A Kinetic Study of NO Oxidation and NOx Storage on Pt/Al2O3 and Pt/BaO/Al2O3
Journal article, 2001

Modeling and flow reactor experiments were used to study the kinetics of NO, storage/release on a Pt/BaO/Al2O3 model catalyst. The mechanism for this concept can be divided into four steps: (i) NO to NO2 oxidation on Pt, (ii) NO2 storage on BaO, (iii) NO, release, and (iv) NO, reduction to N2. In this paper, we have focused on the first three steps. From the NO oxidation study on Pt/Al2O3 compared to Pt/BaO/Al2O3, we observed that the presence of BaO decreases the formation of NO2. To test the importance of this step for effective storage, experiments were performed with a Pt/Al2O3 catalyst placed before the Pt/BaO/Al2O3 catalyst. This resulted in increased NO, storage for the combined system compared to the Pt/BaO/Al2O3 case. To resolve the second and third steps, an experimental investigation of NOx storage/release on BaO/Al2O3 was performed using only NO2 and N2 in the gas feed. We propose a kinetic model, which first includes adsorption of NO2, which oxidizes the surface, followed by nitrate formation. Finally, NO3-BaO-NO2, i.e., Ba(NO3)2, is formed. By using the kinetic parameters from the NO oxidation on Pt/BaO/Al2O3 and the NO, storage on BaO/Al2O3, a kinetic model was constructed to describe NO, storage/release experiments on Pt/BaO/Al2O3. However, the rate for NO, release was increased when Pt was present, and the kinetic model could not accurately describe this phenomenon. Therefore, the mechanism was modified by including a reversible surface spillover step of NO2 between Pt sites and BaO sites. Further, experiments with NO2 exposure followed by a temperature ramp with NO/N2 showed that the desorption behaviors from the BaO/Al2O3 and Pt/BaO/Al2O3 were significantly different, which further supports the spillover mechanism. Finally, the models describing NO, storage on BaO/Al2O3 and on Pt/BaO/Al2O3 were successfully validated with independent experiments.

TEMPERATURE

STICKING

REDUCTION

PT(111)

OXYGEN

ADSORPTION

DESORPTION

DECOMPOSITION

CO

3-WAY CATALYST

Author

Louise Olsson

Competence Centre for Catalysis (KCK)

Department of Chemical Reaction Engineering

Hans Persson

Competence Centre for Catalysis (KCK)

Chalmers, Applied Physics

Erik Fridell

Competence Centre for Catalysis (KCK)

Chalmers, Applied Physics, Chemical Physics

Magnus Skoglundh

Department of Applied Surface Chemistry

Competence Centre for Catalysis (KCK)

Bengt Andersson

Department of Chemical Reaction Engineering

Competence Centre for Catalysis (KCK)

Journal of Physical Chemistry B Materials

1089-5647 (ISSN)

Vol. 105 29 6895-6906

Driving Forces

Sustainable development

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Transport

Energy

Materials Science

Subject Categories

Chemical Engineering

DOI

10.1021/jp010324p

More information

Created

10/7/2017