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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.

Ceria nanofibers were synthesized as soot oxidation catalysts. The morphology of the catalyst was tailored to maximize the contact between the soot particles and the catalyst. Of the synthesized catalysts, the fibrous shape was the most active toward soot oxidation: the peak combustion temperature was reduced from 600°C (non-catalytic combustion) to 375°C during tight contact, 428°C during prolonged loose contact (see detailed definition in the text), and 553°C during loose contact. These results were compared to a very active ceria catalyst generated using the Solution Combustion Synthesis method and characterized by its high porosity and SSA surface.

Molybdenum sulfide nanoparticles have been successfully obtained, for lubricant applications, by means of a wet chemical synthesis in an aqueous solution employing ammonium molybdate, citric acid and ammonium sulfide as the reactants. Some molybdenum-citrate complexes were formed and they reacted with the ammonium sulfide to form MoS₂ nanoparticles. Mo:citrate molar ratio was identified as being the most relevant of the synthesis parameters that affected the phase and morphology of the final products. The optimized nanopowders were softly agglomerated and amorphous, with a mean size of the primary particles of about 30 nm. The compatibility between the thus obtained MoS₂ nanopowders and some commercial after-treatment catalysts for diesel vehicle engines was tested. Diesel oxidation, soot combustion and ammonia-SCR de-NOx catalysts were considered as were the possible effects on the catalytic activity and their possible reaction to the MoS₂ additive.

Experimental work was carried out on a small displacement Euro 5 automotive diesel engine alternatively fuelled with ultra low sulphur diesel (ULSD) and with two blends (30% vol.) of ULSD and of two different fatty acid methyl esters (FAME) obtained from both rapeseed methyl ester (RME) and jatropha methyl ester (JME) in order to evaluate the effects of different fuel compositions on particle number (PN) emissions. Particulate matter (PM) emissions for each fuel were characterized in terms of number and mass size distributions by means of two stage dilutions system coupled with a scanning mobility particle sizer (SMPS). Measurements were performed at three different sampling points along the exhaust system: at engine-out, downstream of the diesel oxidation catalyst (DOC) and downstream of the diesel particulate filter (DPF). Thus, it was possible to evaluate both the effects of combustion and after-treatment efficiencies on each of the tested fuels.

The aim of this work is to analyze particle number and size distribution from a small displacement Euro 5 common rail automotive diesel engine, equipped with a close coupled aftertreatment system, featuring a DOC and a DPF integrated in a single canning. In particular the effects of different combustion processes on PM characteristics were investigated, by comparing measurements made both under normal operating condition and under DPF regeneration mode. Exhaust gas was sampled at engine outlet, at DOC outlet and at DPF outlet, in order to fully characterize PM emissions through the whole exhaust line. After a two stage dilution system, sampled gas was analyzed by means of a TSI 3080 SMPS, in the range from 6 to 240 nm. Particle number and size distribution were evaluated at part load operating conditions, representative of urban driving.

The loading of a DPF entails the need of trap regeneration by particulate combustion, whose efficiency and frequency are somehow affected by the way soot is deposited along the channels. The aim of this work is therefore the development of a new experimental methodology able to provide fundamental information about the soot loading process inside the DPF, in order to take advantage of this insight for DPF design and optimization purposes. Small lab-scale 300 cpsi DPF samples were loaded downstream of the DOC in an ad hoc designed reactor capable of hosting 5 samples, by diverting part of the entire flow produced by an automotive diesel engine at 2500 rpm × 8 BMEP, selected as representative of the most critical operating conditions for soot production during the New European Driving Cycle (NEDC).

La1-xAxNi1-yByO3 nanostructured perovskite-type oxides catalysts (where A = Na, K, Rb and B = Cu; x = 0, 0.2 and y = 0, 0.05, 0.1), also supporting 2% in weight of gold, were prepared via the so-called “Solution Combustion Synthesis (SCS)” method, and characterized by means of XRD, BET, FESEM-EDS and TEM analyses. The performance of these catalysts evaluated. The 2 wt.% Au-La0.8K0.2Ni0.9Cu0.1O3 showed the best performance with a peak carbon combustion temperature of 367°C and the half conversion of CO reached at 141°C. The same nanostructured catalyst, deposited by in situ SCS directly over a SiC filter and tested on real diesel exhaust gases, fully confirmed the encouraging results obtained on the powder catalyst.