Highly Efficient Conversion Of Fructose Into 5-hydroxymethylfurfural In Ionic Liquid At Room Temperature

5-Hydroxymethylfurfural(HMF)is an important platform compound derived from biomass.With HMF as a raw material,a lot of value-added chemicals can be obtained.The early work on the HMF preparation mainly focused on fructose dehydration in water or organic solvents.Organic solvents usually pose environmental concerns and the separation of HMF from solvent may be expensive,which limits the use of organic solvents in HMF preparation.Ionic liquids can be regarded as green solvents due to their low vapor pressure,good thermal stability and large liquidus temperature range.In the past decade,conversion of fructose into HMF in ionic liquids has aroused academic interest.The reported work on HMF preparation is usually done at high temperature to enhance the HMF yield,but high temperature also results in byproducts and more energy consumption.Thus,it is of great significance to develop media that are suitable for HMF preparation at room temperature.To this end,the following study has been made:1.Efficient conversion of fructose into 5-hydroxymethylfurfural in pyrrolidinium based ionic liquid at room temperatureIn view of environment protection,it is of great significance to use green ionic liquids to replace the organic solvents as the media for fructose dehydration to HMF.The sugar-dissolving ionic liquids solid.To realize the room-temperature conversion of fructose to 5-hydroxymethylfurfural,some organic solvents or some other ionic liquids have to be added to make the medium in a liquid state.There are few reports on the conversion of fructose into HMF in neat ionic liquid at room temperature are few.Pyrrolidinium based protic ionic liquids,which are liquidus at room temperature and also capable of dissolving sugars,are found to be a suitable medium.In this work,several pyrrolidinium based protic ionic liquids were synthesized and used as mediua for fructose dehydration.Among the tested ionic liquid,[Pyrr]Cl(pyrrolidinium chloride)is better.The HMF yield at 40 ? after 6 h is 83.25%.2.The physicochemical properties of binary ionic liquid mixture of[HNMP][CH3SO3]/[Bmim]Cl and its application for room-temperature fructose dehydration into 5-hydroxymethylfurfuralVia heating first and then cooling,binary ionic liquid(IL)mixture of N-methyl-2-pyrrolidonium methyl sulfonate([HNMP][CH3SO3])and 1-butyl-3-methylimidazolium chloride([Bmim]Cl)could form a liquid at room temperature.DSC curves show that thermal behavior of the binary IL mixture could be changed by the variation of the composition and the glass-transition temperature could be as low as-63?.The physicochemical properties of the binary IL mixtures have been characterized.It is found that,with the increase of the content of[Bmim]Cl,the hydrogen-bond accepting ability(?)of the binary IL mixture rises whereas the hydrogen-bond donating ability(a)deceases.With this binary IL mixture as medium,fructose could be converted into 5-hydroxymethylfurfural(HMF)effectively at room temperature.The HMF yields at a given time in IL mixtures of different mole fractions are closely correlated with the physicochemical properties,especially the ? and ? values,which have notable influences on formation rate of HMF.Unlike our previously reported media formulated by ILs and alcohols,the present binary IL mixtures could avoid the negative alcohol effect on the fructose dehydration into HMF at room temperature.