Studium přípravy oxidů kovů na bázi Ti a Zr pomocí přetlakových a superkritických tekutin využitelných k redukci znečištění životního prostředí

Abstract

This bachelor thesis deals with preparation of Ti and Zr based oxides by using pressurized (subcritical) and supercritical fluids (water and methanol) and their physico chemical characterization. The thesis is composed of the theoretical part, the experimental part and results with discussion. Within the theoretical part the properties and application of TiO2, Zr and ZrO2 are described and the importance of TiO2 doping with zirconium is explained. In the theoretical part, the properties and behavior of supercritical and pressurized fluids, the state of the art of preparation of Ti and Zr based oxides using pressurized and supercritical fluids and the principles of characterization methods are reported as well. The experimental part of the thesis is focused on the description of Zr0,1Ti0,9On mixed oxide preparation and its catalytic testing in photocatalytic oxidation of model azo-dye Acid orange 7. Within the results and discussion the results of characterizations of prepared materials and the effect of individual preparation parameters by using pressurized water and pressurized/supercritical methanol on the purity, textural and structural properties and photocatalytic activity of prepared Zr0,1Ti0,9On mixed oxide are presented and discussed. The preparation of Zr0,1Ti0,9Ongel precursor was carried out using a sol-gel method controlled in a reverse micellar environment of nonionic surfactant Triton X-114 in cyclohexane. The gel precursor was then processed in pressurized water and pressurized or supercritical methanol. The effect of volume of used water, temperature and pressure on the purity, textural and structural properties of Zr0,1Ti0,9On mixed oxides for the photocatalytic degradation of the model azo-dye Acid orange 7 was investigated. Organic elementary analysis, nitrogen physisorption, Raman spectroscopy and UV-Vis spectroscopy were used for characterization of physico-chemical properties of prepared materials. It was revealed that water amount and pressure had negligible effect on the crystallization (structure) of Zr0,1Ti0,9On which was confirmed by textural results. However both mentioned parameters affected the purity of prepared Zr0,1Ti0,9On. The temperature showed significant effect on purity, structure and texture which was manifested in increased photocatalytic activity of Zr0,1Ti0,9On. The optimal preparation conditions of Zr0,1Ti0,9On mixed oxid were determined to be 100 °C, 20 MPa, 2 l of water and 0.25 l of methanol (i.e. processing in pressurized water and pressurized methanol).