Cobalt-promoted palladium as three-way catalyst
Artikel i vetenskaplig tidskrift, 1996

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.

cobalt

exhaust gas catalysis

carbon monoxide oxidation

nitric oxide reduction

palladium

Författare

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 (ISSN) 1873-3883 (eISSN)

Vol. 7 3-4 299-319

Drivkrafter

Hållbar utveckling

Styrkeområden

Nanovetenskap och nanoteknik

Transport

Energi

Materialvetenskap

Ämneskategorier

Kemiteknik

DOI

10.1016/0926-3373(95)00049-6

Mer information

Skapat

2017-10-08