Support mediated promotional effects of rare earth oxides (CeO2 and La2O3) on N2O decomposition and N2O reduction by CO or C3H6 over Pt/Al2O3 structured catalysts

The N2O decomposition and reduction by CO or C3H6 over rare earth oxides (REOs)-modified Pt/Al2O3 structured catalysts, i.e.. coated on ceramic honeycomb monoliths, were comparatively investigated in a wide temperature interval of 100-600 degrees C, either in the presence or in the absence of excess O-2 and H2O. It was shown that the de-N2O efficiency can be remarkably enhanced via modification of Al2O3 support with rare earth oxides (REOs). In specific, complete conversion of N2O can be attained over REOs-modified catalysts at a relatively low temperature (ca. 480 degrees C) even in the presence of excess O-2, which in general depresses de-N2O efficiency, in opposite to the unmodified Pt/Al2O3 catalyst, over which. 20% N2O conversion is never exceeded for temperatures up to 600 degrees C. In terms of turnover frequency (TOF), optimally modified (by REOs) Pt-Al2O3 catalyst exhibits one order of magnitude higher activity compared to that of the unpromoted Pt/Al2O3 sample. Under reducing conditions the N2O conversion is strongly enhanced by C3H6 and especially by CO, whereas marginal inhibition is induced by reducing agents under excess oxygen conditions. Water was found to induce a detrimental influence on N2O decomposition, with its effect however, to be partially reversible. An in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study, using CO as a probe molecule, was performed over both unmodified and REOs-modified Pt/Al2O3 catalysts to correlate their surface characteristics with their de-N2O efficacy. The results revealed that the superior catalytic performance of promoted samples could be mainly attributed to the increase of Pt dispersion as well as to the development of Pt sites with exceptional electron density, located on the metal-support interfacial area. (C) 2012 Elsevier B.V. All rights reserved.