1997-05-01

Measurement of Hydrogen Sulfide Formation at the Exhaust of Three-Way Catalyst Cars Using an Original Semi-Continuous Method - Evaluation of the Key Parameters 971611

Hydrogen sulfide released in the exhaust of gasoline fueled cars equipped with three-way catalysts and related odor troubles result from rich driving conditions (e.g. acceleration) following a storage of sulfur oxides on the catalyst during lean conditions (mid-speed cruise).
In order to evaluate the key parameters of this phenomenon, five different european cars were tested on a chassis dynamometer. An original semi-continuous hydrogen sulfide analysis method was designed for this purpose.
The test method was developed using an industrial H2S analyzer with a lead acetate impregnated paper tape. Hydrogen sulfide present in exhaust gas reacts with lead acetate and forms lead sulfide with a brown color. H2S content in the exhaust gas is measured by colorimetry using a photoelectric cell.
Reaction rate allows an H2S measurement every two seconds. This method allows the recording of high level hydrogen sulfide release peaks.
Using a testing procedure designed to clean catalysts, to store sulfur and to release H2S, tests were run with fuel containing from 35 to 900 ppm sulfur.
Test cars were equipped with different fuel injection systems, various air-fuel ratio strategies and catalyst formulations.
Most catalyst technologies are sensitive to the H2S release phenomenon. Air-fuel ratio strategies during stable speed and transient conditions appear to be the most important parameters.
With cars sensitive to H2S and for sulfur contents in gasoline below 500 ppm, the hydrogen sulfide release is approximately a linear function of the gasoline sulfur content. Other parameters are catalyst formulation and driving conditions (temperature, gas flow, duration).

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 43% off list price.
Login to see discount.
Special Offer: With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.
X