Rapid, High‐Yield Fructose Dehydration to 5‐Hydroxymethylfurfural in Mixtures of Water and the Noncoordinating Ionic Liquid [bmim][OTf]

Abstract

The noncoordinating ionic liquid [bmim][OTf] (bmim=1‐butyl‐3‐methylimidazolium) is an effective and versatile solvent for the high‐yield dehydration of fructose to the platform chemical 5‐hydroxymethylfurfural (HMF) over short reaction times. In contrast to prior studies in which low yields were obtained for this transformation in ionic liquids (ILs) with noncoordinating anions, this contribution reveals that the water content is an essential parameter for an efficient reaction in ILs. Achieving the optimum amount of water can increase the yield dramatically by regulating the acidity of the catalyst and partially suppressing the side reaction caused by self‐condensation of HMF. Using acid catalysis in [bmim][OTf] with 3.5 % water content, yields above 80 % can be achieved at 100 °C in only 10 min, even at high (14 %) fructose loading. These results also suggest that [bmim][OTf] represents a superior medium for solvent extraction of HMF compared to halide‐based ILs, allowing the option of isolation or further valorization of the HMF formed.

Controlling the Reaction Networks for Efficient Conversion of Glucose into 5‐Hydroxymethylfurfural

“…Meanwhile, the noncoordinating [BMIM][OTf] IL is also an effective solvent for fructose‐to‐HMF dehydration, wherein the existence of small amount of water (e. g., 3.5 %) is crucial for achieving high HMF yields (ca. 80 %) after reaction at 100 °C for only 10 min . In most cases, no LA is detected, which is indicative of the inhibition of HMF rehydration and increase of HMF selectivity in these ILs‐mediated catalytic systems.…”

From sugars to FDCA: a techno-economic assessment using a design concept based on solvent selection and carbon dioxide emissions

“…Operating conditions with a water : MIBK ratio of 1 : 7 at 150°C were employed and these are typical of conditions reported previously to guarantee high selectivity. [18][19][20]60 It was calculated that 15% NaCl loading in the water phase will guarantee complete separation of HMF into the MIBK phase without the need for any further extraction unit. Complete selectivity will be assumed, even if improvements in process conditions are still needed.…”

“…Hexane has been widely used in the literature as an effective antisolvent for this purpose. 19 A distillation column operating at 1.2 bar is used to separate hexane from MIBK, followed by recycling of the hexane in the crystalliser, while the MIBK streams are collected and recycled to the feed.…”

“…The isolation of HMF has proved challenging due to the instability of this molecule and its high affinity with the reaction media, which make solvent extraction or distillation unfeasible. 18,19 Moreover, HMF undergoes decomposition even at room temperature, which makes storage on a large scale expensive due to the need for refrigeration. 20,21 However, there is still great interest in replacing PET with PEF due to its superior barrier proprieties (e.g., towards O 2 and CO 2 ) and the importance of exploiting renewable feedstocks in place of petrochemically-derived precursors to help reduce CO 2 emissions.…”

“…While separation is facilitated by the use of ionic liquids with non-coordinating anions, these media lead to substantially lower HMF yields compared to ionic liquids with coordinating anions. 19 Therefore, the efficiency of HMF synthesis in DMSO and ionic liquids cannot be usefully exploited due to separation issues. In contrast, FDCA has more favourable physical properties, which can aid the separation from these solvents.…”