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Publications (3)5.83 Total impact

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    ABSTRACT: The performance of Al2O3, ZrO2 and ZrO2 stabilized with SiO2 (ZrO2-s) supported palladium catalysts for the methane combustion was studied between 473 and 873 K. The nature of the surface species of palladium catalysts under reaction conditions were detected by FT-IR and microcalorimetry of CO adsorbed. The different behavior of palladium catalysts under reaction conditions is attributed to support effects associated to differences in thermal conductivity and oxygen mobility of supports. Prereduction of the catalysts enhances their activity. Under reaction conditions, the prereduced sample becomes partially oxidized by preferential adsorption/reaction of oxygen both on Pd ( 1 1 1) planes and on the sites that can multibondedly adsorb CO. The reconstruction of the metallic particles and the formation of PdOx (0<x 1) phase were directly observed by FT-IR and microcalorimetry of adsorbed CO. Combination of different characterization techniques with reaction results suggests that a mixed phase, Pd-0/PdOx, is the most active phase for methane combustion, and that a redox mechanism may occur on this phase. (C) 2000 Elsevier Science B.V. All rights reserved
    Applied Catalysis B Environmental 12/2000; 28. · 5.83 Impact Factor
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    ABSTRACT: The performance of Al2O3, ZrO2 and ZrO2 stabilized with SiO2 (ZrO2-s) supported palladium catalysts for the methane combustion was studied between 473 and 873K. The nature of the surface species of palladium catalysts under reaction conditions were detected by FT-IR and microcalorimetry of CO adsorbed. The different behavior of palladium catalysts under reaction conditions is attributed to support effects associated to differences in thermal conductivity and oxygen mobility of supports. Prereduction of the catalysts enhances their activity. Under reaction conditions, the prereduced sample becomes partially oxidized by preferential adsorption/reaction of oxygen both on Pd (111) planes and on the sites that can multibondedly adsorb CO. The reconstruction of the metallic particles and the formation of PdOx (0
    Applied Catalysis B-environmental - APPL CATAL B-ENVIRON. 01/2000; 28(3):223-233.
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    ABSTRACT: The adsorption of CO on Al2O3, ZrO2, ZrO2-SiO2, and ZrO2-La2O3 supported Pd catalysts was studied by adsorption microcalorimetry and infrared (TR) spectroscopy. Some interesting and new correlations between the results of microcalorimetry and IR spectroscopy have been found. The CO is adsorbed on palladium catalysts in three different modes: multibonded (3-fold), bridged (2-fold), both on Pd(lll) and (100) planes, and linear (1-fold) adsorbed species. The corresponding differential adsorption heats lie in the field of high (210-170 kJ/mol), medium (140-120 kJ/mol), and low (95-60 kJ/mol) values, respectively. The nature of the support, the reduction temperature, and the pretreatment conditions affect the surface structure of the Pd catalysts, resulting in variations in the site energy distribution, i.e., changes in the fraction of sites adsorbing CO with specific heats of adsorption. Moreover, the CeO2; promoter addition weakens the adsorption strength of CO on palladium. Based on the exposed results, a correctness factor, which considers the percentages of various CO adsorption states, must be introduced when one calculates the Pd dispersion using CO adsorption data
    Langmuir. 01/2000; 16(21).