Catalytic perovskites on perovskite supports and process for preparing them

A process for the preparation of catalytic compositions comprising applying a catalytically effective amount of at least one first metal oxide on a support of a second metal oxide, each of the first and second metal oxides having a perovskite crystal structure and a general formula, ABO.sub.3, the first metal oxide having A site cations comprising at least one metal selected from Group 2A, lanthanum and the lanthanide rare earth metals and having B site cations comprising at least one metal having an atomic number of 23 to 30, 42 to 47 or 74 to 79, the second metal oxide containing substantially equal numbers of metal cations in the A and the B sites, the A site cations being cations of at least one metal from Groups 1A, 1B, 2A, 3B, 4A, 5A and the lanthanide rare earth metals, the B site cations being cations of at least one metal from Groups 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6B, 7B, 8 and the lanthanide rare earth metals.