Synthesis Of 5-Hydroxymethylfurfural Via Dehydration Of Fructose

5-Hydroxymethylfurfural is a new type of platform compound. There was a hydroxymethyl and an aldehyde existed in the molecular, it can be transformed into hundreds of high value-added products via hydrogenation, esterification, halogenation and hydrolyzation reactions. Therefore 5-hydroxymethylfurfural received extensive attention of researchers all around of the world.Four kinds of Brφnsted acidic ionic liquids were synthesized: [HO₃S-(CH₂)₃-mim]Cl,[HO₃S-(CH₂)₃-mim]H₂PO4,[HO₃S-(CH₂)₃-mim]HSO₄,[HO₃S-(CH₂)₃-mim]pTSA; Brφnsted-Lewis dual-acidic ionic liquids: [HO₃S-(CH₂)₃-mim]Cl-ZnCl_<sub>2, [HO₃S-(CH₂)₃-mim]Cl-FeCl_<sub>3 and [HO₃S-(CH₂)₃-mim]Cl-CrCl_<sub>3. The structure and acidity of acidic ionic liquids were characterized, the results showed that the target compounds were synthesized. Using tosylate as the catalyst, the yield of 5-hydroxymethylfurfual was 86.7 % under the optimum reaction conditions as follows: fructose ₂ g, tosylate 1.8 mmol, n-butanol 15 ml, reaction time 5 min and reaction temperature 150℃. The results showed that n-butanol had the stable performance to 5-hydroxymethylfurfual and it had the benefit to the product purification and recycled use of solvent because of the low boiling point.When Brφnsted acidic ionic liquids were used as the catalyst, [HO₃S-(CH₂)₃-mim]Cl showed a better catalytic effect. The optimum reaction conditions as follows: fructose ₂ g, catalyst [HO₃S-(CH₂)₃-mim]Cl 1.₂ mmol, n-butanol 15 ml, reaction time 15 min, reaction temperature 180℃, the yield of product was 90.1 %; while the recycled performance of the catalyst was investigated, the yield of product was 89.₂ % after reused five times. The results showed that Brφnsted ionic liquids had good reused performance.Using Brφnsted-Lewis dual-acidic ionic liquids as the catalyst, [HO₃S-(CH₂)₃-mim]Cl-CrCl₃ had a better catalytic effect. The yield of 5-hydroxymethylfurfual was 9₃.4 % under the optimum reaction conditions as follows: fructose ₂ g, [HO₃S-(CH₂)₃-mim]Cl-CrCl₃ (n([HO₃S-(CH₂)₃-mim]Cl) : n(CrCl₃)=1:1)1.₂ mmol, n-butanol 15 ml, reaction temperature 180℃and reaction time 15 min. When the ionic liquids were reused five times, the yield of product was near 9₂.6 %. The results showed that the catalyst had good reused performance.In the dehydration of fructose to 5-hydroxymethylfurfural, acidic functional ionic liquids was not only overcame the flaws of conventional acids can not be avoided, but also finished the work of reaction-separation integration and the recycle of catalyst. Can be seen, the work expanded the application fields of the ionic liquids and provided the important basis to the application in the preparation of 5-hydroxymethylfurfural via biomass sugar.