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Measurement of Automotive Catalyst Washcoat Loading Parameters by Microscopy Techniques
1Physics Department, Ford Research Laboratory, Mail Drop 3028, SRL, Dearborn, MI 48121-2053
Summary
New methods using microscopy and digital imaging accurately measure automotive catalyst washcoat loading and geometric surface area. This improves understanding of catalytic activity and cost, crucial for both production and post-use analysis.
Area of Science:
- Materials Science
- Chemical Engineering
- Automotive Engineering
Background:
- Traditional washcoat loading determination by weight gain lacks uniformity and geometric surface area data.
- Uniformity and surface area are critical for catalytic activity, lightoff performance, and cost-effectiveness.
- Weight gain methods are unsuitable for post-use catalyst analysis due to contamination and inability to remove washcoat selectively.
Purpose of the Study:
- To develop advanced methods for accurately assessing automotive exhaust catalyst washcoat loading.
- To evaluate washcoat uniformity and geometric surface area for improved catalytic performance insights.
- To establish reliable techniques for both manufacturing quality control and post-use catalyst examination.
Main Methods:
- Utilized a combination of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) X-ray mapping, light microscopy, and digital image processing.
- Developed and demonstrated methods for determining calcined alumina washcoat density.
- Created techniques to measure catalyst washcoat loading, monolith wall thickness, percent open area, geometric surface area, and hydraulic diameter.
Main Results:
- Established two methods for determining the density of calcined alumina washcoats.
- Developed a versatile method for assessing catalyst washcoat loading in both production and post-use scenarios.
- Quantified key structural parameters including monolith wall thickness, open area, geometric surface area, and hydraulic diameter.
- Demonstrated a strong linear correlation (r²=0.84) between hydrocarbon conversion efficiency and measured geometric surface area.
Conclusions:
- The developed imaging and processing techniques provide accurate and comprehensive characterization of automotive exhaust catalysts.
- These methods offer significant advantages over traditional weight gain procedures, especially for assessing uniformity and post-use conditions.
- Geometric surface area is a key predictor of catalyst performance, directly impacting hydrocarbon conversion efficiency.