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 °C, either in the presence or in the absence of excess O2 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 °C) even in the presence of excess O2, 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 °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.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights▸ The promotional effect of rare earth oxides on de-N2O over Pt/Al2O3 is demonstrated. ▸ The remarkable de-N2O performance is related with the formation of Pt nanoparticles. ▸ Pt sites located on the metal–support interface are responsible for the superior de-N2O activity.
Journal: Applied Catalysis B: Environmental - Volumes 123–124, 23 July 2012, Pages 405–413