Patent ID: 8110275

Claim:
A mixed particle comprising: noble metal particles of a noble metal; first particles of one or more metal oxides selected from a group consisting of Al 2 O 3 , SiO 2 , ZrO 2 and TiO 2 ; and second particles of a metal oxide having a larger adsorptive interaction with said noble metal of said noble metal particles as compared with said metal oxide of the first particles, wherein said noble metal particles are carried by said second particles in a larger proportion than by said first particles, wherein said mixed particle has an average particle diameter of about 1 to about 5 μm, wherein said first particles and said second particles are both secondary particles, and wherein said first particles have an average particle diameter larger than an average particle diameter of said second particles, said average particle diameter of said first particles being about 0.5 to about 2 μm, said average particle diameter of said second particles being about 0.1 to about 1 μm.