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A set of manganese oxide catalysts was synthesized and doped with Cu and/or Fe by means of the citric acid sol-gel preparation method. The samples were studied by means of several characterization techniques: field-emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), N2-physisorption at -196 °C, H2 and soot temperature-programmed reduction (H2-TPR, soot-TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of the prepared catalysts was investigated in the oxidation of a probe VOC molecule (propylene) and carbon soot singularly and simultaneously. The catalytic performances were studied as well assuring a content of 5 vol.% of water in the gaseous reactive mix. The investigations evidenced that the best soot catalytic oxidation rates occurred over the Mn2O3 sample, while the copper-doped manganese oxide (i.e. the MnCu15) showed the best performance in the decomposition of propylene.

In this work, several nanostructured ceria-based catalysts were prepared by the hydrothermal technique varying two synthesis parameters (namely, temperature and pH). Then, cerias with different shapes (i.e., cubes, rods, combination of them, other polyhedra) and structural properties were obtained. The prepared materials were tested for the CO oxidation and soot oxidation efficiency. The results have shown that, for the CO oxidation, activities depend on the surface properties of the catalysts. Conversely, for the soot oxidation, the most effective catalysts exhibit better soot-catalyst contact conditions.

A set of ceria-zirconia nanocatalysts with different Zr-contents and structural properties was prepared to study the effect of both the Zr-amount and surface-dependent activity towards soot combustion in “loose” and “tight” soot-catalyst contact. The properties of the catalysts were examined using several physico-chemical techniques. The best soot oxidation activities were achieved for the Ce0.9Zr0.1O2-NP catalyst (NP means nano-polyhedra and 0.9 indicates the atomic ratio of Ce/Ce+Zr), due to its easier reducibility, compared to high-surface area catalysts with the same Ce/Zr ratio. Moreover, better performances were reached for Ce0.9Zr0.1O2-NP, than similar nano-polyhedra with higher Zr-amounts (denoted as CexZr1-xO2-NP, where x = 0.8 or 0.7). On the other hand, worse activities were obtained for both mesoporous and microporous catalysts with the same Ce/Zr ratio.