Supported copper–ceria catalysts for low temperature CO oxidation (original) (raw)
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Applied Catalysis A-general, 2005
CeO2 nanoparticles were prepared by thermal decomposition of cerous nitrate and then used as supports for CuO/CeO2 catalysts prepared via the impregnation method. The samples were characterized by HRTEM, XRD, H2-TPR, and XPS. The catalytic properties of the prepared catalysts for low-temperature CO oxidation were studied by using a microreactor–GC system. The results showed that the thermal decomposition temperature affected
CuO and CeO2 catalysts supported on Al2O3, ZrO2, and SiO2 in the oxidation of CO at low temperature
Applied Catalysis A: General, 2008
on the activity for CO oxidation of a series of CuO and CeO 2 monometallic and bimetallic catalysts was studied. The catalysts were prepared by coimpregnation of the support with the adequate amount of Cu and Ce nitrates to obtain a loading of 2% Cu and/or 8% Ce. It was found that the support has a strong influence on the activity of the different bimetallic catalysts. Interestingly, the SiO 2 supported catalyst shows the higher activity. The bimetallic supported catalysts follow the activity sequence CuO-CeO 2 /SiO 2 > CuO-CeO 2 /ZrO 2 > CuO-CeO 2 /Al 2 O 3 . In the absence of CeO 2 , the most active monometallic catalyst was the CuO/ZrO 2 system. The different degree of interaction between CuO and CeO 2 particles, induced by the support, can explain the activity results for the bimetallic catalysts.
Applied Catalysis A: General, 2005
CeO 2 nano-crystals were synthesized by a sol-gel process and then used as support for CuO/CeO 2 (sol-gel) catalysts prepared via impregnation method. For comparison, the commercial CeO 2 was also used as a support for CuO/CeO 2 (commercial) catalysts prepared via the same method. The samples were characterized by means of BET, XRD, UV-vis, TPR and XPS. The catalytic properties of the CuO/CeO 2 catalysts for low-temperature CO oxidation were studied by using a microreactor-GC system. The prepared spherical CeO 2 nano-crystals have much smaller particle size, better crystallinity and larger surface area than the commercial CeO 2 . XPS analysis indicated the presence of reduced copper species in the CuO/CeO 2 catalysts. TPR showed that there are different copper species in the catalysts. The influence of calcination time, temperature and CuO loadings on the catalytic activity of CuO/CeO 2 catalysts has been studied. The CuO/CeO 2 (sol-gel) catalysts exhibited higher catalytic activity than the CuO/CeO 2 (commercial) catalysts. Compared with CuO/CeO 2 catalysts prepared via other techniques, our catalysts exhibited similar or even better catalytic performance. # Fig. 4. XRD patterns of CuO/CeO 2 catalysts with various CuO loadings: (a) CuO/CeO 2 (sol-gel); (b) CuO/CeO 2 (commercial).
Selective CO oxidation over ceria supported CuO catalysts
Materials Chemistry and Physics, 2009
The effect of preparation method and pretreatment on the characteristic properties and selective CO oxidation activities of 50/50 CuO/CeO2, 25/25/50 CuO/Co3O4/CeO2 and 5/95 CuO/CeO2 catalysts was investigated. Catalysts were characterized by BET surface area measurement, N2 physisorption, SEM micrographs and X-ray diffraction. The selective oxidation reaction in H2 rich stream was carried out between the 110°C and 210°C temperatures. The
CuO/CeO2 catalysts: Redox features and catalytic behaviors
Applied Catalysis A: General, 2005
The reduction and oxidation features of nanostructured CuO/CeO 2 catalysts prepared by the deposition-precipitation method were extensively investigated by TPR, FT-IR and in situ XPS techniques. Both the chemical states of copper and the reduction degree of ceria could be well controlled during the reduction with hydrogen by adjusting the temperature. Noticeably, the fully reduced Cu 0 could be further oxidized into Cu + in hydrogen by increasing the reduction temperature through the interaction between Cu 0 and lattice oxygen of ceria immigrating to the surface. Structure-reactivity relationship was established between the structural features of CuO/CeO 2 formed during the pre-reduction with hydrogen and its catalytic activities for CO oxidation. It was observed that reduction with hydrogen at 473-573 K, which leads to the full presence of metallic copper in the catalyst, gives rise to higher CO conversion. These phenomena were interpreted in terms of the reduction degrees of ceria, the changes of surface morphology and the chemical states of copper species. The interface oxygen activation as well as its transfer from the interface to the adsorbed reactant was found to play decisive roles in determining the reaction rate of CO oxidation. #
Improved CO-PROX Performance of CuO/CeO2 Catalysts by Using Nanometric Ceria as Support
Catalysts
Despite of the huge number of papers about the catalytic preferential oxidation of CO (CO-PROX) for the purification of H2 streams, there is still a need for more effective catalysts in order to reduce the large required catalyst volume of CO-PROX unity. In this work, large surface area nanometric ceria was used as support for CuO/CeO2 catalysts with CuO load up to 10 wt % easily dispersed by wet impregnation. Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N2 physisorption, H2 temperature programmed reduction (TPR), and CO2 temperature programmed desorption (TPD) and tested under different reaction conditions (including under feed containing inhibiting species such as CO2 and H2O). Catalytic tests revealed that our samples show high activity and selectivity even under stringent reaction conditions; moreover, they result among the most active catalysts when compared to those reported in the scientific literature. The high activity can be related to the enhanced amount of highl...
Selective CO oxidation in excess of H 2 over high-surface area CuO/CeO 2 catalysts
Catalysis Today, 2008
The influence of the surface area, crystal size of the support and the Cu loading (3-9 wt.%) on the catalytic behavior of CuO/CeO 2 catalysts was investigated in the preferential CO oxidation (PROX) reaction. Two ceria samples were used: a high-surface area one (SCe) prepared by the templating technique and a low surface commercial one (ACe). Copper was incorporated to the calcined support by classical impregnation. Techniques were used to characterize the textural, structural and chemical properties of the catalysts (BET, XRD, HRTEM, and TPR). For catalysts supported on SCe these techniques evidenced highly dispersed copper species in strong interaction with nanosized CeO 2 crystals. The enhanced redox properties of the CuO-support interface sites at low temperature evidenced by TPR in CuSCe catalysts play a fundamental role in the catalytic behavior for the CO oxidation in presence of excess H 2 (PROX). CuSCe catalysts showed excellent catalytic activity compared to catalysts supported on the commercial CeO 2 . Total conversion of CO is obtained at 125 8C with 100% selectivity to CO 2 . In the presence of CO 2 and H 2 O the maximum CO conversion for temperatures higher than 125 8C was 95%. Selectivity also decreased being more pronounced when H 2 O was present. This negative effect was reversible since the original activity and selectivity were practically restored upon elimination of these components from the feed. Partially reduced Cu + species seem to be present in the catalysts according to CO adsorption followed by DRIFT. #
Effect of nature of ceria support in CuO/CeO 2 catalyst for PROX-CO reaction
Fuel, 2012
In order to understand the effect of CeO 2 on the preferential CO oxidation reaction (PROX-CO), the support cerium oxide was prepared by hydrothermal (CeO 2-HT) and precipitation (CeO 2-PP) methods. The catalyst supported on CeO 2-HT exhibited higher activity than CuO/CeO 2-PP. Characterization revealed that CuO was better dispersed on the CuO/CeO 2-HT surface favoring the PROX-CO reaction, compared to CuO/CeO 2-PP. Also, the nature of ceria was important for enhancing the metal-support interaction, which affects the catalytic activity. The CuO/CeO 2-HT catalyst was less sensitive to presence of CO 2 and H 2 O, remaining stable in a 24 h run.
Applied Catalysis B: Environmental, 2011
A Ce-Zr-Cu oxide system with a flower-like morphology was prepared by a slow co-precipitation method in the absence of any structure directing agent. Four portions of the oxide were thermally treated at four different temperatures (350 • C, 450 • C, 550 • C, 650 • C). The resulting materials samples were characterized by quantitative XRD, adsorption-desorption of N 2 at-196 • C, SEM and TEM microscopy, -H 2 -TPR, XPS and Operando-XANES. All samples were tested in the preferential CO oxidation (CO-PROX) in the 40-190 • C temperature range. Thermal treatments were found to induce slight structural changes without altering the starting morphology of the samples. The samples treated at higher temperature 550-650 • C showed a quite interesting CO-PROX activity and selectivity in a temperature range suitable for a practical use within the FEMFC technology. (M. Lenarda).
Carbon monoxide oxidation over CuO/CeO2 catalysts
Catalysis Today, 2004
CuO/CeO 2 catalysts prepared by co-precipitation, deposition-precipitation and impregnation methods were extensively investigated for CO oxidation reaction. It was shown that the catalytic behaviors of CuO/CeO 2 catalysts greatly depended on the preparation routes, which caused significant differences in the redox properties and the dispersion of copper species. The remarkable redox ability of CuO/CeO 2 at lower temperatures was found to play an essential role in CO oxidation reaction. The catalysts prepared by co-precipitation exhibited the highest catalytic activity in CO oxidation with CO total conversion at 85 • C. The structural characters as well as the redox features of CuO/CeO 2 catalysts were comparatively investigated by XRD, TPR, cyclic voltammetry and XPS measurements. The discrepancies in the dispersion of copper species and the degree of interaction between copper species and ceria determined the reversible redox properties, and consequently the catalytic performance.