| 摘要 |
PROBLEM TO BE SOLVED: To make up for a part of a chemical reaction required for removing a nitrogen oxide based on a rhodium catalyst by another catalyst and perform a chemical reaction, to begin with, at a low temperature without impairing the intrinsic performance of the rhodium catalyst by combining the catalyst containing a hardly reducible rhodium with a catalyst of a different composition from the former catalyst. SOLUTION: Ammonia water is dripped into an aqueous solution of a mixture of rhodium nitrate, gallium nitrate, zirconium nitrate and aluminum nitrate to produce an aqueous solution containing a coprecipitation product of rhodium, gallium, aluminum and zirconium. After that, the aqueous solution is thermally treated while it is heated/stirred and the obtained solution is filtered by suction to obtain a gel coprecipitation substance. At the same time, the coprecipitation substance is cleaned and dry-ground into fine powder, which is turn, is baked. A catalyst containing a hardly reducible rhodium obtained as described and a catalyst of a different composition from the former catalyst are combined to constitute the device. Further, the catalyst containing the hardly reduible rhodium is arranged in the downstream of the device and the catalyst of a different composition is arranged in the upstream. |
