Development of Non-Nickel Additives for Reducing Hydrogen Sulfide Emissions from Three-way Catalysts

Under certain operating conditions, automotive three-way catalysts can form hydrogen sulfide in concentrations sufficient to produce an offensive odor. Several additives from the ferrite group of compounds (M²⁺Fe₂O₄ where M = Ni, Co, Zn, Cu) have been determined to effectively reduce hydrogen sulfide emissions from three-way catalyst washcoats in laboratory tests. No alterations in the chemistry of the catalyst are required, and no detrimental effect on three-way activity is observed.