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The effect of precursors salts on surface state of Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts Anais da ABC (AABC)
Guimarães,André L.; Dieguez,Lídia C.; Schmal,Martin.
The influence of the precursors on the promoting effect of ceria on Pd/Al2O3 catalyst, when ceria is coated over alumina was studied. The reaction of propane oxidation proceeded under different feed conditions and the surface active sites were characterized by X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance spectroscopy (DRS). XPS and DRS results show that PdO/Pd0 interface are the active sites independent of the precursor, while the catalysts containing CeO2 showed formation of palladium species in the highest oxidation state, probably PdO2 (338 eV) after the oxidation of propane. Besides, the O/Al and O/Ce ratios evidenced the increase of oxygen storage in the presence of CeO2. In addition, the precursor acetylacetonate favors the...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Palladium; Cerium oxide; Precursors; Characterization.
Ano: 2004 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652004000400014
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The promoting effect of cesium on structure and morphology of silver catalysts Anais da ABC (AABC)
Carvalho,Marta C. N. A.; Perez,Carlos A.; Simão,Renata A.; Passos,Fabio B.; Schmal,Martin.
Silver supported catalysts on alpha-alumina were prepared and characterized by Brunauer-Emmet-Teller equations, scanning electronic microscopy, X-ray diffraction and atomic force microscopy techniques. Results show that these are powerful techniques for the determination of texture, morphology and surface properties. It has been shown that the addition of Cs in the Ag/Al2O3 catalyst increased the dispersion of silver with the formation of small silver particles over a thin silver film already formed over the alumina support. It is important to stress that atomic force microscopy measurements are significant to observe the film and the dispersion of Ag and, on the contrary, X-ray photoelectronic spectroscopy did not, however, it allows to the conclusion...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Silver; Cesium; Catalyst; AFM; XPS.
Ano: 2004 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652004000100003
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Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science Anais da ABC (AABC)
Schmal,Martin; Freund,Hans-Joachim.
The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993). The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Catalysis; Model catalysts; Cobalt; Palladium; Characterization; Niobia.
Ano: 2009 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652009000200016
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