Photocatalytic activities for partial oxidation of α-methylstyrene over zeolite-supported titanium dioxide and the influence of water addition to reaction solvent

Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite

A modified zeolite/TiO2 composite (MZTC) was prepared through a method of saturated infiltration and synthesis in situ. The crystalline phase, micromorphology, elementary composition, specific surface area, pore size distribution, chemical bond and band gap variation of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET specific surface area and pore size distribution analysis (BET), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV-vis DRS), respectively. The microscopic characterization results showed that TiO2 was homogeneously dispersed in the structure of zeolite at the nanoscale range, and a strong chemical bond was established between TiO2 and zeolite. The photocatalytic performance of MZTC was evaluated by studying the degradation rate of methylene blue (MB) dye in aqueous solution under UV-light irradiation. The results of the degradation experiment showed that the MB degradation rate of MZTC-2.5 was the highest, reaching 93.6%, which was 2.4 times higher than hydrolysis TiO2 powder (HTOP) containing the same mass of pure TiO2. The MB degradation rate of MZTC-2.5 still maintained 86.5% after five tests, suggesting the excellent recyclability of MZTC-2.5. The possible mechanism of MB degradation was also discussed.

Preparation and characterization of TiO2/HZSM-11 zeolite for photodegradation of dichlorvos in aqueous solution

The TiO2/HZSM-11 materials were synthesized using titanium isopropoxide as a TiO2 precursor and HZSM-11 a medium pore size zeolite with high thermal and chemical resistance as support. The amount of titanium isopropoxide was varied in order to obtain TiO2 concentrations of 3, 10, 20, 30 and 50 wt% in the final material. They were characterized by a series of complementary techniques: X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (DRS), transmittance Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface area of the TiO2/HZSM-11 samples decreased with the increment of TiO2 loading. As result of the increment of the calcination temperature from 450 to 800°C an increase in the size of the anatase crystals was observed. However, the X-ray diffraction patterns of the solids only presented the characteristic peaks of the anatase phase. The catalytic activity of the materials in the photodegradation of Dichlorvos (DDVP) depended on the TiO2 amount the thermal treatment temperature. The sample containing 30% TiO2 calcined at 450°C showed the best catalytic performance and it can be reused without noticeable activity loss during at least four cycles. The catalytic performance was similar to that of the P25 Degussa used as a reference but its separation, recovery and reuse was easier.