Structure characterization of aged automobile exhaust catalysts using electron probe microanalysis

Area of Science:

• Materials Science
• Catalysis
• Environmental Science

Background:

• Emission regulations drive advancements in automotive exhaust catalyst technology.
• Understanding catalyst deactivation mechanisms is crucial for extending service life.
• Microstructural characterization is vital for comprehending catalyst physicochemical properties.

Purpose of the Study:

• To characterize aged automobile exhaust catalysts.
• To identify deactivation causes in aged catalysts.
• To correlate deactivation mechanisms with reduced catalytic activity.

Main Methods:

• Analysis of aged automobile exhaust catalyst monoliths.
• Metallographic sample preparation using vacuum impregnation.
• Electron probe microanalysis for regional characterization.

Main Results:

• Identified thermal sintering leading to precious metal aggregation and alloying.
• Determined chemical poisoning by sulfur and phosphorus as major deactivation factors.
• Observed mechanical degradation, including washcoat loss and wear.
• Catalytic activity tests showed a significant decrease in the aged catalyst.
• Phosphorus negatively impacts CO oxidation, while sulfur accumulation affects propane oxidation.

Conclusions:

• The analysis method is significant for developing advanced washcoat materials.
• The method has potential for analyzing honeycomb catalysts in various industrial applications.
• This research contributes to extending the service life of emission control catalysts.