PEROVSKITE CATALYTIC COMPOSITIONS HAVING CRYSTAL STRUCTURES AND CONTAINING METALS OF THE PLATINUM GROUP

摘要

1489785 Exhaust gas purification catalysts E I DU PONT DE NEMOURS & CO 10 Oct 1974 [10 Oct 1973 25 April 1974 26 April 1974] 43933/74 Heading B1E [Also in Division Cl] A catalytic compound has cations of metals in sites of Type A and of Type B with oxygen ions in the proportions ABO 3 and having a perovskite crystal structure wherein from 1% to 20% of the sites of Type B are occupied by ions of a platinum group metal, and the remaining Type B sites are occupied by ions of a non-platinum group metal having ionic radii between 0.4 and 1.4Š the Type A sites being occupied by cations of at least 2 different metals each occupying at least 1% of the Type A cation sites and the Type B sites exhibiting at least one of the following characteristics: (A) at least 5% of the non- platinum group Type B sites are occupied by ions of a metal of variable valency in a first valency and at least 5% are occupied by ions of the same metal in a second valency; (B) the platinum group metal ions are rhodium or palladium ions; (B) a major proportion of the non-platinum group Type B sites are occupied by aluminium ions; (D) the non- platinum group Type B sites are occupied by ions consisting essentially of trivalent iron; cobalt or nickel. Preferred compounds are of the formulae (Sr x La 1-x ) (Co 1-y Ru y )O 3 where y is 0.01-0.2 and (1-x) is 0.95 (1-y) to 0.5 (1-y) and (Sr x La 1-x ) (Co 1-y Pt y )O 3 , where y is 0.01-0.10 and (1-x) is 0.95 (1-y) to 0.5 (1-y). The catalysts may be supported. Reference is made to Specification 1489786.