Harendra S. Gandhi

Automotive exhaust catalysis

Abstract Research in the field of automotive exhaust catalysis has paralleled the broader growth in heterogeneous catalysis research—beginning in the 1960s, progressing through commercialization in the mid-1970s, and continuing today. The general trend has been one of increasingly complex catalyst formulations in response to increasingly stringent emission standards. Nowhere is this more evident than in the various means that have been employed to most effectively utilize the noble metal components. These efforts will continue, but with greater emphasis on optimizing catalyst formulations for lean-burn applications and reducing catalyst cost and complexity without sacrificing performance.

Characterization of Pd/γ-alumina catalysts containing ceria

The effects of adding CeO2 to PdAl2O3 as a catalyst modifier were investigated by X-ray photo-electron spectroscopy and X-ray diffraction. Catalytic effects were demonstrated by using propane oxidation as a model reaction. It was found that CeO2 promotes oxidation of Pd to PdO both with and without alumina. High-temperature reduction (⋍920 °C) and the presence of Pd are required for the total conversion to bulk CeAlO3 from CeO2Al2O3. Pd also assists in the oxidation of bulk CeAlO3 to CeO2 at elevated temperatures. In ambient air, Pd facilitates surface oxidation of CeAlO3 to CeO2, whereas surface Pd acquires an oxidation state between Pd0 and PdO. On PdAl2O3 the propane oxidation rate is found to be lowered by CeO2 if the oxygen concentration exceeds that of the Stoichiometric ratio.