Study On Preparation Of 5-Hydroxymethylfurfural From Corncob Liquefaction Under Microwave

The reduction of fossil fuels has stimulated the development of sustainable utilization of resources.As a renewable and multi-purpose carbon source,biomass energy is regarded as an ideal substitute for fossil resources and the production of high value-added chemicals.5-hydroxymethylfurfural（HMF）is an important platform compound for converting biomass into furan chemicals.Because of its great potential in the field of chemical manufacturing,it is known as the"sleeping giant".However,due to the stable structure and difficult hydrolysis of biomass,the yield of HMF is very low,and the existing conversion methods still have some shortcomings,includingequipment corrosion,low energy utilization and serious pollution.Therefore,a supported sulfonated hydrothermal carbon based catalyst（x/HSC）for biomass microwave-assisted liquefaction was prepared to enhance the hydrolysis efficiency of corncob and the conversion of monosaccharide HMF.Through the study of reaction conditions and kinetics,the reaction kinetics behavior and related mechanism of the carbon based catalyst in the reaction process were revealed,which realized the sustainable value-added utilization of cellulose biomass and alleviated the pressure caused by the shortage of fossil resources.The main contents of this paper include the following three aspects:（1）In the firststep,glucose was used as the raw material for preparation of sulfonated hydrothermal carbon via one step hydrothermal carbonization method, then the supported sulfonated hydrothermal carbon catalyst was prepared by precipitation method.The physicochemical properties of the catalyst were characterized by XRD,BET,TEM,FT-IR,EDS,SEM,NH₃-TPD and total acid measurement.FT-IR result indicated that aromatic carbon was formed via dehydration,aromatization and polymerization during glucose hydrothermal carbonization.And the outer layer was further dehydrated to form massive coke,thus forming a porous structure under the performance of sulfuric acid and mild condition（120℃）.This kind of molecular structure with aromatic carbon can achieve rapid heating and increase heating rate in the process of microwave-assisted heating,thus saving energy and time cost.In addition,the introduction of active components on the surface of the catalyst improved the content of the catalyst Br?nsted Acid,it was worth noting that the metal content was closed to 10 wt.%,suggestingthat the use of precipitation method can make the metal utilization rate higher on this kind of carbon based catalyst,and the acidity analysis showed that HPW/HSC owned super acidity,which was more conducive to the hydrolysis of biomass and the catalytic conversion of monosaccharide.（2）The supported sulfonated hydrothermal carbon materials were used as catalysts in microwave-assisted catalytic liquefaction of corncob to prepare HMF.The effects of raw material pretreatment,active components of catalyst,reaction time,reaction temperature,microwave input power and catalyst cycle on corncob conversion and HMF yield were investigated.The results showed that the yield of HMF was 59.23 mol%under the conditions of corncob powder particle size less than100 mesh,the use of water and HPW/HSC as solvent and catalyst,respectively,T=180℃,t=60min,input power=250W.After five cycles,the yield of HMF was only 14.14%lower than that of the first cycle,and the XRD characterization of the catalyst after five cycles revealed that the catalyst had almost no change and still maintained good catalytic activity,indicating that the catalyst had good stability,indicating that the catalyst had a good prospect of industrial application.（3）In order to further study the catalytic performance of HPW/HSC catalyst in microwave-assisted liquefaction of corncob to prepare HMF,the kinetic data and mechanism forsynthesis of HMF were obtained and analyzed by two reaction systems with or without catalyst under microwave-assisted heating,and the hydrolysis amount of corncob and yield of HMF were obtained under suitable reaction temperature and reaction time.According to the Arrhenius equation,the dynamic model was established and the dynamic research was carried out.The results showed that the two reaction systems were in accordance with the first-order kinetics under microwave assistance,and the addition of HPW/HSC catalyst can effectively reduce the activation energy（60 k J/mol）.HPW/HSC catalyst had and obvious effect on corncob conversion.During the reaction,Br?nsted Acid can affect the conversion of glucose,Lewis acid can catalyze the formation of HMF,and carbon based support can effectively protect HMF from decomposition.