Photocatalytic Epoxidation of Propylene with Bi<sub>2</sub>WO<sub>6</sub>-Based Catalyst Supported on Glass Beads (original) (raw)
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The present paper analyses the preparation and characterisation of different titanium dioxide-based photocatalysts for propene oxidation at low concentration. Special attention has been paid to the agglomeration of the photocatalysts in form of pellets, to the study of the effect of introducing some carbonaceous materials into the catalyst composition and to comparison with commercial photocatalysts. Our results show that P25 exhibits the best activity among all the studied materials. However, activity importantly decreases when agglomerating the photocatalysts in form of pellets, either with or without carbon addition. The type of carbon material used in the photocatalyst strongly affects propene activity. Thus, carbon materials combining high surface area and high electric conductivity enhance the photocatalyst performance and photocatalyst pellets have been prepared exceeding the activity of a carbon-containing commercial photocatalyst. The importance of the UV-source has been highlighted, showing the 257.7 nm peak radiation much better results than the 365 nm UV-light. The studied photocatalysts are very interesting for propene oxidation not only because of their high activity, but also because it remains constant for more than 40 h and total mineralization of the oxidised propene to carbon dioxide and water is achieved.
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DESALINATION AND WATER TREATMENT, 2020
In this article, a solution of methylene blue (MB) was submitted to a photocatalytic process, was used as the basis for studies of more complex compounds such as the effluents from universities' laboratories. MB is a standard compound for many photocatalytic tests. The use of commercial titanium dioxide (TiO 2) in degradation of toxic compounds is very suitable as it is a cheap and effective. Therefore, its characterization confirmed that its physicochemical properties fit this purpose. TiO 2 particles were characterized by X-ray fluorescence (XFR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and particle size analysis. The chemical composition of titanium dioxide by XFR was 98.6% pure. Through XRD, it was possible to realize that TiO 2 presented the anatase and rutile crystalline phases, with predominance of the anatase phase. By FTIR, two TiO 2 characteristic bands were found at 505 and 612 cm-1. By SEM, it was visualized that TiO 2 had a structure with uniformly distributed spherical particles. The particle size distribution of TiO 2 presented a mean diameter of 2.23 μm. The effluent degradation process was evaluated by photolysis and photocatalysis. In the degradation process of MB by photolysis, a maximum efficiency of 15% was obtained with the use of three irradiation intensities. In the photocatalysis process, it was observed that in pH = 10.0 and initial MB concentration of 2.0 μmol L-1 , the photodegradation was higher. This is due to the surface of TiO 2 particles in alkaline medium and to the presence of photocatalysts promoting the formation of hydroxyl radicals, resulting in efficiency greater than 93.0%. Therefore, the ultraviolet (UV) treatment process caused a smaller reduction in MB degradation, while the UV/TiO 2 technique was more efficient, presenting potential for this application.
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Monatshefte f�r Chemie/Chemical Monthly, 2004
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