Study Of Preparation Of Metal-modified Mesoporous Molecular Sieve And The Application For Photocatalytic Epoxidation Of Styrene

The mesoporous molecular sieve SBA-15were reported to have attractedconsiderable attentions since its advent due to their outstanding properties, such as largespecific surface area, highly ordered pore structure, uniform and tunable pore size,narrow pore size distribution, containable pore wall thickness, facile modification ofsurface properties and well hydrothermal and high thermal stability and so on. Owing tothese excellent characteristics, mesoporous molecular sieve as a good catalyst carrier hasopened a new era of molecular sieve and were widely utilized in the fields of catalysts,adsorption, separation, environment and nano-materials and drug delivery etc. However,the framework of pure-silica mesoporous SBA-15is mainly consist of amorphous SiO2,its surface is inert and lacks of active sites, in addition, the framework has no defects, theelectrical neutrality and has no acid sites on the surface, therefore, they show poorcatalytic performances. In order to solve this problem, mono/double substituted sievewere designed and synthesized to broaden the application of SBA-15in catalytic domainby introducing Lewis acid&Br nsted acid sites and oxidation&reduction centers aswell as the active species. The main research contents and results were summarized asfollows:1. Preparation, characterization and photocatalytic applications ofLn-Ti/APTES-SBA-15(Ln=La, Ce, Sm, Eu) composite photocatalyst. The acid-basecooperative function materials of APTES-SBA-15were prepared by a post-synthesisgrafting process employing SBA-15as the carrier and3-aminopropyltriethoxysilane(APTES) as the coupling agent. The reaction were taken place under a nitrogenatmosphere and non-aqueous media, the silicon hydroxyl surface of mesoporousmaterials were substituted by amino-group. Then using aminopropyl functionalizationmaterials as supporter and titanium as the main component elements, followed by addingthe second auxiliary component lanthanide metal (La, Ce, Sm, Eu), theLn-Ti/APTES-SBA-15composites catalysts that have the redox functional were preparedand characterized by XRD, FT-IR, UV-vis, SEM and TEM. Subsequently, thephotocatalytic activity of catalysts were evaluated through the epoxidation of styrene. Through changing the conditions of experiment, the various parameters that influencingthe reaction such as metal loading, the amount of catalyst, mole ratio of H2O2to styreneand reaction time were investigated. During the reaction, hydrogen peroxide (H2O2,30%)played as oxidant, and in the presence of titanium and europium double metal substitutedon amino-functionalized SBA-15, referred to as Eu-Ti/APTES-SBA-15catalystsexhibited high catalytic activity, especially europium/titanium was equal to2, thecatalytic activity reached a maximum value.2. Synthesis, characterization and study on photocatalytic of Au/APTES-SBA-15composite catalyst. The small size of gold-based highly dispersed catalysts whichpossess high activity and selectivity were prepared by impregnation method served as theAPTES-SBA-15as carrier and HAuCl4as gold sources, which using the static interactionbetween the amino group and chloroauric acid. The synthesized materials werecharacterized by X-ray diffraction, FT-IR, UV-vis, transmission electronmicroscope(TEM), scanning electron microscope(SEM) and EDS etc. The conversionrate of composite catalyst2%Au/APTES-SBA-15can reach41.03%, furthermore,amino-group has a decisive effect on the synthesis of gold-based catalysts with small sizeand highly dispersed gold nanoparticals.3. Preparation, characterization and the analysis of photocatalytic performanceof Nb-Ti-SBA-15composite catalyst. The double metal niobium-and titanium-containing mesoporous molecular sieves based on the high-surface area silica supportsSBA-15structure were synthesized by impregnation method using Nb2O5as niobiumsource(before use it was dissolved in oxalic acid solution)and tetrabutyl titanate astitanium source, respectively. In the catalyst, titanium as the main active component thathas a redox function points and transition metal Nb as the second auxiliary componentwere loaded on the channels of mesoporous molecular sieves. Through adjustingdifferent mental loading, to find the best component content. In the photocatalyticreaction that employing hydrogen peroxide (H2O2,30%) as oxidant, by addition of smallamount of H+into the reaction system could dramatically enhanced the conversion ofstyrene and the selectivity to styrene oxide. In addition, the presence of niobium and titanium could increase the acid sites of molecular sieves, and then influence the catalyticactivity, the synergistic effect of two metals were performed most incisive performancein this experiment.