Characterization and catalytic properties of CuO/CeO2/MgAl2O4 for preferential oxidation of CO in H2-rich streams
Catalysts of copper (1 wt.%) supported on a CeO2/MgAl2O4mixed support have been prepared by usingdifferent pH values (pH ∼ 4, 8 and 10) in the impregnating solution of copper with the aim of favoringdifferent situations of interaction between copper and the two support components. The catalysts have...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2016 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/414546 |
| Acceso en línea: | http://hdl.handle.net/10261/414546 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957990522&doi=10.1016%2Fj.apcatb.2016.02.011&partnerID=40&md5=1c89f352bcc7cb98ba72cc0329b1f09d |
| Access Level: | acceso abierto |
| Palabra clave: | CO-PROX DRIFTS EPR HREM Hydrogen Nanostructured CuO/CeO2/MgAl2O4 catalysts TPR XEDS XPS |
| Sumario: | Catalysts of copper (1 wt.%) supported on a CeO2/MgAl2O4mixed support have been prepared by usingdifferent pH values (pH ∼ 4, 8 and 10) in the impregnating solution of copper with the aim of favoringdifferent situations of interaction between copper and the two support components. The catalysts havebeen characterized in detail by XRD, SBETmeasurement, HREM and associated techniques, XPS, H2-TPRand EPR which allows establishing a model of structural characteristics of the catalysts. The characteriza-tion results have been correlated with analysis of the catalytic properties of the samples for preferentialoxidation of CO in a H2-rich stream (CO-PROX) complemented by operando-DRIFTS. Important struc-tural/chemical/catalytic differences as a function of the pH of the impregnating solution are revealed.These are explained on the basis of the characteristics of the interfaces formed between the differentcomponents present in each catalyst which basically determine the catalytic properties in each case.© 2016 Elsevier B.V. All rights reserved.1. IntroductionProduction of H2for polymer fuel cells (PEMFC) is usuallyaccomplished by a multi-step process that includes catalyticreforming of hydrocarbons or oxygenated hydrocarbons followedby water–gas shift (WGS) [1,2]. However, PEMFCs require hydrogenfeed that is mostly free from CO, as otherwise the Pt based anodecatalyst would be deactivated rapidly [2,3]. The high concentrationof CO is brought down to less than 0.5 mol.%, through a two-stagewater gas shift (WGS) reactor, in which CO is reacted with waterto produce hydrogen and carbon dioxide [4]. Since the CO level isstill much higher than a PEMFC anode can tolerate [4], it has tobe selectively oxidized to bring its concentration to very low level(typically below 100 ppm) in excess of H2(and with the presenceof H2O and CO2in the feed), which is a current challenge in hetero-geneous catalysis. Among different possibilities in this sense, thecatalytic preferential oxidation of CO (CO-PROX) is considered asmost simple and effective process to attain such goal [5–7].∗Corresponding author.E-mail address: amartinez@icp.csic.es (A. Martínez-Arias).The catalysts for CO-PROX reported in the scientific literaturecan be basically classified into three types: (i) noble metal cata-lysts based on Pt, Pd, Rh or Ir typically supported on Al2O3, SiO2orzeolites [6,7,8–17]; (ii) gold catalysts supported on different oxideslike MnOx, FeOx, TiO2, Al2O3, NiO, MgO and SnO2[6,7,18–21]; (iii)several kinds of base metal oxide catalysts, such as the oxides ofCu, Mn, Co, Ni and Fe, either alone or in combination with otheroxides [6,7,22–25]. Among the latter, catalysts combining copperand cerium oxides have demonstrated an important potential forthe process, being able to compete with less economically interest-ing noble metal catalysts; in particular, they generally show higherselectivity at full CO conversion than catalysts based on platinum-group metals and they appear more resistant to the presence ofCO2than catalysts based on gold [6,7,26]. The particular ability ofcopper-ceria catalysts for the CO-PROX process has been essentiallyattributed to the synergistic redox properties produced upon for-mation of copper oxide-ceria interfacial sites, which are consideredto constitute the active sites for the CO oxidation reaction [27–31].Further than the simple combination of copper and ceriumoxides, it is interesting from a practical point of view to explore theproperties of this type of catalysts when supported onto anotherfunctional material. Typically Al2O3, TiO2, MgAl2O4or SiO2areemployed as supports for oxidation catalysts due to their high ther- http://dx. |
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