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The Effect of Oxygen Vacancy Concentration on the Properties of Perovskite-type Catalysts

Author: ZhouKeBin
Tutor: WangDao；WuShaoHua
School: Beijing University of Technology
Course: Environmental Engineering
Keywords: Perovskite -type catalyst Oxygen vacancy concentration Catalytic properties
CLC: O643.3
Type: Master's thesis
Year: 2000
Downloads: 247
Quote: 0
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Abstract


In this paper, coprecipitation of the two series of perovskite -type catalyst LaCo 0.5 Fe 0.5 O 3-λ and LaCo 0.47 Fe 0.47 Pd 0.06 O 3-λ (λ is defined as the concentration of oxygen vacancy ) . At different temperatures for the oxidation or reduction of the catalyst pre- prepared with different concentrations of catalyst oxygen vacancy . Investigated catalysts CO, HC and NO catalytic activity , and using XRD, ICP-AES, BET, surface excess oxygen (SEO), TPR and XPS characterization of its research methods to explore the oxygen vacancy concentration on the catalytic activity , structure, , surface excess oxygen and the influence of lattice oxygen activity . Perovskite -type catalyst by reduction , the oxygen vacancy concentration increases , the surface excess oxygen also increases the catalytic activity for CO oxidation , also will be significantly improved, but the HC oxidation catalytic activity is not obvious. Catalyst by oxidation , the oxygen vacancy concentration was reduced , the surface excess oxygen treatment temperature increases with the increase in the catalytic activity for CO oxidation is also increased accordingly ; also the HC oxidation catalytic activity is not obvious. Perovskite -type catalyst by oxidation treatment, the surface Co element enrichment , which can be explained by the oxidation treatment, how to increase the surface excess oxygen causes. Pretreatment redox catalyst can perovskite oxygen vacancy concentration is changed in a wide range . Presence of oxygen vacancies can induce a low amount of birth adsorption and desorption properties of adsorbed oxygen species , but also can improve the activity of lattice oxygen so that it can be improved catalytic performance . In this experimental condition , after H 2 pretreated at 300 ℃ reduction performance of the catalyst preferably 223 : oxygen vacancy concentration is 0.34, CO and NO conversion rate of 90 % of the temperatures were 231 ℃ and 213 ℃, HC conversion rate of 80% at a temperature of 400 ℃.

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