Ionic liquid with metal complexes: An efficient catalyst for selective dehydration of fructose to 5-hydroxymethylfurfural

• 95.5% Yield of HMF was obtained in mild condition by the dehydration of fructose.
• Ionic liquid containing transition metal complexes used as catalysts.
• Transition metal complexes have a remarkable effect on the dehydration of fructose.
• First example of IL with metal complexes in fructose dehydration.

The dehydration of D-fructose has been studied with different kinds of pyridinium based dicationic ionic liquids as catalyst. The results showed that 1,1′-hexane-1,6-diylbis (3-methylpyridinium) tetrachloronickelate (II) [C6(Mpy)2][NiCl4]2− in DMSO and 1,1′-decane-1,10-diylbis (3-ethylpyridinium) dibromide [C10(Epy)2]2Br− without DMSO have high catalytic activity. Highly efficient and selective dehydration of D-fructose to 5-hydroxymethylfurfural (HMF) was achieved in dimethyl sulfoxide (DMSO) under mild conditions with a fructose conversion of 95.6% and 95.5% HMF yield was achieved in 60 min reaction time at 110 °C and 87.1% yield obtained from [C10(Epy)2]2Br− without DMSO at 100 °C in 90 min reaction time. The ionic liquids used in this study will benefit many biofuel-related applications.

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