91.329—Catalyst thermal stress test.
(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.
| Constituent | Volume percent | Parts per million |
|---|---|---|
| Carbon Monoxide 1 | 1 | |
| Oxygen | 1.3 | |
| Carbon Dioxide | 9 | |
| Water Vapor | 10 | |
| Sulfur Dioxide | 20 | |
| Oxides of Nitrogen | 280 | |
| Hydrogen | 3500 | |
| Hydrocarbon 1,2 | 4000 | |
| Nitrogen=Balance | ||
| 1 Alternatively, 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). | ||
| 2 Propylene/propane ratio=2/1. | ||