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|Type:||Artigo de periódico|
|Title:||Catalytic Partial Oxidation And Steam Reforming Of Methane On La 2o 3-al 2o 3 Supported Pt Catalysts As Observed By X-ray Absorption Spectroscopy|
|Abstract:||Structural transformations of Pt supported on Al 2O 3 or La 2O 3-Al 2O 3 were studied by X-ray absorption near edge structure (XANES) at the Pt L 3 edge during heating and cooling under partial oxidation of methane (POM) conditions, and by extended X-ray absorption fine structure (EXAFS) under steam reforming of methane (SRM) conditions. Ignition of the POM reaction occurred simultaneously with the reduction of PtO 2 to metallic Pt, indicating that the ignition occurs on metallic Pt. When the temperature of the POM reaction was decreased, carbon accumulated on the metallic Pt surface, and the activation of CH 4 was suppressed at about 370 °C. Nevertheless, the oxidation of carbon remaining on the metallic Pt surface continued until a temperature of around 270 °C was reached, when oxidation of Pt occurred and the oxidation reactions were extinguished. The EXAFS data obtained during SRM and under H 2 suggest that complex alterations in the structure of Pt particles occur with changes of temperature and reactant composition. The SRM activity of Pt catalysts depends on both the access of CH 4 to active Pt sites, and the changes in the structure of Pt particles under reaction conditions. For both reactions, Pt supported on La 2O 3-Al 2O 3 was more stable than Pt supported on Al 2O 3, indicating a higher stability of Al 2O 3 modified with La 2O 3. © 2012 Elsevier B.V. All rights reserved.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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