Green chemical conversion of fructose into 5-hydroxymethylfurfural (HMF) using unsymmetrical dicationic ionic liquids under mild reaction condition

• Unsymmetrical dicationic imidazolium based ILs were synthesized.
• Imidazolium, pyridinium, and triethyl ammonium cations were used.
• Prepared ILs showed efficient catalytic activity in fructose dehydration.
• 100% fructose conversion and 92.3% HMF yield was obtained.
• 70 °C temperature and 40 min reaction time gave the good results.

A series of unsymmetrical dicationic ionic liquids (ILs), in which each IL is associated with two unsymmetrical nitrogen containing rings with their individual anions were synthesized and utilized it as catalyst in dehydration of fructose. For the synthesis of unsymmetrical dicationic ILs we utilized imidazolium, pyridinium, and triethyl ammonium as cationic moiety and HSO4-,CH3SO3-, and Br− as an anionic moiety. The newly synthesized all unsymmetrical ILs were showed efficient catalytic activity in dehydration of fructose into 5-hydroxymethylfurfural (HMF) in mild reaction condition. Especially ([tetraEG(mim) (triethylamo)] [HSO4-]2) unsymmetrical IL was showed higher catalytic activity among all synthesized ILs, it exhibited 100% consumption of fructose and achieved 92.3% HMF yield in 40 min reaction time using 10 wt% of catalyst at 70 °C reaction temperature. The present environmentally benign catalytic system is found to be very convenient, high yielding, fast, and clean method for selective dehydration of fructose into HMF in absence of solvent and co-catalyst.

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