Measurement of Automotive Catalyst Washcoat Loading Parameters by Microscopy Techniques
| Autor: | H.K. Plummer, R.J. Jr., R.H. Baird, A.A. Hammerle, J.D. Adamczyk |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
chemistry.chemical_classification
geography geography.geographical_feature_category Materials science Scanning electron microscope Energy conversion efficiency Analytical chemistry law.invention Catalysis Hydrocarbon chemistry law Microscopy Calcination Hydraulic diameter Monolith Composite material Instrumentation |
| Zdroj: | Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada. 5(4) |
| ISSN: | 1435-8115 |
| Popis: | Washcoat loading on automotive exhaust catalysts is normally determined, in production, by a weight gain procedure, which gives an accurate measure of washcoat weight present on an individual catalyst but does not address such parameters as uniformity of washcoat loading and geometric surface area within the monolith. Both issues are important factors that affect the catalytic activity (especially during catalyst lightoff) and catalyst cost (due to a thick, less functional washcoat) in an automotive exhaust system. Washcoat loading also plays a role in post-use analysis to determine possible reasons for changes (i.e., loss) in catalytic activity. For the post-use examinations weighing techniques are not useful since the washcoat cannot be preferentially removed and part of the weight gain is due to contamination from the combustion process. In the present work a combination of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) X-ray mapping, light microscopy, and digital image processing was used. Two methods have been demonstrated for the determination of the density of calcined alumina washcoats. Additionally, a method has been developed to determine catalyst washcoat loading, either on a sampling basis after manufacture or in studies of catalysts after use. Methods also have been developed to determine other important parameters such as monolith wall thickness, percent open area in a catalyst monolith, geometric surface area, and hydraulic diameter. A linear correlation has been shown between hydrocarbon conversion efficiency and measured geometric surface area, with a coefficient of determination (r2) of 0.84. |
| Databáze: | OpenAIRE |
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