4 anion ionic liquids with different substituents([VMIM]BF4 and [MAMIM]BF4), and 1-butyl-3-methyl imidazolium ionic liquids with different anions([BMIM]Cl and [BMIM]Br) on conversion of glucose into HMF was discussed carefully in the paper. In addition, the dehydration mechanism of glucose into HMF using Mg Cl2·6H2O as catalyst have been proposed. HMF preparation from galactose, cellobiose and sucrose over alkaline earth metal chlorides promoted with BF4 anion ionic liquids were also systematically studied, the results showed that BF4 anion ionic liquids acting as a cocatalyst can effectively improve the yield of HMF as a cocatalyst.