Three-way catalysts (TWC's) are employed in the exhaust treatment for gasoline-fueled vehicles to achieve simultaneous control of CO, hydrocarbons (HC's) and NO emissions. A typical TWC contains precious metals (Pt, Pd, or Rh) and metal oxides which are beneficial for stability of the catalyst support (..gamma..-alumina) or enhancement of the catalyst activity under dynamic operating conditions. When the TWC is used in vehicles with closed-loop control of the air/fuel (A/F) ratio near the stoichiometric point for the control of the exhaust emissions, its performance has been found, in general, to be better than predicted from steady-state catalyst efficiency. This improved performance relates to several characteristic processes occurring under dynamic operating conditions, including oxygen storage, water-gas shift (WGS) reaction, and HC retention on the catalyst. The authors note here salient observations from a study of the dynamic behavior of a monolith TWC with the ultimate goal to obtain quantitative descriptions of the transient reactions involved. 17 references.
[1]
G. Somorjai,et al.
Leed and thermal desorption studies of small molecules (H2, O2, CO, CO2, NO, C2H4, C2H2 AND C) chemisorbed on the rhodium (111) and (100) surfaces
,
1977
.
[2]
R. L. Klimisch,et al.
The dual state behavior of supported noble metal catalysts
,
1974
.
[3]
W. Rothschild,et al.
Oxygen storage capacity of monolith three-way catalysts
,
1985
.
[4]
H. C. Yao,et al.
Ceria in automotive exhaust catalysts: I. Oxygen storage
,
1984
.
[5]
Jack C. Summers,et al.
The effects of SO2 on the performance of noble metal catalysts in automobile exhaust
,
1979
.