Process for utilizing doubly promoted catalyst with high geometric surface area

A method of converting noxious components of exhaust gas to innocuous entities, said noxious components comprising carbon monoxide, hydrocarbons, and nitrogen oxides, which comprises contacting said gases with a catalyst comprising a solid, transitional alumina extrudate support structure having a cylindrical, hollow annular configuration with internal reinforcing vanes, a nitrogen surface area of at least 50 m.sup.2 /g;

• a diameter of up to about 6.5 mm;
• an aspect ratio of the length to the diameter of from about 1 to 5;
• a geometric surface area of at least 25% greater than a hollow tube of the same inside and outside diameter;
• a porosity of at least 0.3 cm.sup.3 /g;
• a surface area per reactor volume of at least 5 cm.sup.2 /cm.sup.3, and deposited directly on the support structure without having any washcoat present from about 1-10 wt. % ceria, an alkali metal promoter expressed as the wt. % of the oxide M.sub.2 O in an effective amount up to about 5% and a catalytically-effective amount of one or more platinum group metals.