Abstract
Durability tests were made on three types of catalytic converters for automotive exhaust gas. A 10, 000 km driving test was given to nine test cars equipped with a market-sold catalyst for oxidation of CO and HC. The average purification efficiencies of Pt catalyst and Pd-Cr catalyst were found to be 95.0% for CO and 76.2% for HC, and 60.9% for CO and 60.2% for HC, respectively.
Cu catalyst, however, showed the worst efficiency, 60.0% for CO and 51.0% for HC, and the decrease of catalyst weight. The property changes of the catalyst between before and after the use were examined by X-ray diffraction, fluorescent X-ray, BET, differential thermoanalysis, and a hardness meter. The hardness decreased to 1/4 of the fresh, which caused attrition to release the catalyst to the air. The detorioration of the catalytic activity seemed to depend on the crystal structure changes, the decrease of the specific surface area, and adsorption of Pb.
