Catalyst compositions and methods of making the same

A method of making a catalyst composition comprising a platinum group metal catalytic component and an activated alumina stabilized against thermal degradation, the method comprising:

• (a) dispersing one or more platinum group metal catalytic components on an activated alumina;
• (b) combining a solid, particulate ceria with the activated alumina to form an alumina-ceria mixture;
• (c) applying a coating of the alumina-ceria mixture to a carrier substrate;
• (d) calcining the substrate coated with the alumina-ceria mixture to provide thereon an activated alumina-containing calcined coating;
• (e) after step (d), impregnating the calcined coating on the carrier with a solution of a stabilizer-precursor which upon calcination yields a stabilizer chosen from the group consisting of rare earth metal oxides, alkaline earth metal oxides, titania, zirconia, hafnia, silicon dioxide and mixtures thereof;
• and
• (f) calcining the stabilizer-precursor impregnated coating.

A method of making a catalyst composition comprising an activated alumina having one or more platinum group metal catalytic components dispersed thereon, comprising:

• (a) dispersing one or more platinum group metal catalytic components on particles of an activated alumina;
• (b) applying to a carrier substrate the activated alumina having said one or more platinum group metal catalytic components thereon, and calcining the resultant coating on the carrier substrate;
• and
• (c) carrying out steps (a) and (b) while limiting the exposure of the activated alumina to acid so that platinum, rhodium and palladium catalytic components, when one or more are present, each has a dispersion of at least about 0.3 carbon monoxide molecules per atom of platinum group metal as measured by CO chemisorption (i) the disperson of platinum and rhodium being measured after reduction in hydrogen at 750.degree. C. for one hour and (ii) the dispersion of palladium being measured after heating in air for one hour at 750.degree. C. followed by reduction in hydrogen at 350.degree. C. for one hour.