Highly Efficient Room-temperature Conversion Of Fructose Into 5-hydroxymethylfurfural Promoted By Binary Ionic Liquids In Alcohol

5-Hydroxymethylfurfural (HMF) is a new platform chemical, from which hundreds of high value-added chemicals can be derived. However, the reported HMF preparation is generally carried out under high temperature. The high energy consumption limits its large scale production. Aiming at the limitation, the author of the present thesis carried out the following research works:1. Room-temperature ionic liquid system converting fructose into HMF in high efficiency.The dehydration of fructose into HMF promoted by ionic liquids [Bmim]Cl and [HNMP][CH3SO3] in ethanol solvent was investigated. Two intermediates captured in time-dependent HPLC determinations are identified and structurally characterized by in situ 1H NMR and online ESI(+)-MS/MS. Studies on the influence of the ionic liquids (ILs) on the formation and transformation of the intermediates indicate that [HNMP][CH3SO3] promotes the formation of the intermediates, while [Bmim]Cl promotes their transformation. The contribution of the component ions of the ILs to the dehydration originates from their activation toward the leaving of OH on fructose or the intermediates via the formation of multiple hydrogen bonds. This kind of weak interaction appears only at low temperature. On the basis of the present study and the related literature, we propose a concerted mechanism for the binary IL-promoted conversion of fructose into HMF at room temperature.2. The alcohol effect and the related mechanism on the fructose dehydration into HMF in the deep eutectic solvent of [Emim]Cl/alcohol.The ionic liquid [HNMP]Cl-catalyzed dehydration of fructose into HMF in deep eutectic solvents (formed by [Emim]Cl and different alcohols) were investigated. The results showed that isopropanol was the optimum alcohol for the conversion system. Studies on the mechanism of the alcohol effect indicated that an alcohol could influence the formation of intermediates and their further transformation via the hydrogen bonds formed with [Emim]Cl and [HNMP]Cl. For the normal alcohols, the shorter the chain, the higher the polarity, and the stronger the ability to form the hydrogen bond; as a result, the alcohol with the shortest chain has the greatest negative effect on the fructose dehydration. For the branched chain alcohols, the existence of steric hindrance led to their weaker ability to form the hydrogen bond with the ionic liquid, so that their negative effects on the conversion were much smaller. The DES composed of equal moles of [Emim]Cl and isopropanol is the best one for the conversion of fructose into HMF catalyzed by [HNMP]Cl with an HMF yield of up to 89% after 3 h reaction at 25℃.