Preparation Of 5-hydroxymethylfurfural By Efficient Conversion Of Glucose In Deep Eutectic Solvent

The rapid development of society is accompanied by the predatory exploitation and utilization of non-renewable resources such as petroleum,which causes serious damage and pollution to the ecological environment.The development of renewable lignocellulosic biomass resources to prepare biomass-based platform compounds,which can partially replace petroleum-based chemicals,has become one of the effective ways to deal with the energy crisis and alleviate the contradiction between resources,environment and economic and social development.The development of renewable lignocellulosic biomass resources has become the focus of researchers in the field of energy and chemical industry worldwide.5-hydroxymethylfurfural（5-HMF）is a multipurpose bio-platform chemical that serves as a bridge linking biomass with Petrochemical refining.Catalyst and solvent play a key role in the production of 5-HMF from lignocellulose.In view of the problems existing in the existing 5-HMF production process.1)in the water reaction system,5-HMF is easy to be further hydrated to produce levulinic acid and formic acid,resulting in low yield of 5-HMF;2)Metal salt catalysts are difficult to recycle and face the problem of sewage discharge;3)Heterogeneous catalysts are unevenly dispersed in high viscosity solvents,and the pore structure of heterogeneous catalysts is blocked by the by-product humin.In this thesis,Deep eutectic solvent（DES）with both solvent and catalytic function is designed and developed.Glucose is dehydrated to produce 5-HMF without additional metal salt catalyst and heterogeneous catalyst.The specific research contents are as follows:1)The effects of hydrogen bond acceptor,hydrogen bond donor and hydrogen bond acceptor/hydrogen bond donor molar ratio on the production of 5-HMF from glucose catalyzed by DES were systematically investigated.The experimental results showed that TEBAC/FA（1:2）DES prepared with triethylbenzyl ammonium chloride（TEBAC）as hydrogen bond acceptor,formic acid（FA）as hydrogen bond donor and hydrogen bond acceptor/hydrogen bond donor molar ratio of 1:2 showed excellent catalytic performance and solvent effect in the preparation of 5-HMF from glucose dehydration.2)The effects of reaction conditions such as reaction time,reaction temperature,initial glucose concentration and water content of DES on the production of 5-HMF from glucose catalyzed by TEBAC/FA（1:2）DES were systematically investigated.The experimental results showed that under the optimum reaction conditions of reaction temperature 150℃,reaction time 60 min and mass ratio of glucose to DES 1:40,the conversion of glucose was100% and the yield of 5-HMF was 30.5±1.0%.It should be noted that under the optimum reaction conditions,when the water content in TEBAC/FA（1:2）DES increased to 10wt%,the yield of 5-HMF increased to 30.9±1.4%.When the water content in DES increased to70wt%,the yield of 5-HMF was 36.5±1.0%,and the yield of levulinic acid was 8.0±1.4%.3)TEBAC/FA（1:2）DES was extended to catalyze the production of 5-HMF from fructose and cellobiose.When the reaction temperature was 150℃ and the mass ratio of sugar to DES was 1:40,the conversion of fructose was 69.9±2.01%,the yield of 5-HMF was63.6±1.3%,and the selectivity of 5-HMF was 91.0±1.0%.The conversion of cellobiose was100% and the yield of 5-HMF was 28.4±1.5% after 60 min.4)In the study of 5-HMF separation and TEBAC/FA（1:2）DES recovery,the effects of six extractants such as methyl isobutyl ketone（MIBK）,methyl tertbutyl ether,tetrahydrofuran,ethyl acetate,butyl acetate and Succinic acid diethyl ester on the extraction performance of 5-HMF in TEBAC/FA（1:2）DES reaction solution were systematically investigated.The experimental results show that MIBK has the best extraction efficiency.When the extraction temperature is 35 ℃,the extraction time is 10 min,and the volume ratio of DES reaction solution to MIBK is 1:2,the extraction efficiency is 47.2±1.2%.More importantly,TEBAC/FA（1:2）DES has good recycling performance after 8 times of extraction.Under the best reaction conditions,the conversion of glucose is 100% and the yield of 5-HMF is 30.1±0.8%.The scientific significance and practical application value of this thesis is to propose and confirm that carboxylic acid DES with both solvent and catalytic function has excellent ability to catalyze glucose to prepare 5-HMF,which provides a new idea for the application of DES to catalyze sugars to produce 5-HMF.