Microwave Heated Honversion Of Fructose Into 5-HMF Over Sulfonated Solid Acid

We now face a problem of increasingly shortfall of oil resources used to manufacture chemical feedstock and energy needed by society.The substitutive resource is one of the most important fields of research and utilization at the moment.Recently,as an abundant,geographically ubiquitous,renewable,low sulfur content and inexpensive resource,biomass is a promising succedaneum to fossil energy in the production of various materials,chemicals,fuels and chemical intermediates.In the transformation of biomass,how to transform sugar into 5-hydroxymethylfurfural（5-HMF）had attracted extensive attention.In this work,a sequence of sulfonated carbon solid acid catalysts were prepared by template method using fructose as the carbon source and zinc chloride as the catalyst and template.In addition,a new type of zirconia-based solid acid was prepared by co precipitation method(SO₄^2-/NbO_x-WO_x-ZrO₂,SO₄^2-/WO_x-ZrO₂).These synthesized catalysts were analyzed by XRD,FTIR,SEM,BET and NH₃-TPD,and the total amount of surface acid sites of these carbon-based solid acid catalysts were analyzed by chemical adsorption-desorption of ammonia combine with standard curve of ammonia.The reaction of fructose dehydration to 5-hydroxymethylfurfural（HMF）was examined using these catalysts at assistance of microwave in dimethyl sulfoxide（DMSO）.The influence of microwave power,different catalysts,amount of catalyst,fructose content,reaction temperatures,reusability of the catalyst were investigated.The carbon-based catalyst prepared by the template method has a very high activity.The results showed that C₂-SO₃H sample had the best activity.A 5-HMF yield of 86.8%and fructose conversion of 98.9%were achieved at 170℃in DMSO after 3 min.The zirconia-based catalysts also showed good activity.The experimental results show that the activity of the catalystSO₄^2-/NbO_x-WO_x-ZrO₂ is lower than that of the SO₄^2-/WO_x-ZrO₂ catalyst when the zirconium-based catalyst is used for the dehydration of fructose.A 5-HMF yield of 82.4%and fructose conversion of 96.4%were achieved at160℃in DMSO after 3 min.Moreover,this synthetic strategy of microwave assistance comparing with traditional method has advantages of accelerating reaction rate and simplifying work-up procedure.