91.329 Catalyst thermal stress test.§ 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.
(2) The synthetic exhaust gas mixture must have the following composition:
|Parts per million|
|Carbon Monoxide 1||1|
|Oxides of Nitrogen||280|
|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.