Preparation And Catalytic Property Of Monodisperse Titania Microsphere

Monodisperse titania microspheres was prepared by low temperature reflux andsolvothermal methods from tetrabutoxytitanium. Obtained samples have large specificsurface area，high photocatalytic activity and mesoporous structure, they can beutilized extensively in the areas of sewage treatment,air purification and self cleaningmaterials as a type of effective photocatalyst material. The following works have beendone in the thesis:1. Amorphous TiO₂precursor was parpared via sol gel stratiogy withtetrabutoxytitanium as the raw material, TEA as the coordination agent, then TiO₂precursor was treated by reflux and solvothermal methods to crystallization, finallymonodisperse titania microspheres was obtained.2. XRD, SEM, BET and TG was used to characterize the crystal structure,morphology and thermal stability of prepared TiO₂samples. Their photocatalyticactivities were evaluated by decomposition of Cr （VI） in solution. The results showedthat TiO₂samples prepared by reflux method were microspheres with good dispersityand anatase was the main crystal phase. The particle size was in uniform and there’sno adhesion of particles was found. Samples prepared by solvothermal methodpresented anatase and rutile crystal phase. The obtasined particle was near sphere withroughness surface and their size was not in uniform because some particles stickedtogether. The micropheres break down into hollow structures when the reactioncondition is changed. Mesoporous structure was confirmed by BET analysis in twokinds of samples and the solvothermal samples have larger specific surface area. Theas prepared micropheres presented highly temperature stability in TG DSC analysisand excellent catalytic activity in the photocatalytic reduction process of Cr （VI） withthe removal ratio above90%in2h.3. The effects of reaction solvent, concentration of HCl, reaction temperature andtime on the structure, morphology and photocatalytic activity of TiO₂microsphereswere studied. The results showed that the obtained samples have more uniformparticle size and better dispersity when HCl/EtOH was used as the reaction solvent. Inthe solvothermal process, the acid concentration has a significant effect on phase. Therutile content in the TiO₂samples reached extremum when the concentration of acid is 5wt%. The micropheres broken down into hollow structures when the concentrationof acid increased to a certain extent. In the reflux and solvothermal methods,increasing reaction temperature and prolonging reaction time could improve thedegree of crystallization. Severely agglomeration emerged when the reactiontemperature is too high or the reaction time is too long. When3wt%HCl/EtOH isused as refluxing solution, the sample obtained under85℃for2.5h has the bestdispersion and catalytic performance, and The removal ratio of Cr（Ⅵ）reached to99%in2h.4The effect of different crystallization methods（reflux, solvothermal andcalcination）on the property of TiO₂nanomaterials was studied. The results showedthe calcined sample under high temperature possessed the highest crystallizationdegree but particles agglomerate severely. Their photocatalytic activity is lower thanthat of reflux and solvothermal samples. The low temperature reflux method wasfound to be the most appropriate one for preparing monodisperse TiO₂microspheresmesoporous materials.