CATALYST FOR CLEANING EXHAUST GAS

摘要

PROBLEM TO BE SOLVED: To prepare a catalyst for cleaning exhaust gas for controlling the lowering of cleaning performance generated by the reaction of Rh with a carrier under the high temperature atmosphere of 900 deg.C or higher, keeping the Rh dispersion properties at the high level and improving heat resistance. SOLUTION: A catalyst for cleaning exhaust gas is composed of a first catalyst formed of a first porous carrier 1 carrying Rh and a second catalyst carrying at least one kind of Ph and Pd in a mixture of a second porous carrier 2 and a ceria-zirconia composite oxide 3, and the first porous carrier 1 is composed of θ-alumina of specific area of 50 m<2> /g or more. As θ-alumina is more excellent in stability at the high temperature than that of g-alumina, Rh is hard to dissolve in alumina crystals and also the sintering of Rh following the phase change and grain growth of alumina is controlled to maintain sufficiently the activities of Rh at the high temperature.