Selective oxidation of CO in H2-rich stream over Au/CeO2 and Cu/CeO2 catalysts: An insight on the effect of preparation method and catalyst pretreatment

Scirè, Salvatore; Crisafulli, C.; Riccobene, Paolo Maria; Patané, Giacomo; Pistone, Alessandro

doi:10.1016/j.apcata.2011.12.025

Cited by 56 publications

(36 citation statements)

References 68 publications

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“…In order to obtain a good yield, it is then necessary to activate CO and not H 2 . It is well known that cerium oxide has good catalytic properties for oxidation reactions, since it has mobile/reducible oxygens [6,12,13,43,68]. The mobility of such oxygens can be increased by the presence of metals on the surface, which introduce crystalline defects that increase the mobility of these oxygens and increasing the oxidative power of the substrate [12,43,67].…”

Section: Discussionmentioning

confidence: 99%

“…In the case of the Ru/CeO 2 -CuO catalyst, CO conversion shifted to a higher temperature, probably due to the fact that Cu catalysts require higher temperatures to promote the CO oxidation [12,13,25]. However, it cannot be fully ruled out that the low activity of the Ru/CeO 2 -CuO catalyst can be related to an unsuitable pretreatment of the CuO-CeO 2 system, for which calcination at 450 • C (adopted here for all samples) could not be ideal for the formation of the active Cu + sites [19,20].…”

Section: Catalytic Activitymentioning

confidence: 99%

“…Temperature Programmed Reduction (H 2 -TPR) Figure 3 shows the H 2 -temperature programmed reduction profiles of the analyzed samples between 50 • C and 500 • C. On the bare cerium oxide support, the H 2 consumption starts at around 350 • C, due to the partial reduction of the CeO 2 surface oxygen [12,13]. The reduction of bulk oxygen was reported to take place at temperatures higher than 700 • C [32] and, therefore, is not visible in the TPR curve of Figure 3.…”

Section: Catalysts Characterizationmentioning

confidence: 99%

“…Recently, the use of a reducible/active support, such as cerium oxide or iron oxide, resulted in remarkably low-temperature CO-PROX activities [12,17]. The peculiar red-ox properties of CeO 2 involving the facile exchange between Ce 3+ and Ce 4+ states and the high mobility of O 2-ions in the lattice, are the key factors to explain the high relevance of this oxide as a metal support in the PROX reaction [6,12,13,18].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the catalyst of this process must be highly selective towards the first reaction. Noble-metal catalysts, such as Pd [8], Rh [9], Ru [10,11], Au [12][13][14] and Pt [15,16], have revealed good CO-PROX performance. The selection of the proper support has been also found crucial in addressing the catalytic activity.…”

Section: Introductionmentioning

confidence: 99%

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Ru–Pd Bimetallic Catalysts Supported on CeO2-MnOX Oxides as Efficient Systems for H2 Purification through CO Preferential Oxidation

et al. 2018

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Abstract:The catalytic performances of Ru/ceria-based catalysts in the CO preferential oxidation (CO-PROX) reaction are discussed here. Specifically, the effect of the addition of different oxides to Ru/CeO 2 has been assessed. The Ru/CeO 2 -MnO x system showed the best performance in the 80-120 • C temperature range, advantageous for polymer-electrolyte membrane fuel cell (PEMFC) applications. Furthermore, the influence of the addition of different metals to this mixed oxide system has been evaluated. The bimetallic Ru-Pd/CeO 2 -MnO x catalyst exhibited the highest yield to CO 2 (75%) at 120 • C whereas the monometallic Ru/CeO 2 -MnO x sample was that one with the highest CO 2 yield (60%) at 100 • C. The characterization data (H 2 -temperature programmed reduction (H 2 -TPR), X-ray diffraction (XRD), N 2 adsorption-desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS)) pointed out that the co-presence of manganese oxide and ruthenium enhances the mobility/reactivity of surface ceria oxygens accounting for the good CO-PROX performance of this system. Reducible oxides as CeO 2 and MnO x , in fact, play two important functions, namely weakening the CO adsorption on the metal active sites and providing additional sites for adsorption/activation of O 2 , thus changing the mechanism from competitive Langmuir-Hinshelwood into non-competitive one-step dual site Langmuir-Hinshelwood/Mars-van Krevelen. As confirmed by H 2 -TPR and XPS measurements, these features are boosted by the simultaneous presence of ruthenium and palladium. The strong reciprocal interaction of these metals between them and with the CeO 2 -MnO x support was assumed to be responsible of the promoted reducibility/reactivity of CeO 2 oxygens, thus resulting in the best CO-PROX efficiency at low temperature of the Ru-Pd/CeO 2 -MnO x catalyst. The higher selectivity to CO 2 found on the Ru-Pd system, which reduces the undesired H 2 consumption, represents a promising result of this research, being one of the key aims of the design of CO-PROX catalysts.

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