Search Results

During combustion, organosulfur compounds typically contained in gasoline are converted to SO2. Over automotive emission control catalysts, the SO2 can be converted to other sulfur compounds such as H2S,COS, and H2SO4. The chemistry of sulfur over catalysts is a function of A/F as well as catalyst composition. Exhaust emission control catalysts are also poisoned by exhaust SO2. The present study probes the extent of poisoning as a function of A/F, fuel sulfur levels and noble metal composition. The effect of fuel sulfur levels (14-6000 ppm) during aging and evaluation of platinum/rhodium, palladium/rhodium and palladium-only three-way control catalysts was evaluated. Performance measurements are reported for both engine dynamometer and vehicle systems.

A key element of diesel emission control is reduction of the particulate or soot that is emitted by diesel engines. These particulates are made up of a carbonaceous fraction, a volatile organic fraction, and a sulfate fraction. In this study, the role of flow-through oxidation catalysts on the control of each of these fractions is reported. Laboratory and vehicle studies were made to investigate the importance of catalyst washcoat and noble metal composition as well as vehicle operating conditions on the control of the various soot fractions. The effects of exposure of catalysts to high levels of sulfur were also examined. An optimized catalyst was found to provide good control of the volatile organic fraction and sulfate fraction of diesel particulate emissions. For control of sulfates, silica is preferred over alumina as the washcoat and palladium is preferred over platinum as the noble metal. At higher temperatures, release of sulfate is thermodynamically controlled to low levels.