NOx storage in barium-containing catalysts
Journal article, 1999

The effect of key parameters on the characteristics of barium oxide-based NOx storage catalysts was systematically investigated. Model Pt/BaO/Al2O3, BaO/Al2O3, Pt–Rh/Al2O3, and Pt–Rh/BaO/Al2O3 catalysts were prepared and evaluated with respect to NOx storage capacity using transient flow reactor studies, temperature-programmed desorption studies (TPD), and in situ Fourier transform infrared (FTIR) absorption spectroscopy. The influence of temperature, storage and regeneration times, NOx source (NO or NO2), oxygen concentration, reducing agent (C3H6, C3H8, CO, or H2), and carbon dioxide concentration onNOx storage capacity was studied. Significant amounts of NOx were found to be stored in the catalysts containing both barium oxide and noble metals. For these catalysts the following observations were made: (1) maximum NOx storage was observed at about 380C; (2) around this temperature no significant differences between NO and NO2 on NOx storage capacity could be observed; (3) a slow increase in stored NOx could be observed with increasing oxygen concentration during the lean phase; (4) significant NOx desorption peaks, mainly of NO, were observed immediately after the switch from lean to rich conditions; and (5) at about 380±C the in situ FTIR spectra show characteristic nitrate peaks in the region 1300–1400 cm¡1 when NOx was stored under lean conditions and isocyanate peaks around 2230 cm-1 when the catalysts were regenerated under rich conditions in the presence of hydrocarbons. The step leading to stored NOx is believed to involve NO2 and the presence of atomic oxygen. During the rich period, the noble metal surfaces are probably reduced, leading to breakthrough peaks when NO desorbs.

SELECTIVE REDUCTION

3-WAY CATALYST

OXYGEN

METAL-CATALYSTS

NITROGEN-OXIDES

EXHAUST

ENGINE

Author

Erik Fridell

Chalmers, Applied Physics, Chemical Physics

Competence Centre for Catalysis (KCK)

Magnus Skoglundh

Department of Applied Surface Chemistry

Competence Centre for Catalysis (KCK)

Björn Westerberg

Department of Chemical Reaction Engineering

Competence Centre for Catalysis (KCK)

Stefan Johansson

Competence Centre for Catalysis (KCK)

Chalmers, Applied Physics

Gudmund Smedler

Competence Centre for Catalysis (KCK)

Department of Chemical Reaction Engineering

Journal of Catalysis

0021-9517 (ISSN) 1090-2694 (eISSN)

Vol. 183 2 196-209

Driving Forces

Sustainable development

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Transport

Energy

Materials Science

Subject Categories

Chemical Engineering

DOI

10.1006/jcat.1999.2415

More information

Created

10/7/2017