| abstract |
1511333 Perovskite catalysts E I DU PONT DE NEMOURS & CO 25 April 1975 [25 April 1974 (2)] 17279/75 Heading C1A (Also in Division B1] In a Perovskite catalyst of formula ABO 3 , the Type A cation sites are substantially fully occupied by ions of one metal having an atomic number of 11-51,56-71 or 89-103; a portion of the Type B cation sites are occupied by ions of at least one Platinum group metal selected from Ru, Os, Rh, Ir, Pd and Pt, and the remaining Type B sites are occupied by the ions of at least one non-platinum group metal having an ionic radius between 0À4 and 1À4 Angstroms, and wherein the Type B sites exhibit one of the following characteristics: (A) at least 5% of the non-Pt group sites of Type B are occupied by ions of a metal of variable valence in a first valence and at least 5% of the non- Pt group sites of Type B are occupied by ions of the same metal in a second valence; (B) substantially all of the non-Pt group Type B site metals are present in a single valence and a major portion of the non-Pt group Type B site metals are present in a valence of 3: and provided that when the Type A metal is Ba and the Pt group metal is Pt, no more than 80% of the Type B sites are occupied by Ti. Examples disclose the use of Ba, K, La, Nd and Sr in Type A sites and Co, Cr, Cu. Fe, Mn, Mo, Nb, Ni, Ta, Ti, V and W in the non Pt-group Type B sites, in catalysts supported on alumina substrates in the oxidation of CO and propane and the reduction of NO x in nitrogen streams. |