Extraction And Synthesis Of 5-HMF In Organic Solvent/Ionic Liquid Boiling Biphasic System

5-Hydroxymethylfurfural(5-HMF),which has been widely recognized as a biomass-derived intermediate for the production of various non-petroleum based chemicals and fuels,can be produced from glucose and cellulose in ionic liquid solvents.However,the reactions and the separation of product from an ionic liquid through extraction usually results in low mass transfer rate because of the high viscosity of an ionic liquid and the large density difference between an ionic liquid and organics even under strong stirring.This work was performed specifically to identify the primary considerations in establishing a bubbling-promoted biphasic system and ultimately improve mass transfer during extraction or reaction.A new component as bubbling reagent was added in an organic solvent/ionic liquid biphasic phase and was mediated at constant “boiling-liquefying” state,through which the turbulence and mass transfer of the biphic system were enhanced.On the basis of our fundamental understanding of the dominant property of bubbling during extraction,we identified the primary factors in generating bubbling effect.Furthermore,bubbling was employed to synthesize 5-HMF from glucose or cellulose in a MIBK/[BMIM]Cl/CrCl3 system by using appropriate bubbling reagents.The mechanism by which bubbling effect enhances mass transfer during extraction and reaction was extensively discussed.During extraction in the MIBK/[BMIM]Cl model biphasic system,bubbling reagents,such as methanol and acetonitrile,constantly gasify from and dissolve into the [BMIM]Cl phase;these bubbling reagents thus exhibit dynamic equilibrium between the two phases.The bubbles float across the ionic phase and break through the interface between the two phases.Bubbling dynamically enhances the turbulence of the mixture and increases the interface area;both of these phenomena are beneficial for the rapid transfer of 5-HMF from the ionic liquid phase to the extraction phase,improving extraction rate.During reaction of glucose or cellulose into 5-HMF in the organic solvent/[BMIM]Cl/CrCl3 biphasic system,the bubbling reagents partitioned in the [BMIM]Cl phase are constantly gasified from and dissolved into the[BMIM]Cl phase.This process dynamically enhances the turbulence of the reactionphase,facilitates the transfer of 5-HMF from the reaction phase to the extraction phase and reduces the occurrence of localized side reactions.The necessary characteristics of a suitable bubbling reagent are that: its initial bubbling temperature should be lower than the reaction temperature so that bubbles form at the reaction temperature;it should be mainly distributed in the [BMIM]Cl phase so that the system can generate sufficient bubbles.The key operating procedures in establishing bubbling biphasic systems include creating a temperature gradient from top to bottom of the biphasic system and superheating the bubbling reagent in the [BMIM]Cl phase.