Dehydration of Carbohydrates to 5-Hydroxymethylfurfural in Ionic Liquids Catalyzed by Hexachlorotriphosphazene

Highly efficient synthesis of 5-hydroxymethylfurfural (HMF) by dehydration of carbohydrates was catalyzed by hexachlorotriphosphazene (N₃P₃Cl₆) in ionic liquids.

Development of efficient catalysts for the dehydration of carbohydrates to produce 5-hydroxymethylfurfural (HMF) is a very attractive topic. In this work, dehydration of fructose catalyzed by three organic molecules, including hexachlorotriphosphazene (N₃P₃Cl₆), trichloromelamine (C₃N₆H₃Cl₃) and N-bromosuccinimide (NBS), was studied in ionic liquids. It was discovered that the three organic molecules had high activity in accelerating the dehydration of fructose and N₃P₃Cl₆ was the most efficient catalyst among them. The effects of amount of catalysts, temperature, solvents, reaction time, and substrate/solvent weight ratio on the reaction were investigated using N₃P₃Cl₆ as the catalyst and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as the solvent. It was demonstrated that the N₃P₃Cl₆/[Bmim]Cl catalytic system was very effective for catalyzing the reaction. The yield of HMF could reach 92.8% in 20 min at the optimized conditions and the N₃P₃Cl₆/[Bmim]Cl system could be reused. Further study indicated that the N₃P₃Cl₆/[Bmim]Cl system was also effective for the dehydration of sucrose and inulin and satisfactory yield could be obtained at suitable conditions.