Preliminary studies of Pt/Rh-MgO/Al2O3 and Pt/Rh-MgO/CeO2/Al2O3 catalysts for storage and reduction of NOx in exhaust gases at rich and lean fuel mixture were performed. NOx conversion and time of reaching steady state for lean mixture was used for comparison of catalytic and sorption activity. Catalysts were prepared: first on the alumina pellets by impregnation process and second on steel honeycomb monolith with washcoat layer. The conversion of nitrogen oxides as a function of temperature and different time of lean period to rich was determined. Thanks to the results of these studies both catalysts were compared. The prepared bed reactor containing magnesia as NOxtrap oxidizes CO and HC and reduces NOx during cyclic changes of air to fuel mixtures. Oxidation and reduction properties of the reactor are strongly dependent on the cycle of mixture changes and temperature. Generally there is an average NOx conversion ratio decrease with the increase of lean period time. For monolith type of reactor Pt/Rh-MgO/CeO2/Al2O3 conversion didn not obtain acceptable results above 200oC for both SV values. The relation of the surface area to the volume of the reactor was higher for the monolith reactor than for the bed type.
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