Tin oxide exhaust catalyst supports and catalysts stable at high temperatures
A tin-oxide based three-way catalytic material employing precious metals that is stable at exhaust gas temperatures of internal combustion engines when the tin oxide lattice includes any of several rare earth oxide stabilizers in the lanthanide series. The rare-earth elements are the 15 lanthanide elements with atomic numbers 57 through 71 that are in Group IIIA of the Periodic Table: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Such tin-oxide based catalytic materials may also beneficially include zirconium oxide and/or yttrium oxide. The invention is useful in providing three-way catalytic exhaust converters for internal combustion engines.
1. A chemical composition for supporting noble metal in an exhaust catalyst, said composition comprising tin oxide, zirconium oxide, cerium oxide, and lanthanum oxide.
2. A composition in accordance with claim 1 wherein said composition is suitable as a wash coat for subsequently receiving said noble metal to form said catalyst.
3. A composition in accordance with claim 1 further comprising an inert material having a high BET surface area.
4. A composition in accordance with claim 3 wherein said inert material includes aluminum oxide.
5. An exhaust gas catalyst, comprising a composition including tin oxide, zirconium oxide, cerium oxide, lanthanum oxide, and a noble metal selected from the group consisting of platinum, palladium, gold, silver, ruthenium, iridium, rhodium, and combinations thereof.