Identifying the adsorbed active intermediates on Pt surface and promotion of activity through the redox CeO^sub 2^ in preferential oxidation of CO in H^sub 2

A series of non- and modified with niobia and ceria alumina-supported Pt catalysts with different Pt content (0.3-2 wt%) were prepared by wetness impregnation method and characterized by N2 adsorption-desorption isotherms, XRD, TPR, DRIFT, in situ EXAFS and ΔXANES. The effect of the content of Pt an...

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Bibliographic Details
Published in:Applied catalysis. A, General General, 2017-11, Vol.548, p.164
Main Authors: Paz, DS, Damyanova, S, Borges, LR, Santos, JBO, Bueno, JMC
Format: Article
Language:English
Subjects:
Adsorption
Aluminum oxide
Catalysis
Catalysts
Cerium oxides
Cobalt
Desorption
Electron density
Electronic structure
Moisture content
Oxidation
Platinum
Promotion
Reagents
Selectivity
Strong interactions (field theory)
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Summary:A series of non- and modified with niobia and ceria alumina-supported Pt catalysts with different Pt content (0.3-2 wt%) were prepared by wetness impregnation method and characterized by N2 adsorption-desorption isotherms, XRD, TPR, DRIFT, in situ EXAFS and ΔXANES. The effect of the content of Pt and promoter on the change of catalyst electronic structure and behaviors in the reaction of preferential oxidation of CO in the presence of H2 was studied. A strong interaction of Pt with CO and O2 in atmospheres of H2/CO and H2/CO/O2 mixtures was detected by ΔXANES. Different steps of activation of reagents molecules were observed. The increase of activity with increasing the Pt content was related to the presence of Pt nanoparticles with high electron density. While, the highest metal dispersion of the low metal-loaded Pt catalyst was responsible for its high CO oxidation selectivity. Addition of ceria to Pt catalysts caused significantly increase of activity and CO oxidation selectivity at lower reaction temperatures. Niobia addition did not improve the catalysts behaviors. The promotion effect of ceria was related to the oxygen mobility at Pt-O-Ce interface. The ceria-promoted Pt catalysts with the highest ceria loading of 12 wt% exhibited the highest activity and CO oxidation selectivity, but at higher reaction temperatures of about 110-130 °C it was begin slowly to decrease. This was attributed to going on the reverse of WGS reaction and high O2 consumption to H2 oxidation during the PROX-CO reaction on ceria alumina-supported Pt catalysts at high temperatures.
ISSN:0926-860X
1873-3875