In situ EXAFS and FTIR studies of the promotion behavior of Pt-Nb2O5/Al2O3 catalysts during the preferential oxidation of CO

S. Guerrero; J. T. Miller; A. J. Kropf; E. E. Wolf

doi:10.1016/j.jcat.2008.12.008

In situ EXAFS and FTIR studies of the promotion behavior of Pt-Nb₂O₅/Al₂O₃ catalysts during the preferential oxidation of CO

S. Guerrero, J. T. Miller, A. J. Kropf, E. E. Wolf^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

The promotional effect of Nb to Pt/Al₂O₃ supported catalysts during the preferential oxidation of CO (PROX) was studied using various spectroscopic techniques. Addition of small amounts of Nb (<5%) stabilizes 40% of the loaded platinum as Pt²⁺, which remains oxidized even after reduction treatments. This Nb-promoted catalyst is very active and selective for the PROX reaction. On Pt/Nb₂O₅ and at high Nb loading for the Pt/Nb/Al₂O₃ catalysts, the selectivity to CO₂ decreases and the selectivity for H₂ oxidation increases opposite to the selectivity observed at low Nb loadings. The increase CO₂ selectivity due to Nb promotion is ascribed to the inhibition of CO at low temperature which decreases hydrogen oxidation. Operando FTIR results indicate the presence of adsorbed CO as well as carbonates, bicarbonates and formates during the PROX reaction. An IR band at 968 cm^-1 indicates the presence of Nb{double bond, long}O moieties at low Nb loadings. At higher Nb loadings, IR suggests the formation of three-dimensional Nb₂O₅ aggregates. The surface of the Nb containing catalysts is complex containing reduced and oxidized Pt which is modified by NbO_x species either surrounding the Pt crystallites or decorating them.

Original language	English
Pages (from-to)	102-110
Number of pages	9
Journal	Journal of Catalysis
Volume	262
Issue number	1
DOIs	https://doi.org/10.1016/j.jcat.2008.12.008
State	Published - 15 Feb 2009
Externally published	Yes

Bibliographical note

Funding Information:
We gratefully acknowledge partial support of this work by a grant from Companhia Brasileira de Metalurgia e Mineração, CBMM; a Bayer Postdoctoral Fellowship in Environmental Chemistry through the Center for Environmental Science and Technology at the University of Notre Dame, and NSF Grant CTS 0138070. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Basic Energy Sciences, Office of Science (DOE-BES-SC), under Contract No W-31-109-Eng-38. The MRCAT is funded by the member institutions and DOE-BES-SC under contracts DE-FG02-94ER45525 and DE-FG02-96ER45589.

Keywords

Nb promoter
PROX reaction
Pt supported catalyst

Access to Document

10.1016/j.jcat.2008.12.008

Cite this

@article{8184930b66424a92b58728700f0789df,

title = "In situ EXAFS and FTIR studies of the promotion behavior of Pt-Nb2O5/Al2O3 catalysts during the preferential oxidation of CO",

abstract = "The promotional effect of Nb to Pt/Al2O3 supported catalysts during the preferential oxidation of CO (PROX) was studied using various spectroscopic techniques. Addition of small amounts of Nb (<5%) stabilizes 40% of the loaded platinum as Pt2+, which remains oxidized even after reduction treatments. This Nb-promoted catalyst is very active and selective for the PROX reaction. On Pt/Nb2O5 and at high Nb loading for the Pt/Nb/Al2O3 catalysts, the selectivity to CO2 decreases and the selectivity for H2 oxidation increases opposite to the selectivity observed at low Nb loadings. The increase CO2 selectivity due to Nb promotion is ascribed to the inhibition of CO at low temperature which decreases hydrogen oxidation. Operando FTIR results indicate the presence of adsorbed CO as well as carbonates, bicarbonates and formates during the PROX reaction. An IR band at 968 cm-1 indicates the presence of Nb{double bond, long}O moieties at low Nb loadings. At higher Nb loadings, IR suggests the formation of three-dimensional Nb2O5 aggregates. The surface of the Nb containing catalysts is complex containing reduced and oxidized Pt which is modified by NbOx species either surrounding the Pt crystallites or decorating them.",

keywords = "Nb promoter, PROX reaction, Pt supported catalyst",

author = "S. Guerrero and Miller, {J. T.} and Kropf, {A. J.} and Wolf, {E. E.}",

note = "Funding Information: We gratefully acknowledge partial support of this work by a grant from Companhia Brasileira de Metalurgia e Minera{\c c}{\~a}o, CBMM; a Bayer Postdoctoral Fellowship in Environmental Chemistry through the Center for Environmental Science and Technology at the University of Notre Dame, and NSF Grant CTS 0138070. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Basic Energy Sciences, Office of Science (DOE-BES-SC), under Contract No W-31-109-Eng-38. The MRCAT is funded by the member institutions and DOE-BES-SC under contracts DE-FG02-94ER45525 and DE-FG02-96ER45589.",

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T1 - In situ EXAFS and FTIR studies of the promotion behavior of Pt-Nb2O5/Al2O3 catalysts during the preferential oxidation of CO

AU - Guerrero, S.

AU - Miller, J. T.

AU - Kropf, A. J.

AU - Wolf, E. E.

N1 - Funding Information: We gratefully acknowledge partial support of this work by a grant from Companhia Brasileira de Metalurgia e Mineração, CBMM; a Bayer Postdoctoral Fellowship in Environmental Chemistry through the Center for Environmental Science and Technology at the University of Notre Dame, and NSF Grant CTS 0138070. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Basic Energy Sciences, Office of Science (DOE-BES-SC), under Contract No W-31-109-Eng-38. The MRCAT is funded by the member institutions and DOE-BES-SC under contracts DE-FG02-94ER45525 and DE-FG02-96ER45589.

PY - 2009/2/15

Y1 - 2009/2/15

N2 - The promotional effect of Nb to Pt/Al2O3 supported catalysts during the preferential oxidation of CO (PROX) was studied using various spectroscopic techniques. Addition of small amounts of Nb (<5%) stabilizes 40% of the loaded platinum as Pt2+, which remains oxidized even after reduction treatments. This Nb-promoted catalyst is very active and selective for the PROX reaction. On Pt/Nb2O5 and at high Nb loading for the Pt/Nb/Al2O3 catalysts, the selectivity to CO2 decreases and the selectivity for H2 oxidation increases opposite to the selectivity observed at low Nb loadings. The increase CO2 selectivity due to Nb promotion is ascribed to the inhibition of CO at low temperature which decreases hydrogen oxidation. Operando FTIR results indicate the presence of adsorbed CO as well as carbonates, bicarbonates and formates during the PROX reaction. An IR band at 968 cm-1 indicates the presence of Nb{double bond, long}O moieties at low Nb loadings. At higher Nb loadings, IR suggests the formation of three-dimensional Nb2O5 aggregates. The surface of the Nb containing catalysts is complex containing reduced and oxidized Pt which is modified by NbOx species either surrounding the Pt crystallites or decorating them.

AB - The promotional effect of Nb to Pt/Al2O3 supported catalysts during the preferential oxidation of CO (PROX) was studied using various spectroscopic techniques. Addition of small amounts of Nb (<5%) stabilizes 40% of the loaded platinum as Pt2+, which remains oxidized even after reduction treatments. This Nb-promoted catalyst is very active and selective for the PROX reaction. On Pt/Nb2O5 and at high Nb loading for the Pt/Nb/Al2O3 catalysts, the selectivity to CO2 decreases and the selectivity for H2 oxidation increases opposite to the selectivity observed at low Nb loadings. The increase CO2 selectivity due to Nb promotion is ascribed to the inhibition of CO at low temperature which decreases hydrogen oxidation. Operando FTIR results indicate the presence of adsorbed CO as well as carbonates, bicarbonates and formates during the PROX reaction. An IR band at 968 cm-1 indicates the presence of Nb{double bond, long}O moieties at low Nb loadings. At higher Nb loadings, IR suggests the formation of three-dimensional Nb2O5 aggregates. The surface of the Nb containing catalysts is complex containing reduced and oxidized Pt which is modified by NbOx species either surrounding the Pt crystallites or decorating them.

KW - Nb promoter

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KW - Pt supported catalyst

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