Catalytic Dehydration Of Fructose To5-Hydroxymethylfurfural By Melamine-based Catalysts

5-Hydroxymethylfurfural (5-HMF), a versatile platform chemical perpared from biomass, is considered as a key intermediate which connects the biomass chemistry and petrochemical industry.5-HMF’s derivatives can be used to produce spices, pesticides, Pharmaceuticals, polyester, optoelectronic materials and other chemicals. Many studies have contributed to the developments and applications of new catalysts for5-HMF synthesis. In this paper, three kinds of acidic catalysts were prepared from melamine to catalyze the dehydration of fructose to5-HMF. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), Nitrogen adsorption-desorption, Thermo gravimetric analysis (TG), Scanning electron microscope (SEM), elemental analysis and acidity measurement. The influences of solvents, catalyst dosage, reaction temperature, reaction time, fructose concentration and the reusability of catalysts on the yield of5-HMF were investigated experimentally.Firstly, a pale yellow, transparent, sticky colloid catalyst SM was synthesized to catalyze the dehydration of fructose to5-HMF. The results showed that the catalyst SM was a homogeneous catalyst in fructose dehydration using dimethyl sulfoxide (DMSO) as solvent. Through the single-factor experiments, the optimum reaction conditions were found as:the catalyst SM dosage of20%, fructose concentration of0.05g/mL, reaction temperature of170℃and reaction time of20min. The maximum5-HMF yield of89.7%could be obtained in DMSO under the optimum reaction conditions.Secondly, a novel, reusable sulfonated melamine formaldehyde resin (SMFR) was synthesized and used in the preparation of5-HMF. It was found that a5-HMF yield of80.7%could be obtained in DMSO under the following optimum reaction conditions:the catalyst SMFR dosage of10%, fructose concentration of0.05g/mL, reaction temperature of160℃and reaction time of180min. The catalyst kept a high catalytic activity after it was used for five times, which indicates that the catalyst has a good reusability.Finally, a novel sulfonated carbonaceous material was prepared by using melamine formaldehyde resin as precursor to catalyze the dehydration of fructose to5-HMF. It was found that a5-HMF yield of79.8%could be obtained in DMSO under the following optimum reaction conditions:the catalyst SMC dosage of5%, fructose concentration of0.025g/mL, reaction temperature of180℃and reaction time of30min. The catalyst kept a high catalytic activity after it was used for five times, which indicates that the catalyst has a good reusability.