Strategies for the Separation of the Furanic Compounds HMF, DFF, FFCA, and FDCA from Ionic Liquids

Abstract

The catalytic upgrading of sugar derivatives into valuable building blocks represents an extremely important challenge intrinsic to the attempts to establish a green economy. However, the significance of separation and purification are often relegated to a marginal role or overlooked completely despite this aspect being critical for potential scale up. It is well established that the synthesis of 5-hydroxymethylfurfural (HMF) from sugars in ionic liquid media is a valuable, sustainable and high-yielding chemical pathway, but product separation has always remained an unresolved issue. In this contribution, the separation of HMF and three of its derivatives, 2,5diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) from ionic liquids is analyzed. Various ionic liquids are screened in order to obtain an optimal separation process. The extraction of HMF is studied from the hydrophobic methyltrioctylammonium ionic liquids with water, obtaining a favorable partition coefficient for the aqueous phase. In contrast, its derivatives, DFF, FFCA and FDCA, can be easily separated by phase separation. DFF retains its sublimation attributes in the ionic liquid and can be readily separated in quantitative yields in high purity. This behavior is observed in ionic liquids but is not achievable in common organic solvents. FDCA and FFCA are separated by water addition and precipitation. It is found that less water is required for the precipitation of these compounds compared to dimethylsulfoxide (DMSO), which is a frequently employed reaction medium for their generation. The energy balance for regeneration of the ionic liquid after water addition is estimated using the enterprise ionic liquids database ILUAM. This study provides a set of solvent design guidelines for the selective synthesis, isolation and purification of these compounds in ionic liquids, aiding future reaction design.

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

“…Crystallisation of the compounds was simulated through a separator unit in Aspen according to the literature conditions [54][55][56] needed to achieve full separation with the enthalpy of crystallisation for HMF and FDCA taken from the literature to be 19.8 kJ mol −1 (NIST 67 ) and 55.1 kJ mol −1 , 68 respectively. Utilities costs for steam, electricity, and waste water treatment (WWT) were estimated according the guidelines reported by Ulrich and Vasudevan 69 for petrochemical plants in the USA, which are based on the utility prices according to the Marshall and Swift (M&S) inflation index and the cost of energy.…”

“…38 The ultimate product, FDCA, can be separated from ionic liquids by water addition. When [bmim]Cl is used as the solvent, a composition of 40% is needed to achieve 5% solubility 55 and complete recovery can be achieved by cooling to 5°C. In the case of [bmim]Br, a smaller amount of water is needed for precipitation.…”

“…54 It has been found that HMF can be separated efficiently from hydrophobic, non-coordinating ionic liquids using water, while the partition coefficient is heavily compromised if hydrogen bonding acceptors are present. 55 However, these systems are affected by leaching of the ionic liquid into the water phase, which raises issues related to the toxicity and cost of these solvents. 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.…”

“…At room temperature, around 45% water composition (in DMSO) decreased the solubility of FDCA to less than 5%, while another study showed that, when using ionic liquids, the amount of water needed is even less (40% for [bmim]Cl and 20% for [bmim]Br; bmim = 1-butyl-3-methylimidazolium) to achieve the same low FDCA solubility. 54,55 Therefore, a two-step, one-pot reaction to synthesise FDCA from sugars is needed for these solvents in order to overcome the separation issues. Recently, Dumesic and co-workers established this concept in a GVL-water system in which fructose was dehydrated to HMF in 70% yield and then converted to FDCA in quantitative yield using a Pt/C catalyst.…”

Efficient Formation of 2,5-Diformylfuran in Ionic Liquids at High Substrate Loadings and Low Oxygen Pressure with Separation through Sublimation

“…[38][39][40] Moreover, our observation that the sublimation properties of DFF are retained in the ionic liquid and that the molecule can be easily separated under vacuum at relatively low temperature (80 °C) to provide a high purity product. 25 The selective oxidation of alcohols in ionic liquids has been studied widely and various systems based mostly on homogeneous catalysts have been proposed. 41,42 It is usually considered that aerobic oxidation is the most environmentally-friendly oxidation technique for these transformations since oxygen (at low pressures) is relatively cheap and safe.…”