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Cobalt-promoted palladium as three-way catalyst

Magnus Skoglundh (Kompetenscentrum katalys (KCK) ; Institutionen för teknisk kemi) ; Hanna Johansson (Institutionen för teknisk kemi) ; Lars Löwendahl (Institutionen för teknisk kemi) ; Kjell Jansson ; Leif Dahl ; Bernhard Hirschauer
Applied Catalysis B: Environmental (0926-3373). Vol. 7 (1996), 3-4, p. 299-319.
[Artikel, refereegranskad vetenskaplig]

Fifteen catalysts were prepared by intermittently impregnating alumina washcoats with water solutions containing La3+, Co2+ and PdCl42- ions/complex and calcining them at 550-820 degrees C. The catalysts were evaluated with respect to light-off performance, at stationary and transient feed gas stoichiometry, respectively, and redox characteristics, using NO/CO/C3H6/O-2/N-2 gas mixtures to simulate car exhaust. Alumina supported Pd exhibited three-way activity, i.e., simultaneous oxidation of CO and C3H6 and reduction of NO in a narrow interval around stoichiometric composition of the feed gas. Compared to Pd alone, addition of La or Co caused a widening of the interval under net reducing conditions. Addition of Co to Pd caused a significant increase in the activities for oxidation of CO and C3H6 under stoichiometric conditions. The conversions of CO and C3H6 started at about 100 degrees lower temperatures over Co-promoted Pd compared to unpromoted Pd. A marked increase in the activity for the reduction of NO at transient conditions was observed over Co-promoted Pd compared to unpromoted Pd. The catalysts were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy combined with energy-dispersive spectroscopy analysis, X-ray photoelectron spectroscopy (XPS), and specific surface area measurements. Only Co2+ could be detected by XPS in the surface layers of the Co-containing sample. A significant part of the cobalt is present in forms which can be oxidized and reduced under synthetic car exhaust conditions. These oxidizable/reducible cobalt sites are predominantly active for oxidation of CO and C3H6, hence promoting the reduction of NO over Pd by initiating these exothermic reactions in the catalyst.

Nyckelord: palladium; cobalt; carbon monoxide oxidation; nitric oxide reduction; exhaust gas catalysis

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Denna post skapades 2012-02-06. Senast ändrad 2017-09-14.
CPL Pubid: 154799


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Kompetenscentrum katalys (KCK)
Institutionen för teknisk kemi (1946-1998)


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