Catalytic Conversion Of Hexose To 5-HMF At Low Temperature

The increasing consumption of fossil resources such as coal,oil and natural gas in the field of energy utilization and chemical production has led to a large number of greenhouse gas emissions into the atmosphere,which has caused serious harm to the ecological environment.In today’s"carbon neutral"development background,it is urgent to reduce greenhouse gas emissions,which also promotes the innovative development of green and sustainable alternative energy in the"post oil"era.Biomass resources mainly refer to lignocellulose in plants,including carbohydrates,lignin and lipids.It is a promising alternative raw material.Biomass is the only available and renewable carbon source,which has the property of carbon neutralization.The synthesis of high-value liquid fuels and high-value chemicals（especially lignocellulosic biomass）from biomass has become the focus of research in this field.5-hydroxymethylfurfural（5-HMF）is an important multi-purpose biologically derived furan platform compound.HMF contains a variety of functional groups and has broad potential availability.It can be effectively transformed into a variety of value-added derivatives.It is an ideal renewable substitute for fossil fuels.5-HMF can be obtained by selective removal of three molecules of water from six carbon sugars represented by fructose and glucose.These six carbon sugars are renewable biomass resources.Therefore,the process of catalytic synthesis of 5-HMF from biomass is in line with the concept of"carbon neutralization"and sustainable development,and is attracting more and more research attention.This paper mainly carried out some research work on the effective conversion of fructose and glucose to 5-HMF at low temperature.The main research contents include:（1）A series of metal chlorides were used as catalysts to catalyze the conversion of fructose to 5-HMF at low temperature.The suitable catalysts were selected.The effects of catalyst dosage,fructose addition,cocatalyst,cosolvent,reaction temperature and reaction time were investigated,and the recycling and possible mechanism of the catalyst were explored.The results showed that with 30 mg fructose as raw material and Nb Cl₅ as catalyst,500μL dimethyl sulfoxide（DMSO）was used as solvent,the amount of Nb Cl₅was 15%of the molar amount of fructose,and the conversion of fructose and the 5-HMF yield could reach 97%and 75%respectively at 50℃for 240 min.Nb Cl₅ is recyclable in the reaction system.Nb Cl₅ may catalyze the fructose reaction through the synergistic action of Br（?）nsted acid and Lewis acid,which mainly acts with the hydroxyl and carbonyl groups at the end of fructose.The reaction system is also suitable for the conversion of inulin to 5-HMF at low temperature.（2）5-HMF was prepared by glucose conversion in DMSO solvent with2-carboxyphenylboronic acid（2-CPBA）catalyst and metal chloride as cocatalyst.The results show that the mixed catalyst of 2-CPBA/metal chloride can effectively catalyze the conversion of glucose to 5-HMF under mild conditions（the reaction temperature is80℃）.Using 2-CPBA and Nb Cl₅ as catalysts,glucose was reacted at 80℃for 360 min.the glucose conversion was 98%and the 5-HMF yield was 58%.The catalytic system is recyclable.The catalyst mainly interacts with the carbonyl group at the glucose end.The reaction system is also suitable for the conversion of other carbohydrates to 5-HMF at low temperature.