The Research Of 5-hydroxymethylfurfural Preperation From Fructose Catalyzed By Modified MIL-101 Porous Materials

5-hydroxymethylfurfural(5-HMF)is a highly representative biomass based platform compound,which can be used to prepare compounds with higher added value.The traditional way of preparing 5-HMF is using sulfuric acid as catalyst.It is easy to corrode equipment and pollute the environment in the process of production.Although the solid acid catalysts have solved these problems,their catalytic sites are only on the surface and have low activity.The aim of this research is to synthesize a green and efficient Metal-organic frameworks material(MOFs)for the preparation of 5-HMF,which is environmentally friendly while further improving the yield.First of all,synthesized MIL-101(Cr)porous material as the initial carrier for catalyst,and optimized the synthesis time,raw material and subsequent treatment.It was found that the optimum conditions are as follows:the synthetic reaction was 8 hours,a proper amount of HF was added and activated by ethanol.The MIL-101(Cr)porous material was modified by bromine and further prepared MIL-101(Cr)-PMAi-Br catalyst.The products were characterized by FT-IR,XRD,TEM,BET,EDS and XPS.The results showed that carbonyl group(C=O)and aminocarbonyl group(CO-NH)were successfully loaded on MIL-101(Cr)carrier,indicating that MIL-101(Cr)-PMAi-Br catalyst was successfully synthesized;The crystal structure is a positive eight plane before and after modification;The specific surface area is up to 2372 m2/g,indicating that the catalyst has good pore structure;The bromination rate of MIL-101(Cr)-PMAi-Br catalyst is 65%,and the element distribution is uniform.Secondly,MIL-101(Cr)-PMAi-Br was used to catalyze the dehydration of fructose to prepare 5-HMF under atmospheric pressure.The effects of reaction temperature,reaction time,amount of catalyst and solvent ratio on 5-HMF yield and fructose conversion rate were investigated.The results show that the yield of 5-HMF increases with the increase of the reaction temperature,but if the temperature is too high,the yield will decrease by the side reaction and solvent decomposition;with the increases of reaction time,the yield increases first and then tends to be stable;the amount of catalyst increases,the yield increases first and then decreases;and only a small amount of water can promote the reaction in the solvent.The optimum conditions are as follows:reaction temperature 100?,reaction time 2.5h,fructose concentration 0.55M,catalyst MIL-101(Cr)-PMAi-Br dosage 20mg/ml,solvent DMSO:water=9:1,5-HMF yield up to 92.74%.In addition,After 5 cycles of MIL-101(Cr)-PMAi-Br catalyst,the yield of the product only decreased by 14%.Finally,the MIL-101(Cr)-PMAi-Br catalyst was magnetized and used for the preparation of 5-HMF.The catalyst were characterized by FT-IR,XRD,SEM,BET and saturation magnetization.The results show that the absorption peak and diffraction peak of Fe304 exist in the catalyst after magnetization,which proves that the magnetic has been loaded successfully;The size of magnetic MIL-101(Cr)-PMAi-Br catalyst has no obvious difference from before,indicating that the crystal structure has not been destroyed;It has typical paramagnetic properties.The effects of magnetic properties on the yield of 5-HMF and the recycling performance of catalysts were investigated.The results show that the 5-HMF yield is 78.29%,which decreases slightly after the use of magnetic MIL-101(Cr)-PMAi-Br catalyst,but the greater advantage is tofacilitate the separation of the catalyst from the product,reduce the energy consumption and simplify the process.