(a) Oven characteristics. The oven used for termally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C.
(b) Evaluation gas composition.
(1) A synthetic exhaust gas mixture is used for evaluating the effect of thermal stress on catalyst conversion efficiency.
(2) The synthetic exhaust gas mixture must have the following composition:
| Constituent | Volume percent |
Parts per million |
|---|---|---|
| Carbon Monoxide1 | 1 | |
| Oxygen | 1.3 | |
| Carbon Dioxide | 9 | |
| Water Vapor | 10 | |
| Sulfur Dioxide | 20 | |
| Oxides of Nitrogen | 280 | |
| Hydrogen | 3500 | |
| Hydrocarbon1 2 | 4000 | |
| Nitrogen = Balance |
1Alternatively, the carbon monoxide and hydrocarbon proportions of the mixture may be changed to 1.2% and 4650 ppm, respectively (using on of these alternative concentrations requires that the other be used simultaneously).
2Propylene/propane ratio = 2/1.
[61 FR 52102, Oct. 4, 1996; 62 FR 20066, Apr. 24, 1997]
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