Three different catalysts, namely Pt/γ-Al2O3, Au/α-Fe2O3 and CuO–CeO2 were prepared (by wet impre... more Three different catalysts, namely Pt/γ-Al2O3, Au/α-Fe2O3 and CuO–CeO2 were prepared (by wet impregnation, coprecipitation and a sol–gel method, respectively) and their catalytic performance for the selective oxidation of carbon monoxide in the presence of excess hydrogen was evaluated and compared. The effects of the presence of CO2 and H2O in the reactant feed on the activity and selectivity of these catalysts, as well as their stability under realistic reaction conditions were also investigated.Regardless of whether CO2 or both CO2 and H2O are present in the reactant feed, the Au/α-Fe2O3 catalyst is superior to the other two for the selective CO oxidation at relatively low reaction temperatures (<80–120°C, depending on contact time and feed composition employed), while at higher reaction temperatures, best results are obtained with the CuO–CeO2 catalyst, which proved to be more active and remarkably more selective than the Pt/γ-Al2O3 catalyst. The Au/α-Fe2O3 catalyst was the most sensitive, while the Pt/γ-Al2O3 the most resistant towards deactivation caused by the presence of CO2 and H2O in the feed. Finally, while the Au/α-Fe2O3 catalyst lost a considerable portion of its activity during the first 80h under reaction conditions, the CuO–CeO2 and Pt/γ-Al2O3 catalysts exhibited a stable catalytic performance, at least during the time period tested in this work (7–8 days).
A series of mixed oxide CuO–CeO2 catalysts were prepared by coprecipitation and tested for the se... more A series of mixed oxide CuO–CeO2 catalysts were prepared by coprecipitation and tested for the selective oxidation of carbon monoxide in the presence of excess hydrogen. These catalysts were found to be very active and exceptionally selective for this reaction and exhibited a good resistance towards CO2 and H2O. The catalytic performance of these non-noble metal containing catalysts is compared with that of other selective CO oxidation catalysts reported in literature.
In this work we report on the influence of the preparation method on the physicochemical and cata... more In this work we report on the influence of the preparation method on the physicochemical and catalytic properties of CuO–CeO2 catalysts for the selective CO oxidation in simulated reformate gas. Four CuO–CeO2 samples were prepared using the co-precipitation, the citrate-hydrothermal, the urea-nitrates combustion, and the impregnation methods, and characterized by N2 adsorption–desorption, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction by H2 (TPR-H2).The combustion-prepared sample exhibited the best catalytic performance, closely followed by that prepared with the citrate-hydrothermal method. The co-precipitated sample was less active followed by the impregnated one. The activity of all samples decreases in the presence of CO2 and, to a higher degree, in the simultaneous presence of both CO2 and H2O in the feed. The resistance to this deactivation was higher in the case of the sample prepared by the urea-nitrates combustion method, which remained the most active and selective, closely followed by the specimen prepared by the citrate-hydrothermal method. The superior catalytic performance of the samples prepared by the urea-nitrates combustion and the citrate-hydrothermal methods is attributed to the existence of well dispersed, strongly interacting with the ceria surface, copper oxide species.
ABSTRACT The combustion method was employed for the in situ synthesis of nanocrystalline Cu-Ce-O ... more ABSTRACT The combustion method was employed for the in situ synthesis of nanocrystalline Cu-Ce-O and Cu-Mn-O catalyst layers on Al metal foam, without the need of binder or additional calcination steps. Copper-manganese spinel oxides have been proposed as a catalytic system for hydrogen production via methanol steam reforming, while CuO-CeO2 catalysts have been successfully examined for CO removal from reformed fuels via selective oxidation. In this work, the performance of these catalysts supported on Al metal foam has been investigated in the reactions of methanol reforming and selective CO oxidation. The Cu-Ce-O foam catalyst exhibited similar catalytic performance to the one of the powder catalyst in the selective oxidation of CO. The performance of the Cu-Mn-O foam catalyst in the steam reforming of methanol was inferior to the one of the powder catalyst at intermediate conversion levels, but almost complete conversion of methanol was obtained at the same temperature with both foam and powder catalysts.
ABSTRACT This chapter examines surface acidity and catalytic activity of cobalt (Co) and magnesiu... more ABSTRACT This chapter examines surface acidity and catalytic activity of cobalt (Co) and magnesium (Mg) incorporated and impregnated in AlPO4-34 with ammonia adsorption, temperature-programmed desorption (TPD) and with the reaction of carbon monoxide (CO) oxidation. Incorporation of Co in the framework of A1PO4-34 leads to the enhancement of surface acidity and to the formation of strong acid sites while in MnAPO-34 this effect is less pronounced. Samples with extraframework Co and Mg possess weak acid centres. CoAPO-34 is one to two orders of magnitude more active than Co/A1PO4-34 while Me/A1PO4-34 and MnAPO-34 are almost inactive in the reaction of CO oxidation.
Three different catalysts, namely Pt/γ-Al2O3, Au/α-Fe2O3 and CuO–CeO2 were prepared (by wet impre... more Three different catalysts, namely Pt/γ-Al2O3, Au/α-Fe2O3 and CuO–CeO2 were prepared (by wet impregnation, coprecipitation and a sol–gel method, respectively) and their catalytic performance for the selective oxidation of carbon monoxide in the presence of excess hydrogen was evaluated and compared. The effects of the presence of CO2 and H2O in the reactant feed on the activity and selectivity of these catalysts, as well as their stability under realistic reaction conditions were also investigated.Regardless of whether CO2 or both CO2 and H2O are present in the reactant feed, the Au/α-Fe2O3 catalyst is superior to the other two for the selective CO oxidation at relatively low reaction temperatures (<80–120°C, depending on contact time and feed composition employed), while at higher reaction temperatures, best results are obtained with the CuO–CeO2 catalyst, which proved to be more active and remarkably more selective than the Pt/γ-Al2O3 catalyst. The Au/α-Fe2O3 catalyst was the most sensitive, while the Pt/γ-Al2O3 the most resistant towards deactivation caused by the presence of CO2 and H2O in the feed. Finally, while the Au/α-Fe2O3 catalyst lost a considerable portion of its activity during the first 80h under reaction conditions, the CuO–CeO2 and Pt/γ-Al2O3 catalysts exhibited a stable catalytic performance, at least during the time period tested in this work (7–8 days).
A series of mixed oxide CuO–CeO2 catalysts were prepared by coprecipitation and tested for the se... more A series of mixed oxide CuO–CeO2 catalysts were prepared by coprecipitation and tested for the selective oxidation of carbon monoxide in the presence of excess hydrogen. These catalysts were found to be very active and exceptionally selective for this reaction and exhibited a good resistance towards CO2 and H2O. The catalytic performance of these non-noble metal containing catalysts is compared with that of other selective CO oxidation catalysts reported in literature.
In this work we report on the influence of the preparation method on the physicochemical and cata... more In this work we report on the influence of the preparation method on the physicochemical and catalytic properties of CuO–CeO2 catalysts for the selective CO oxidation in simulated reformate gas. Four CuO–CeO2 samples were prepared using the co-precipitation, the citrate-hydrothermal, the urea-nitrates combustion, and the impregnation methods, and characterized by N2 adsorption–desorption, X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction by H2 (TPR-H2).The combustion-prepared sample exhibited the best catalytic performance, closely followed by that prepared with the citrate-hydrothermal method. The co-precipitated sample was less active followed by the impregnated one. The activity of all samples decreases in the presence of CO2 and, to a higher degree, in the simultaneous presence of both CO2 and H2O in the feed. The resistance to this deactivation was higher in the case of the sample prepared by the urea-nitrates combustion method, which remained the most active and selective, closely followed by the specimen prepared by the citrate-hydrothermal method. The superior catalytic performance of the samples prepared by the urea-nitrates combustion and the citrate-hydrothermal methods is attributed to the existence of well dispersed, strongly interacting with the ceria surface, copper oxide species.
ABSTRACT The combustion method was employed for the in situ synthesis of nanocrystalline Cu-Ce-O ... more ABSTRACT The combustion method was employed for the in situ synthesis of nanocrystalline Cu-Ce-O and Cu-Mn-O catalyst layers on Al metal foam, without the need of binder or additional calcination steps. Copper-manganese spinel oxides have been proposed as a catalytic system for hydrogen production via methanol steam reforming, while CuO-CeO2 catalysts have been successfully examined for CO removal from reformed fuels via selective oxidation. In this work, the performance of these catalysts supported on Al metal foam has been investigated in the reactions of methanol reforming and selective CO oxidation. The Cu-Ce-O foam catalyst exhibited similar catalytic performance to the one of the powder catalyst in the selective oxidation of CO. The performance of the Cu-Mn-O foam catalyst in the steam reforming of methanol was inferior to the one of the powder catalyst at intermediate conversion levels, but almost complete conversion of methanol was obtained at the same temperature with both foam and powder catalysts.
ABSTRACT This chapter examines surface acidity and catalytic activity of cobalt (Co) and magnesiu... more ABSTRACT This chapter examines surface acidity and catalytic activity of cobalt (Co) and magnesium (Mg) incorporated and impregnated in AlPO4-34 with ammonia adsorption, temperature-programmed desorption (TPD) and with the reaction of carbon monoxide (CO) oxidation. Incorporation of Co in the framework of A1PO4-34 leads to the enhancement of surface acidity and to the formation of strong acid sites while in MnAPO-34 this effect is less pronounced. Samples with extraframework Co and Mg possess weak acid centres. CoAPO-34 is one to two orders of magnitude more active than Co/A1PO4-34 while Me/A1PO4-34 and MnAPO-34 are almost inactive in the reaction of CO oxidation.
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Papers by George Avgouropoulos