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.

Abstract: Multi-stage catalytic systems and methods are provided for converting NO.sub.x, CO, and hydrocarbons in a mixture, to innocuous products. The systems include first and second stages, each with substrate and catalyst. The mixture is contacted with the first stage for conversion of the major portion of the NO.sub.x and a portion of the CO and hydrocarbons. The output is contacted with the second stage to for conversion of CO and hydrocarbons. In one system, the first stage catalyst consists essentially of rhodium and a zeolite; the second stage catalyst comprises a noble metal including platinum and/or palladium, and a support. The mixture has a mole ratio of reducing to oxidizing agents of at least 0.8. Low ammonia is generated. In another system, the first stage substrate is made of material capable of being heated to at least 150.degree. C. in no more than about 20 seconds, has heating means for doing same, and is at this temperature at least part of the time of contact with the mixture.