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Catalytic Oxidation of Formaldehyde at Low Temperature over Supported Nano Gold Catalysts

Author: LiHongFang
Tutor: LuJiQing；LuoMengFei
School: Zhejiang Normal University
Course: Physical and chemical
Keywords: Au catalyst Formaldehyde Catalytic Oxidation Ceria Oxygen deficiency
CLC: O643.36
Type: Master's thesis
Year: 2010
Downloads: 94
Quote: 0
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Abstract

Formaldehyde is one of the most serious pollutants in indoor, high toxicity and release of years long. Long-term residence in the environment containing formaldehyde easily lead to serious health problems, and therefore, how to eliminate indoor formaldehyde pollution has become one of the focus of attention. In many elimination of formaldehyde method, catalytic oxidation technology at lower temperatures formaldehyde converted into nontoxic CO2 and H2O, is an effective way to eliminate formaldehyde. A hot research topic in the field is a low-temperature oxidation of formaldehyde on supported Au catalysts, their research focus has been on how to further improve the performance of low-temperature oxidation of formaldehyde Au catalyst. In addition, the Au catalyst on the reaction mechanism, as well as factors affecting the activity there are still a lot of controversy. In this study, deposition - precipitation method to prepare a variety of supported Au catalysts investigated carrier of the Au catalysts formaldehyde oxidation performance, and to explore the interaction between Au and carrier; mainly inspected Au/CeO2 catalyst Au morphology and valence , oxygen deficiency on the catalytic properties, and preliminary reaction mechanism of formaldehyde oxidation of the Au catalyst. The main content of the research in this paper and the main results obtained are as follows: the Au loading Au/CeO2 catalyst on formaldehyde catalytic oxidation. The Au particles Au/CeO2 catalyst with increasing Au loading and grew up, which directly affects the Au catalyst formaldehyde oxidation activity. Au loading of 2.52%, Au/CeO2 catalyst has the highest catalytic activity, and 150 ° C formaldehyde completely converted to H2O and CO2. Au loading of 2.52%, the catalyst is not only more active sites, and few reunion between the Au particles. Carrier type of the Au catalytic oxidation of formaldehyde. By deposition - precipitation method and ammonia complexation prepared the four carrier (Al2O3, TiO2, CeO2 and SiO2) nano-Au catalyst load, investigated formaldehyde catalytic oxidation activity. The experimental results show that, 2.30Au/CeO2 showed the best catalytic performance of the catalyst at 40 ℃ the formaldehyde conversion rates above 80%. Formaldehyde catalytic oxidation activity by Au chemical state and carrier nature. 2.30Au/CeO2 catalyst exhibits low-temperature activity is likely related to the plasma state Au species simultaneously AuxCe1-xO2-δ solid solution formation of a large amount of oxygen deficiency, to improve the oxygen activation and also helps promote the catalyst activity at low temperatures. 3. CeO2 the carrier specific surface area of ??the Au catalyst. Templating agent and sol - gel preparation different than the surface area of ??CeO2 carrier, by deposition - precipitate prepared a Au/CeO2 catalyst, to examine the impact on the the Au catalytic oxidation of formaldehyde of CeO2 carrier specific surface area. The experimental results show that, with the formaldehyde oxidation the carrier specific surface area increases, Au/CeO2 catalyst activity gradually increased. Raman spectroscopy showed that the high specific surface area of ??the Au catalyst contains a higher concentration of oxygen vacancies, XPS and TPR results prove the catalyst in the presence of a large number of Au, Au3 ions, and these two factors help to promote the adsorption and oxidation of formaldehyde. The high specific surface area Au/CeO2-270 catalyst (specific surface area of ??270 m2 / g) having a good activity on the catalytic oxidation of formaldehyde can be below 50 ℃ formaldehyde completely eliminated, this catalyst for the development practicality room temperature to eliminate formaldehyde to provide guidance. Possible mechanism of 4. Au/CeO2 catalytic oxidation of formaldehyde. Studied by in situ infrared diffuse reflectance spectroscopy Au/CeO2 possible mechanism of the catalytic oxidation of formaldehyde: Formaldehyde first Au/CeO2 catalyst, adsorption, and then react with the activated oxygen, to generate carbonate in the form of the intermediate product, followed by dissociation for gaseous CO2 and H2O.

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