Patent ID: 7465690

Claim:
A method for making a diesel particulate filter, comprising: providing a wall-flow substrate comprising an inlet channel and an outlet channel and a porous wall separating the inlet channel and the outlet channel, said porous wall comprising an inlet wall surface adjacent the inlet channel and an outlet wall surface adjacent the outlet channel, said wall-flow substrate being characterized by a thickness between the inlet wall surface and the outlet wall surface and by pores having an average pore size between 5 micrometers and 500 micrometers; applying a promoter oxide compound onto refractory inorganic oxide particles by forming a first slurry of the refractory inorganic oxide particles dispersed in a solution containing a precursor of the promoter oxide compound and calcining to form the promoter oxide compound and deposit the promoter oxide compound onto the refractory inorganic oxide particles, thereby forming supported promoter particles; impregnating the supported promoter particles with a noble metal catalyst to form catalyst-bearing particles; sizing the catalyst-bearing particles to an average particle diameter of about 2 micrometers to about 10 micrometers, wherein the particle size is about 10% to about 80% of the average pore size; applying the sized catalyst-bearing particles to the inlet wall surface of the wall-flow substrate and not to the outlet wall surface, said catalyst-bearing particles being applied by applying a second slurry comprising the sized catalyst-bearing particles and calcining to cause said catalyst-bearing particles to penetrate within the pores of the porous wall to a distance not greater than about 25% of the thickness of the porous wall.