Conversion Of Carbohydrates Into 5-Hydroxymethylfurfural Catalyzed By Solid Acid In Deep Eutectic Solvents

The preparation of 5-hydroxymethylfurfural?5-HMF?from carbohydrates has been paid a great attention at present.As an important platform chemical,5-HMF has broad application in fuel,pharmaceutical,fine chemical,polymer material and other industries.Currently the relevant research mainly focused on reactions with imidazolium-based ionic liquids as solvents and metal chlorides as catalysts.However,the conventional ionic liquids are usually very expensive and the metal chlorides are toxic and not environmentally friendly.In this work,the preparation of 5-HMF from carbohydrates dehydration by using cheaper and environmentally friendlier deep eutectic solvents?DES?and using solid acids as calalysts has been investigated.An extraction-reaction synergistic method was proposed to improve the yield of 5-HMF.A solid acid catalyst SO₄^2-/ZrO₂-Al₂O₃ was prepared by co-precipitation and impregnation method,the structure and properties of this solid acid was investigated by using Hammett indicator,FT-IR,XRD,BET,SEM analysis methods.The results indicated that the SO₄^2-was introduced into catalyst and it was absorbed on the surface of supports by means of chelating ligand.The introduction of aluminum oxide delayed the crystal transformation of zirconium and resulted a more stable tetragonal phase.The solid acid gives not only a good stability but also a superacid property.The properties of the solid acid depends on the calcinations temperature and are optimized at a temperature of 500?.SO₄^2-/ZrO₂-Al₂O₃ as catalyst,the conversion of fructose into 5-HMF in different DESs has been investigated.The results show that ChoCl/Oxalic acid is a relatively good solvent for the reaction.Ethyl acetate is the best extractant.At optimized reaction conditions: V?DES?/V?AcOEt?is 2:3,Zr-Al mole ration is 1:1,reaction time 20min at 80?,0.1g fructose,a yield of 5-HMF as high as 91.3% was obtained and the addition of ethyl acetate as the extractant in the reaction system was proved to be effective.The preparation of 5-HMF from glucose using SO₄^2-/ZrO₂-Al₂O₃ as catalyst and in different DESs was studied.The results show that choline chloride/oxalic acid DES as the solvent and at optimized reaction conditions: Zr-Al mole ration is 1:3,reaction time 20min at 140?,the 5-HMF yield is 37.2%.The humans is mainly composed of 5-HMF.The dynamics of the conversion of fructose into 5-HMF was studied.The apparent activation energy of decomposition of fructose in DES was 19.23 kJ/mol,which is much lower that that of decomposition of fructose in high temperature liquid water?42.44 kJ/mol?.