Preferential CO oxidation on Pt–Cu/Al2O3 catalysts with low Pt loadings

This work demonstrates that a small loading of Pt (0.2–0.5 wt.%) selectively located at the top of the Cu/Al2O3 solid is enough to obtain active catalysts for the COPrOx reaction. The characterizations of the catalysts prepared in this work using different Pt:Cu ratios show that the phases formed st...

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Bibliographic Details
Published in:International journal of hydrogen energy 2014-03, Vol.39 (8), p.3719-3729
Main Authors: Gómez, Leticia E., Sollier, Brenda M., Mizrahi, Martín D., Ramallo López, José M., Miró, Eduardo E., Boix, Alicia V.
Format: Article
Language:English
Subjects:
Alternative fuels. Production and utilization
ALUMINUM OXIDE
Applied sciences
Catalysis
CATALYSTS
Copper
COPPER OXIDE
COPrOx
Distortion
Energy
Exact sciences and technology
EXAFS-XANES
Fuels
Hydrogen
Noble metals
PHASES
Platinum
Pt–Cu bimetallic
XPS
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Summary:This work demonstrates that a small loading of Pt (0.2–0.5 wt.%) selectively located at the top of the Cu/Al2O3 solid is enough to obtain active catalysts for the COPrOx reaction. The characterizations of the catalysts prepared in this work using different Pt:Cu ratios show that the phases formed strongly depend on the Cu and Pt loadings. For the samples with 4 wt.% of Cu, the formation of defective CuAl2O4-like species is predominant, with Cu2+ occupying distorted sites in the alumina surface. For the samples with 8 wt.% of Cu, CuO and metallic Cu in the form of small crystals are observed besides Cu2+. For both 0.2 and 0.5 wt.% of Pt, some proportion of Cu–Pt alloy is found which increased with the Cu content. Metallic Pt particles are only observed by EXAFS for the samples with a higher loading of the noble metal. The higher CO conversions at low temperatures were obtained for the Pt0.5Cu8/Al2O3 sample, probably due to the simultaneous formation of small Pt crystals in close contact with CuO. The XPS results show that a strong surface enrichment in Pt takes place in all the samples. Thus, a small loading of the noble metal is enough to obtain effective catalysts. The surface Pt enrichment observed is most probably due to the impregnation of the Pt salt onto the Cu/Al2O3 solid, with a relatively low calcination temperature (300 °C) that prevents the formation of bulky CuAl2O4 spinel crystals. •Catalysts Cu/Al2O3 with a small loading of Pt on top of them are active for COPrOx.•Cu–Pt alloy and Pt(0) particles are found on the catalyst surface.•The surface Pt enrichment is probably due to the preparation strategy.
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2013.12.146