Catalytic Conversion Of Carbohydrates Into5-hydroxymethylfurfural In Ionic Liquid

The seriousness of energy security and environmental pollution has led tothe exploration of alternatives for fossil resources to supply chemicals andenergy. Biomass is the only sustainable source of organic carbon currentlyavailable on earth, and it is considered to be the most promising sustainablesubstitute for petroleum. Renewable and vastly abundant biomass is apromising alternative for the sustainable supply of precious intermediates andplatform chemicals. Carbohydrates make up the majority of biomass, and it ispivotal to develop more efficient and environmentally friendly methods toconvert carbohydrates into useful chemicals.The preparation of5-hydroxymethylfurfural (HMF) from biomass-basedsugars is an important way to the utilization and conversion of biomass energy.HMF is the most ideal biomass-derived platform chemical which has beenrecognized as a versatile and key precursor for the production of biofuels, finechemicals, polymeric materials and solvents and an important intermediate forthe production of fuels and chemicals from sustainable biomass. Nowadays,HMF is usually prepared from fructose, and as the cost is high, it is difficult torealize the industrialization. However, the biomass resources such as celluloseand sucrose are more abundant, therefore, the conversion of biomass-basedcarbohydrates into HMF has practical significance.The contents and results of this research include the following two parts: 1. Catalytic conversion of cellulose into HMF by CrCl₃. Two heatingmodes including microwave irradiation and oil bath heating were used, theeffects of catalyst type and amount, microwave power or reaction temperatureand reaction time on HMF yield were studied, and the two heating modeswere also compared. The results showed that:(1) under microwave irradiation,CrCl₃was found to be the most effective catalst among lewis acids(metalhalides), inorganic acids and solid acids, leading to the yield of HMF up to60%with cellulose (0.1g) and CrCl₃(6mol%, based on the glucose units incellulose) in [BMIM]Cl (1.0g) under microwave irradiation at300W for7min.(2) by oil bath heating, the yield of HMF only reached23%after4hoursat130℃.(3) by comparing the two heating modes, it is found that microwaveirradiation can not only shorten the reaction time greatly, but vastly improvethe yield of HMF. As a new type of efficient and environmentally friendlyheating processs, microwave irradiation will be more and more widely appliedto chemistry research.2. Catalytic conversion of glucose and sucrose into HMF by solid acidand base. The effects of catalyst type, catalyst amount, reaction temperatureand time on HMF yield were studied, and the catalytic performance of thecatalytic system containing ionic liquid and solid catalysts over five repeatedruns was also investigated. The results showed that:(1) the cation exchangeresin Amberlyst-15and anion exchange resin717as the combination catalystsof solid acid and base, exhibited efficient catalytic activity on the conversionof glucose and sucrose to HMF in [BMIM]Cl, leading to the yields as high as51%and63%, respectively;(2) the mechanism of the conversion of glucose toHMF was confirmed with the isomerization of glucose into fructose catalyzedby solid base followed by the dehydration of fructose into HMF by solid acid; (3) as for the glucose, the yield up to51%could be obtained with glucose(0.2g) and cation exchange resin (0.1g) and anion exchange resin (0.2g) in[BMIM]Cl (2.0g) at120℃for20min;(4) as for the sucrose, the yield up to63%could be obtained with sucrose (0.2g) and cation exchange resin (0.1g)and anion exchange resin (0.1g) in [BMIM]Cl (2.0g) at130℃for15min;(5)taking glucose as an example, the catalytic system displayed stable acticityover five repeated runs.