§ 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:

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

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.

[61 FR 52102, Oct. 4, 1996; 62 FR 20066, Apr. 24, 1997]