Catalytic combustion of volatile organic compounds (VOC) and preferential oxidation of CO (PROX) were investigated over IB metal/ceria catalysts prepared by deposition-precipitation (DP) or coprecipitation (CP). The activity towards the deep oxidation of VOC was in the order: Au/CeO(2) >= Ag/CeO(2) > Cu/CeO(2) >> CeO(2). The same trend was also found in the PROX reaction in terms of total conversion of O(2), which includes O(2) consumed both for CO and H(2) oxidation. A different behaviour was observed in the CO conversion to CO(2). that is the desired PROX reaction. For this reaction, in fact, Au and Cu catalysts gave high CO conversions, Au/CeO(2) at low temperature (maximum of 84.3% for AuDP at 70 degrees C) and Cu/CeO(2) at higher temperature (maximum of 96.8% for CuCP at 150 degrees C), whereas Ag catalysts always exhibited very low CO conversions (maximum of 16.7% for AgCP at 80 degrees C). Both for PROX and VOC combustion the Au sample prepared by DP was more active than the CP one, whereas a reverse behaviour was found on Ag and Cu catalysts. On the basis of characterization data (XRD, H(2)-TPR, surface area measurements. N(2)-D(2) isotopic exchange, N(2)O and H(2)-O(2) chemisorption) it was proposed that a higher atomic radius of the IB metal and the presence of smaller crystallites of both IB metal and ceria result in a larger enhancement of mobility/reactivity of surface ceria oxygens, involved in both investigated reactions through a Mars-van Krevelen mechanism. The very low PROX activity of Ag/CeO(2) samples was related to the low capacity of silver to activate the CO molecule. (C) 2010 Elsevier B.V. All rights reserved.
|Titolo:||Ceria supported group IB metal catalysts for the combustion of volatile organic compounds and the preferential oxidation of CO|
|Data di pubblicazione:||2010|
|Appare nelle tipologie:||1.1 Articolo in rivista|