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The activity and the mechanism of the main reactions in the NO/NO 2 -NH 3 SCR reacting system were comparatively investigated over a Fe-and a Cu-promoted commercial zeolite catalyst for the aftertreatment of Diesel exhausts. A dynamic micro-kinetic model in close agreement with all the details of the SCR catalytic chemistry was also developed.

The NO 2 -SCR reaction is studied by transient reaction analysis over a Fe-zeolite commercial catalyst. It is proposed that the NO 2 -SCR reaction occurs according to a mechanism wherein surface nitrates are first formed by NO 2 disproportionation, followed by their catalytic reduction to nitrogen by ammonia.

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Dispersions of a totally dispersible AlOOH powder have been studied. The effect of the initial composition has been studied to outline the reactions that determine the final rheological behaviour of the dispersions. The final viscosity and viscoelastic properties of the dispersions are determined by the sol-gel phenomena occurring during the ageing treatment. Gel formation is favoured by low water and high acid contents, while it is disfavoured by prolonged stirring. Gelling time from 48 h to 4 months has been observed depending on the initial composition.