Publisher's statementThis is the author's version of a work that was accepted for publication in Applied Catalysis B: Environmental. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Applied Catalysis B: Environmental, 108-109 (1) Ce (x) Zr (1-x) O 2 catalysts with various Ce / Zr contents were studied using Raman spectroscopy under different gaseous atmospheres, at different temperatures and in the presence of a model soot.Catalysts with high concentrations of Zr fluoresced at elevated temperatures making analysis of their spectra impossible. This effect became even more pronounced at higher temperatures. CeO 2 and solid solutions with relatively low concentrations of Zr showed a red shift and a decrease in intensity of the characteristic F 2g peak at high temperatures under different atmospheres. The magnitude of the latter effect was higher under reducing atmospheres. These changes are reversible upon cooling, showing that they relate to a lattice expansion effect rather than any major chemical change to the material. In the presence of the model soot the Raman spectra of all materials was much decreased due to the absorption of the incident and scattered radiation by the soot particles. The presence of soot does not change the relative intensities or positions of the peaks in the spectra of the solid solutions. Evidence is shown for the production of a Ce 3+ -CO species following interaction between the soot and the surface at high temperature in an inert atmosphere.
A series of rare earth (RE) (La, Nd, Pr) ceria zirconia materials were analysed for their soot combustion activity in air and in NO/O 2 . The materials were characterised using DRIFT spectroscopy. In general the presence of the RE dopant increases the activity of undoped Ce x Zr 1-x O 2 . The La and Pr doped catalysts showed increased low temperature activity in the presence of NO/O 2 while the effect was less pronounced in case of Nd -doped samples. FTIR data has shown that the catalysts interact differently to NO/O 2 mixtures in that they do not form significant quantities of adsorbed nitrite-type species. We postulate that this species is a precursor to NO 2 formation which in turn increases soot combustion.
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