Exhaust gas purifying catalyst and method for manufacturing the same

An exhaust gas purifying catalyst, comprising:

• a powder comprising a porous material having a specific surface area of 150 m2/g or more, cerium and platinum, cerium and platinum being loaded on the porous material,
• wherein the powder has platinum dispersion of 70% or more before baking and platinum dispersion of 50% or more after baking in air at 700° C., and
• a integrated intensity of a diffraction peak originating from a Pt (311) plane at a diffraction angle of:
• 2θ=81.37±0.2° is about zero in an X-ray diffraction measurement by use of a CuKα radiation after the baking.

A method for manufacturing an exhaust gas purifying catalyst, comprising:

• preparing an aqueous slurry containing a powder comprising a porous material having a specific surface area of 150 m2/g or more, cerium and platinum, cerium and platinum being loaded on the porous material;
• adjusting pH of the aqueous slurry to a range from 5.8 to 6.3 inclusive;
• applying the aqueous slurry having the adjusted pH to a thermal-resistant inorganic support;
• drying the support having the slurry applied thereto;
• and
• baking the support after the drying,
• wherein the powder has platinum dispersion of 70% or more before heating and platinum dispersion of 50% or more after heating in air at 700° C., and
• a reduction rate R of the platinum dispersion after the heating against the platinum dispersion before the heating is below 40%, the reduction rate R being represented by a following equation (1):
• R=(1−(Pt dispersion after heating)/(Pt dispersion before heating))×100 (1).

A method for manufacturing an exhaust gas purifying catalyst, comprising:

• (a) impregnating a powder of a porous material having a specific surface area of 150 m2/g or more with a cerium acetate solution, drying the powder, and then baking the powder;
• and
• (b) impregnating the powder with a tetraammine platinum hydroxide solution, drying the powder, and then baking the powder,
• wherein the powder is contained in the catalyst,
• the powder having cerium and platinum loaded thereon has platinum dispersion of 70% or more before heating and platinum dispersion of 50% or more after heating in air at 700° C., and
• a reduction rate R of the platinum dispersion after the heating against the platinum dispersion before the heating is below 40%, the reduction rate R being represented by a following equation (1):
• R=(1−(Pt dispersion after heating)/(Pt dispersion before heating))×100 (1).

A method for manufacturing an exhaust gas purifying catalyst, comprising:

• (a) impregnating a powder of a porous material having a specific surface area of 150 m 2/g or more with a mixed solution of a cerium acetate solution and both or any one of a zirconium acetate solution and a lanthanum acetate solution, drying the powder, and then baking the powder;
• and
• (b) impregnating the powder with a tetraammine platinum hydroxide solution, drying the powder, and then baking the powder;
• wherein the powder is contained in the catalyst,
• the powder having cerium, platinum and both or any one of zirconium and lanthanum loaded thereon has platinum dispersion of 70% or more before heating and platinum dispersion of 50% or more after heating in air at 700° C., and
• a reduction rate R of the platinum dispersion after the heating against the platinum dispersion before the heating is below 40%, the reduction rate R being represented by a following equation (1):
• R=(1−(Pt dispersion after heating)/(Pt dispersion before heating))×100 (1).

A method for purifying an exhaust gas, comprising:

• preparing an exhaust gas purifying catalyst comprising a powder including a porous material having a specific surface area of 150 m2/g or more, cerium and platinum, cerium and platinum being loaded on the porous material,
• wherein the powder has platinum dispersion of 70% or more before baking and platinum dispersion of 50% or more after baking in air at 700° C., and
• a reduction rate R of the platinum dispersion after the baking against the platinum dispersion before the baking is below 40%, the reduction rate R being represented by a following equation (1):
• R=(1−(Pt dispersion after baking)/(Pt dispersion before baking))×100 (1);
• and
• an internal combustion engine having the exhaust gas purifying catalyst installed thereon is driven repeatedly in an air/fuel ratio ranging from 10 to 50 inclusive.