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Preparation and Physicochemical Properties of Mesoporous Metal Oxides MO_x (M=Cr, Fe, Co, Sm, Eu)

Author: XiaYunSheng
Tutor: DaiHongXing
School: Beijing University of Technology
Course: Environmental Science
Keywords: Hard template method Mesoporous transition metal oxide catalyst Mesoporous rare earth oxides Elimination of volatile organic compounds
CLC: O643.36
Type: PhD thesis
Year: 2010
Downloads: 569
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Abstract

Industrial production, transportation, and housing decoration emit volatile organic solvents, such as aromatic hydrocarbons, alcohols, esters, ketones. Most of the volatile organic compounds (VOCs) atmospheric pollution and endanger human health. Therefore, strict control emissions of VOCs concern. In many methods of elimination of VOCs, the catalytic oxidation method is one of the most effective way to be recognized, and the catalyst is key to the realization of the process. Despite good low-temperature activity of the noble metal catalyst, but its high price limits its wide application. The bulk base metal oxide and a composite oxide of VOCs oxidation shows good catalytic performance, but a lower specific surface area and the lack of developed pore structure, so that the low-temperature catalytic activity of such materials are affected. Therefore, research and development with a high specific surface area and developed pore structure of transition metal oxide catalysts have important theoretical and practical value. The study showed that exhibit good catalytic activity of transition metal oxides such as chromia, iron oxide, and cobalt oxide oxidation of VOCs. In order to further improve its catalytic properties, this paper studied mesoporous chromium oxide mesoporous iron oxide and cobalt oxide mesoporous template preparation method using nitrogen adsorption desorption (BET), X-ray powder diffraction (XRD), X-ray photoelectron spectra (XPS), ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR) spectrophotometry, transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA), temperature programmed reduction (TPR) techniques to characterize these mesoporous materials the physicochemical properties, and to evaluate their the oxidized catalytic activity typical of VOCs (e.g., toluene, formaldehyde, methanol, acetone and ethyl acetate). In addition, the article also mesoporous oxide samarium, and mesoporous europium oxide, Synthesis and Characterization of research work. Results mainly in the following four aspects: 1, three-dimensional ordered mesoporous silica (KIT-6) as a hard template, free solvothermal method and ultrasound-assisted Preparation of ordered mesoporous chromium oxide. The results show that the the resulting chromium oxide has a high specific surface area (106 ~ 124 m2 / g), and three-dimensional ordered mesoporous structure, excellent low temperature reduction performance, a variety of oxidation states of chromium coexistence and rich surface oxygen species. Chromia prepared since the autoclave constant temperature treatment at 240 oC mesoporous (meso-Cr-240) by solvothermal oxidation of toluene and ethyl acetate (airspeed = 20000 mL / (GH), toluene or acetic acid The best catalytic activity of the ethyl ester concentration = 1000 ppm), the conversion was 90% when the temperature is 234 oC and 190 oC and the apparent activation energy of 79.8 kJ / mol and 51.9 kJ / mol, respectively. By ultrasound-assisted method in of 400 oC ignition resulting mesoporous chromia (meso-CR-400) of the catalytic activity of formaldehyde, acetone and methanol oxidation (airspeed = 30000 ml / (GH), the VOC concentration = 500 ppm) the best, the conversion was 90% when the temperature was 117 oC to 124 oC and 130 oC, corresponding to the apparent activation energy of 45.6 kJ / mol, 49.7 kJ / mol and 50.8 kJ / mol. 2, respectively, using a three-dimensional ordered mesoporous KIT-6 hard template vacuum impregnation method and citric acid (CA) auxiliary prepared by thermal decomposition of iron oxide and wormhole like mesoporous iron oxide. The results show that the ignition temperature of 400 oC, the resulting three-dimensional ordered mesoporous iron oxide (Fe-KIT6-400) and worm-like mesoporous iron oxide (Fe-CA-400), the highest specific surface area 113 m2 / g and 165 m2 / g. Fe-CA-400 has the best low temperature reduction, and the highest surface oxygen concentration. When the space velocity was 20000 mL / (gh), acetone and methanol conversion was 90% when the temperature of the Fe-CA-400, respectively, as low as 186 oC and 189 oC, the apparent activation energy of 70.7 and 60.9 kJ / mol, . 3 mesoporous silica KIT-6 and SBA-16 hard template, vacuum impregnation method to prepare a three-dimensional ordered mesoporous cobalt oxide (Co-KIT6 and Co-SBA16). The results show that the pore structure of the resulting cobalt oxide and the pore structure of the template, and a specific surface area of ??the two were 121 m2 / g and 118 m2 / g and have excellent low temperature reduction performance and the surface oxygen species when airspeed = 30000 mL / (gh), VOC concentration = 1000 ppm, CO-page KIT6 catalytic activity than the catalytic activity of the Co-SBA16 slightly better. Toluene and methanol in Co-KIT6, on conversion of 90% when the temperature is 190 oC and 139 oC, and the apparent activation energy were 59.9 and 50.1 kJ / mol. 4, samarium nitrate and nitric acid europium metal source, respectively, using a hard template synthesis of surfactant assisted sol - gel method and ultrasound-assisted nano-and mesoporous samarium and europium oxide. Results show that class spheroplasts Sm2O3 Eu2O3 nanoparticles THF surfactant resulting product, a specific surface area of ??44-49 m2 / g the resulting product of the surface-active agent; polyvinylpyrrolidone coryneform Sm2O3 Eu2O3 nanoparticles specific surface area of ??34 ~ 37 m2 / g. By the the ultrasonic assisted KIT-6 as hard template system had ordered mesoporous Sm2O3 and Eu2O3 specific surface area of ??up to of of 134 ~~ 166 m2 / g. Nano-and mesoporous samarium and europium oxide have a strong absorption in the ultraviolet region, which is related to its surface morphology and crystal structure.

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