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

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.