PURPOSE: To obtain a catalyst maintaining its activity without destroying the perovskite type crystal structure even at a high temp. above a specified temp. by disposing a specified 1st layer on a carrier substrate and a 2nd layer contg. a specified multipole oxide on the 1st layer and carrying a noble metal in the 1st or 2nd layer.
CONSTITUTION: A 1st layer 4 contg. at least alumina and further contg. ZrO2 added or carried in the surface layer is disposed on a carrier substrate 2, a 2nd layer 6 contg. a multiple oxide having a perovskite type structure represented by the formula Ln1-xAxMO3 (where Ln is one or more kinds of rare earth metals other than Ce, A is Ce or one or more kinds of alkaline earth metals, M is one or more kinds of transition metals and 0<x<1) is disposed on the 1st layer 4 and a noble metal such as Pd 8 is carried in at least one of the 1st and 2nd layers 4, 6 to obtain the objective catalyst. By this structure, the noble metal is hardly sintered even at a high hemp. above 800°C in an amosphere in which exhaust gas varies and high purification activity can be maintained.
TANAKA HIROHISA
TAKAHASHI ICHIRO
SATOU HIRONORI
MATSUURA SHINJI
CATALER IND CO