NOx storage properties of Pt/Ba/Al model catalysts prepared by different methods
Résumé
The influence of a pre-treatment at 700°C, either under a O2/N2 mixture or only under N2, and followed by a hydrothermal aging at 700°C under wet air, was studied for Pt/Ba/Al NSR model catalysts prepared by different methods: (i) successive impregnation of Ba and Pt, (ii) co-addition of Pt and Ba and (iii) barium precipitation followed by Pt impregnation. The catalysts were evaluated by NOx storage capacity measurements and were characterized by N2 adsorption, XRD, CO2-TPD, H2 chemisorption and H2-TPR. The pre-treatment under N2 largely improves the NOx storage performance in the whole studied temperature range (200°C-400°C), with or without H2O and CO2 in the inlet gas. The better NOx storage properties of the catalysts treated under N2 before aging are due to (i) a higher NO oxidation activity (mainly linked to a higher platinum dispersion) (ii) a higher number of NOx storage sites resulting from a higher barium dispersion, and consequently to (iii) a higher Pt-Ba proximity.
Domaines
Catalyse
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NOx storage properties of Pt-Ba-Al prepared by different methods - N2 effect.pdf (338.88 Ko)
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