Bifunctional Solid Materials Catalyze The Conversion Of Five Or Six Carbon Sugars To Levulinic Acid

Currently,fossil resources was closely related to human social activities.The situation of making use of large quantities of fossil resources has caused greenhouse effect and environmental pollution.Biomass was the only sustainable chemical providing organic carbon resources.As an important widely-used intermediate of transformation into biological chemicals from biomass,Levulinic acid(LA)was obtained from hexose catalyzed by designed functional solid acid catalysts on current many reports.However,the research on the LA production from pentose was rarely reported.5-hydroxymethylfurfural(HMF)dehydrated from hexose easily rehydrated into LA,while LA could be obtained by the hydrolysis of furfuryl alcohol(FUL)reduced by furfural(FAL)originally dehydrated from pentose.If without separated and purified,two kinds of sugars(both pentose and hexose)were directly converted into the same product(LA)in a catalytic system,along with fomic acid(as by-product during hexose-to-LA process)as hydrogen source reduced FAL to FUL during xylose-to-LA process.This reaction system would avoid product separation,thus enhancing selectivity to target compound.Therefore,the following work have been carried out:(1)A series of solid acid catalysts were prepared by a hydrothermal process with doping different metals(Cr,In and Fe),and the structure and properties of catalysts were identified via a series of characterization experiments.The Fe-NbP in catalytic production of LA from glucose exhibited the best catalytic activity.The effect of various reaction parameters such as temperature,time,catalyst dosage,and substrate concentration on LA production has been investigated.Conversion of various carbohydrates to LA catalyzed by Fe-NbP and catalyst recycling under the optimized reation conditions were also tested.It was found that LA yield was 64.2% under the reaction conditions of 0.056 mol/L glucose,32.3 mol % Fe-NbP,10 mL water,3.0 h,and 180 ?The Fe-NbP was also efficient for the transformation of carbohydrates containing fructose and glucose units into LA.The catalyst could be recycled for four times without significant loss of activity.(2)A series of solid acid catalysts were prepared by a hydrothermal process with doping different amounts of copper,and the structure and properties of catalysts were identified via a series of characterization experiments.The Nb P in catalytic production of FAL from xylose exhibited the best catalytic activity.The effect of various reaction parameters such as temperature,time,catalyst dosage,and substrate concentration on FAL production has been investigated.Conversion of xylose to FAL catalyzed by NbP in different reaction systems and catalyst recycling study under the optimized reation conditions were also tested.It was found that FAL yield was 54.9% under the reaction conditions of 0.1 g xylose,0.05 g NbP,10 mL water,3.0 h,and 180 ?The catalyst could be recycled for four times without significant loss of activity.(3)A series of metal sites-solid acid catalysts were designed and prepared.Different kinds of metals,preparation methods and solid acid as catalyst carrier have been also optimized.The structure and properties of catalysts were identified via a series of characterization experiments.The Cu/NbP prepared by incipient wetness impregnation and other catalysts were applied in the production LA from FAL via "a pot two process".The effect of various reaction parameters such as Cu loading,temperature,time,and FA dosage has been investigated.It was found that LA yield was 67% under the reaction conditions of 1 mmol FAL,0.05 g 1.5%Cu/NbP,10 mmol FA,5 mL water,3 h,and 160?.