High surface area washcoated substrate and method for producing same

Abstract

A washcoated substrate and method for producing the washcoat on the substrate are disclosed which comprises forming a slurry comprising at least one ionizable compound of A, where A is selected from barium, strontium, and combinations thereof, and A is in an amount sufficient to yield AO in an amount of about 0.2-20% by weight of the washcoat, an aluminum oxide yielding species, and a medium wherein at least a portion of the ionizable compound ionizes to form ions of A, contacting the slurry with a substrate to form a green coating containing A and the aluminum oxide yielding species thereon, and heat treating the resulting green-coated substrate at a temperature and for a time sufficient to form a washcoat consisting essentially of AO-Al.sub.2 O.sub.3 on the substrate, wherein A is homogeneously distributed throughout the Al.sub.2 O.sub.3, the washcoat having a specific surface area, as measured by the N.sub.2 BET method, of at least about 50 m.sup.2 /g, which surface area remains after at least two repeated exposures of the washcoat to temperatures of greater than about 500.degree. C. Additionally, the slurry solid can be removed from the liquid, fired to form a material comprising AO-Al.sub.2 O.sub.3, and another slurry formed of the fired material and a medium. This slurry can then be contacted with a substrate to form the green coating which is then heat treated to form the washcoat.