Effect of Three Way Conversion Catalyst Operation on the Chemical State of Automotive Sulfur Emissions

Emission of SO₃ or of sulfates can be virtually eliminated from catalytically controlled vehicles by operation in three way conversion mode as well as by operation of oxidation catalysts without air pumps. Hydrogen sulfide is not detected during normal excursions into the rich air-fuel region.

Combined with the fact demonstrated by Volvo that vehicles equipped with Engelhard three way conversion catalysts meet or are lower than the 1975-76 California emission standards after 50,000 miles of driving, a viable solution exists for emission control of all pollutants including sulfates.