Hydrogen Sulfide Formation Over Automotive Oxidation Catalysts
A number of laboratory and engine dynamometer studies were conducted to determine the effect of various catalyst and engine operating parameters on the formation of H2S over alumina-supported Pt and Pd catalysts. These experiments indicate that H2S formation occurs at high temperatures under O2 deficient conditions. The fraction of exhaust gas SO2 converted to H2S was relatively constant for various fuel sulfur levels, and thus H2S formation decreases as fuel sulfur content decreases. Calculation of thermodynamic equilibria, as well as various experimental results, indicate that H2S formation is kinetically limited under the experimental conditions investigated. Since the operating conditions that favor H2S formation (high catalyst temperature and O2 deficiency) do not normally occur in current oxidation catalytic emission control system operation, the formation of H2S over automotive oxidation catalysts is unlikely unless engine or system malfunctions occur.