Experimental And Molecular Simulation Study On Preparation Of Functionalized Mesoporous Carbon Materials And Their Catalytic Performances

Mesoporous carbon materials showed wide application prospect as catalyticmaterials because of their uniform mesoporous structure, high specific surface areaand large pore volume. In this thesis, the mesoporous carbon materials with orderedmesoporous structure were successfully prepared by using of nanocasting method andself-assembly technique in aqueous phase, respectively. The surface functionalizedmethods of mesoporous carbon materials, such as acidity and hydrophobicitymodifications, were systematically studied. The effects of pore structure, surfaceacidity, surface hydrophobicity of mesoporous carbon based solid acid catalysts on thecatalytic esterification of free fatty acids (FFAs) in high acid value oil were alsosystematically investigated. The experimental characterization methods and molecularsimulation were simultaneously used to explore the possible mechanism ofself-assembly process of mesoporous carbon materials.The mesoporous silica was used as template to synthesis mesoporous carbon bynanocasting method; then sulfonated mesoporous carbon solid acid catalyst wasobtained through sulfonation. The nanocasting process, carbonization and sulfonationconditions were systematically investigated. It was indicated that the more uniformpore size distribution and larger specific surface area of mesoporous carbon materialscould be obtained, when sucrose was used as the carbon precursor and through secondnanocasting; the stable Br nsted acid sites, higher acid density, well-ordered andstable mesoporous carbon framework were obtained after carbonization at600℃andsulfonation at160℃for6h. The catalytic activity of the sulfonated mesoporouscarbon catalyst for the catalytic esterification of methanol and FFAs in waste cookingoil was evaluated. The experimental results showed that the FFAconversion of93.8%could be obtained under the optimized reaction conditions, and the acid value ofproduct oil could be reduced to less than2mg KOH/g. The cluster model ofsulfonated mesoporous carbon was constructed, and the adsorption energies and stableconfigurations of esterification concerned reactants and products adsorbed on thecluster were investigated by a density functional theory method. The calculated resultsindicated that methanol was preferred to be adsorbed and interacted with thepre-adsorbed oleic acid, but not with the acidic sites on catalyst surface. The presence of water adsorbed on the sulfonated mesoporous carbon catalyst could result inobvious decrease of adsorption energies of methanol and oleic acid.A series of fluorinated ordered mesoporous carbons (FOMCs) materials withdifferent fluorine content were successfully synthesized by a controllable one-potmethod in the aqueous system. The characterization results showed that the obtainedFOMCs had well-ordered mesoporous structure, higher specific surface area and moreuniform mesopore size; the incorporation of fluorine could improve thehydrophobicity of carbon material. The hydrophobicity of FOMCs was enhanced withthe increasing of fluorine content. When the hydrophilic sulfonyl group-SO3H wasincorporated on the surface of FOMCs material, the rather strong hydrophobicitycould be still remained. The catalytic activities of SO3H-FOMCs catalysts foresterification of FFAs in waste cooking oil were investigated in case of differentcontents of water. It was found that the influence of water content for esterificationactivities was not obvious for the catalysts with higher fluorine content, thus theSO3H-FOMCs catalysts could still maintain their high catalytic esterificationactivities in the presence of water.The self-assembly process of FOMCs in aqueous phase synthesis was simulatedby dissipative particle dynamics method. The calculated results indicated that thehydrophobic side of template agent constructed the characteristic structure ofmesoporous carbon, and the hydrophilic side of template agent and carbon source insystem constructed simultaneously the pore wall of mesoporous carbon. After thehydrophobic side of template agent was removed out, the carbon source in thehydrophilic side of template agent could be transformed to form the microporousstructure on pore wall surface of mesoporous carbon. During the self-assemblyprocess, the content of carbon precursor could affect the thickness and homogeneityof mesopore wall; and water could play a role to disperse carbon source and templateagent in self-assembly system. Moreover, the possible mechanism on preparation ofordered mesoporous carbon materials was suggested, which could provide theunderstanding and knowledge for the synthesis of mesoporous carbon byself-assembly method in mesoscopic scale.