Research On The Dehydration Of Fructose To 5-Hydroxymethyl Furfural Catalyzed By Graphite Derivates As The Catalysts

In recent years, the increasing depletion of fossil fuels causes the serious energy crisis and environrnental pollution which is bringing harm to the people ’s lives. Thus, developing the renewable biomass resources becomes more and more important now. Research shows that chemical conversion of biomass feedstock is a useful method to produce the high value-added pharmaceutical intermediates and monomer of polymer from sustainable resources. Therein, the catalytic dehydration of 6-C sugar biomass can generate 5-hydroxymethylfurfural(5-HMF), and then to prepare useful compounds such as pharmaceutical products, fuel and polymer through the hydrogenation, oxidation, halogenation, hydrolysis, esterification and aldol condensation reaction.In this thesis, the dehydration of hexoses to 5-HMF catalyzed by graphite-derived solid acid catalysts has been studied. The preparation of the high catalytic activity and stability of metal- free solid catalysts are mainly investigasted, and their catalytic performances on the dehydration reaction are studied in detail.Firstly, the solid acid catalyst graphite oxide(GO) was prepared with a modified Hummers’ method, and then is further employed to the catalytic dehydration of fructose.As a result, it was found that the optimum amount of catalyst GO is 0.1g, the optimum reaction temperature is 120 ℃, the optimum reaction time is 3.5 hours, the optimum reaction solvent is dimethyl sulfoxide. Under the optimal conditions, the yield of 5-HMF arrives at 60.6%. Moreover, GO was further treated by high temperature and strong base/acid, which are respectively denoted as h-GO and n-GO,their catalytic performances are simliar with that of GO in the dehydration, and the yield of 5-HMF is 63.0% or 61.8%, respectively. O n the other hand, the dehydration of inulin catalyzed by the graphite oxide GO was also studied. The optimal reaction temperature is 160 ℃, the optimum reaction time is 4.0 hours and the optimum reaction solvent is H2O:THF(V:V)= 1:3; It was found that a 61.2% yield of 5-HMF is obtained under the suitable conditions.Secondly, the composite polyaniline- graphite oxide(PANI-GO) is prepared from in situ polymerization of aniline in the colloidal GO solution. Futhermore, the sulfated PANI-GO(SO42-/PANI-GO) is also prepared via the sulfation process using a 70% concentrated sulphuric acid. When these materials are used as the catalysts for the D- fructose dehydration, it was found that the PANI-GO and SO42-/PANI-GO exhibits prominent activities, in which 80.7% and 72.4% yields of 5-HMF are obtained in N-methylpyrrodinone solvent. In addition, the effects of reaction temperature, reaction time, the solvents and the recycling of PANI-GO catalyst were also investigated. Finally, the corresponding structures of solid acid catalysts have been characterized by traditional techniques such as FTIR, XRD, BET, TG, SEM and TEM, etc. Also, the related analysis of the catalytic reaction mechanism based on the characterization results is presented in this thesis.