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The deactivation of noble metal oxidation catalysts by lead and halide lead scavengers was studied in engine and laboratory experiments. The halide scavengers caused rapid but completely reversible inhibition of the catalyst activity, which existed only as long as the halide was present. The effects of catalyst temperature and noble metal concentration indicated that the halide scavenger dissociated upon adsorption on the catalyst. Palladium and platinum-palladium catalysts were more susceptible to halide inhibition than were platinum catalysts. Lead alone or lead plus scavengers produced a persistent poisoning of the catalyst. Lead poisoning effects were increased by increased catalyst temperatures and fuel lead content. Tests with scavengers only, conducted in an engine previously operated on leaded fuel, showed that lead was transported to the catalyst causing lead poisoning even in the absence of lead in the fuel.

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.

A new aluminum alloy bearing material containing lead-base babbitt is described. This material provides the performance advantages of an overplated babbitt construction without requiring the plating procedure. Performance characteristics including fatigue, wear, score, and corrosion resistances and embedability are compared to standard SAE bearing materials on the basis of laboratory tests. Extensive engine dynamometer and vehicle field tests are described to show the excellent durability of this new material.