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Preparation, Characterization and Catalytic Oxidation for Cyclopentene of WO_x Catalysts

Author: LuGuang
Tutor: LiXinYong
School: Dalian University of Technology
Course: Water Science and Technology
Keywords: Cyclopentene Glutaraldehyde WO_x H2O2 Hydrocarbons pollutants
CLC: O643.32
Type: Master's thesis
Year: 2008
Downloads: 145
Quote: 1
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Abstract


In this dissertation, the WO3/SiO2 catalyst was prepared by sonication-impregnation combination approach using commercial silica gel as support. Combining with some modern physical methods used to study the crystalline structure, the interaction between support and active constituent, the state of the active constituents on the surface of support, such as X-ray diffraction （XRD）, laser Raman, Fourier transformed infrared spectroscopy （FT-IR）, and X-ray photoelectron spectroscopy （XPS）, and so on. The results indicate that the loading amount of the active constituent and the calcination temperature will influence the crystalline structure, the interaction between the support and the active constituent as well as the state of the active constituent. When the loading amount of the catalyst was more than 15 wt%, or the calcination temperature was higher than 723 K, WO3 crystals would emerge on the surface of support with weakened interaction between the catalyst and the supporter. Besides, low-valenced ion of W5+ existed in the active constituent on the surface of the catalyst.Uniform and micrometer-scaled spherical TiO2 particles were fabricated through the hydrolysis of TiCl4, which was utilized as supporter to prepare highly-dispersed WO3/TiO2 by ultrasonic-impregnation method. Characterizations by SEM, TEM, XRD, laser Raman and XPS were applied to analyze the as-prepared TiO2 and WO3/TiO2.The results show that the TiO2 micro-balls are of anatase crystalline type with diameter of about 3μm. The core-shell structure of WO3/TiO2 possesses a WO3 shell of about 150 nm thickness. After the loading of WO3, the crystalline type and the structure of TiO2 as the supporter did not change. When the loading amount was less than 15 wt%, the tungsten oxide was amorphous. When the loading amount was between 15 wt% and 20 wt%, the tungsten oxide existed in the form of tetrahedron WO42-. But in the case of high loading amount of larger than 20 wt%, the WO3 crystals in octahedron were formed on the surface of TiO2.Cyclopentene was chosen as degradation substrate to investigate the catalytic oxidation activity of WO3/SiO2 and WO3/TiO2. The experimental results show that the catalytic activities of these two systems are similar and both of them can effectively oxidize cyclopentene catalytically. The main factors that affect the degradation of cyclopentene by the tungsten oxide have been analyzed, such as reaction temperature, reaction time, the amount of hydrogen peroxide, solvent species, cocatalyst, silicon gel type, the loading amount of catalyst, the calcination temperature of the catalyst, etc. Meanwhile, the reuse and the regeneration of the WO3/SiO2 catalyst were also examined. At least 5 times of repeated operation could be realized for this catalyst, as confirmed by our experiment.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalytic reaction
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