Photocatalytic removal of nitrogen oxides from air on TiO2 modified with bases and platinum
Autor: | N. N. Tolkachev, Galina N. Baeva, A. Yu. Stakheev, B.N. Shelimov, V. B. Kazanskii |
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Rok vydání: | 2011 |
Předmět: | |
Zdroj: | Kinetics and Catalysis. 52:518-524 |
ISSN: | 1608-3210 0023-1584 |
DOI: | 10.1134/s002315841104015x |
Popis: | The efficiency of TiO2 (Degussa P-25) modified with an alkaline admixture (urea, BaO), sulfuric acid, or platinum in the photocatalytic oxidation of NO (50 ppm) with a flowing 7% O2 + N2 mixture under UV irradiation in a flow reactor at room temperature and atmospheric pressure is reported. Because of the progressive blocking of active sites of the photocatalyst by the reaction products (NO2, NO3−), it is impossible to realize prolonged continuous removal of NOx (NO + NO2) from air without catalyst regeneration at elevated temperatures. The efficiency of the photocatalysts is characterized by specific photoadsorption capacity (SPC) calculated from the total amount of NOx adsorbed during 2-h-long irradiation. Modification of TiO2 with 5% BaO or 5% urea raises the SPC of the catalyst by a factor of 2–3. Presumably, this promoting effect is due to the basic properties of these dopants, which readily sorb NO2 and NO3−. A considerable favorable effect on SPC is also attained by adding 0.5% Pt to (5% BaO)/TiO2. The SPC of the (0.5% Pt)/TiO2 catalyst depends on the state of the platinum. The samples calcined in air at 500°C, which contain Pt+ and Pt2+, have an approximately 2 times higher SPC than unpromoted TiO2 and ensure a much larger NO2/NO ratio at the reactor outlet. Conversely, the samples reduced in an H2 atmosphere at 200°C, whose platinum is in the Pt0 state, show a lower SPC than the initial TiO2 and cause no significant change in the NO2/NO ratio. |
Databáze: | OpenAIRE |
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