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

Abstract

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) using oxygen (1 atm) with a TEMPO and CuCl catalyst system is investigated using a range of imidazolium-based ionic liquids (ILs) and various bases at different HMF substrate loadings (10-50%). This represents the first example of HMF to DFF conversion in ionic liquid media under homogeneous catalysis conditions, revealing dramatic differences in performance between the ILs. In the non-coordinating, hydrophobic ionic liquid, [bmim][NTf2], 90% DFF yield is obtained at 5 mol% catalyst loading after 6 hours at 80 °C at a very high 40% HMF loading. Increasing the temperature to 100 °C leads to a lower yield, attributed to loss of volatile TEMPO from the reaction medium. A system using TEMPO and pyridine immobilized within the ionic liquid [bmim][NTf2] results in selective conversion of HMF to high purity DFF. It also allows the DFF formed to be isolated by sublimation in 81% yield before a further cycle is performed. Subsequent catalyst deactivation is probed by X-ray photoelectron spectroscopy (XPS). Synthesis from fructose in a two-step process achieves a 55% isolated DFF yield. This approach overcomes significant drawbacks previously reported for this transformation, such as solvent toxicity, separation and purification problems as well as the need for high oxygen pressures. Further oxidation of HMF with this system leads to a 62% yield of 5-formyl-2furancarboxylic acid (FFCA). The separation of this compound can be achieved by sublimation of DFF followed by solvent extraction.

Sugar dehydration to 5-hydroxymethylfurfural in mixtures of water/[Bmim]Cl catalyzed by iron sulfate

“…49 With regard to the HMF separation in ionic liquid, Hallett and co-workers recently proposed some different strategies, such as i) using a non-coordinating ionic liquid (e.g., [Bmim]OTf) as solvent, 50 ii) using hydrophobic methyltrioctylammonium ionic liquids with less water as media 51 and iii) in situ conversion of the formed HMF into useful furan chemicals like 2,5-diformylfuran (DFF). 52 Additionally, Wei et al 53 studied the vacuum reactive distillation to separate HMF in ionic liquids, and obtained high isolated yield in short time but high requirements for vacuum conditions. Shi et al 25 used supercritical CO2 to induce a phase separation of miscible ionic liquid with acetone and thus increasing the partition coefficient, while the harsh conditions were needed.…”

One‐Step Reductive Amination of 5‐Hydroxymethylfurfural into 2,5‐Bis(aminomethyl)furan over Raney Ni

“…5-Hydroxymethylfurfural (HMF) is one of the most promising biomass-derived platform compounds during the past two decades, [1][2][3][4][5][6] from which a series of chemicals such as 2,5dimethylfuran (DMF), [7][8][9][10] 2,5-dihydroxymethylfuran (DHMF), [11][12][13][14] 2,5-diformylfuran (DFF), [15][16][17] 2,5-furandicarboxylic acid (FDCA) [18,19] and other ring-opened compounds [20,21] have been synthesized with satisfactory yields on laboratory scales. As reported, furan ring outperforms benzene ring and cyclohexane ring in many aspects while being used as a building block for polymers because of its improved barrier properties for oxygen, carbon dioxide, and water vapor as well as better thermal stability and mechanical properties.…”

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

“…For the conversion of HMF to FDCA, at least 20% water content was specified as this is needed in the oxidation reaction to favour the formation of the geminal diols needed for the aldehyde oxidation step. 64 For the dehydration reaction, the highest yield and substrate loadings reported in the literature were used for the different processes. For the purposes of the study, complete selectivity for FDCA was assumed in the oxidation step but this is clearly an area in which improvement is needed; this aspect was therefore further evaluated by comparing the results reported in the literature.…”