| 摘要 |
A three-way catalyst for use in the purification clarification of an exhaust gas discharged from an internal combustion engine wherein combustion is controlled in the vicinity of a stoichiometric atmosphere, which comprises an additive oxide comprising an oxide of at least one metal selected from Bi, Sn and Zn, in an amount of 0.02 to 0.2 moles per 1 liter of the volume of the catalyst. The above additive oxide converts SO2 into SO3 or SO4 in an oxidizing atmosphere, and stores a sulfur component as a sulfide in a reducing atmosphere, resulting in the inhibition of the discharge of H2 S. The above catalyst is free of Ni or Cu, each being a load to the environment and thus can be safely used, and also can inhibit the formation of H2S in a stoichiometric or reducing atmosphere.
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