| 摘要 |
PURPOSE:To enhance poisoning resistance with regard to a poisoning substance, by making the pore size of fine pore size, which are present in the catalyst supporting layer on the surface of a catalyst base material, larger toward the surface layer side of the catalyst supporting layer and making the same smaller toward the inner layer part of said catalyst supporting layer. CONSTITUTION:Activated alumina having fine porous with an average pore size of 100Angstrom is applied to the surface of a monolithic catalyst base material 1 made of cordierite to form a first catalyst supporting layer 2. Subsequently, activated alumina having fine pores with an average particle size of 300Angstrom is applied to said first layer 2 to form a second catalyst supporting layer 3. Further, activated alumina having fine pores with an average core size of 500Angstrom is applied to the second layer 3 to form a third catalyst supporting layer 4 to obtain a monolithic catalyst base material. A platinum group metal such as Pt, Pd or Rh is supported alone or in combination by said catalyst base material to obtain a catalyst for purifying exhaust gas.
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