Abstract: A catalyst for the emission control of aldehyde comprises a coat layer of zirconium oxide formed on a monolithic substrate and can efficiently control the emission of aldehyde in an exhaust gas discharged from an internal engine using alcohol fuel.

Abstract: A feedback type air-fuel ratio control system controls the air-fuel ratio of air-fuel mixture fed to an internal combustion engine in accordance with an information signal issued from a first oxygen sensor installed in an exhaust line of the engine. The exhaust line has a catalytic converter at a position downstream of the first oxygen sensor. There is further provided a system in the control system, which detects deterioration of the first oxygen sensor. The system comprises a computer and a second oxygen sensor of delayed response type installed in the exhaust line at a position upstream of the converter. The computer defines higher and lower slice levels with respect to the output of the second oxygen sensor and compares the output of the second oxygen sensor with the higher and lower slice levels.

Abstract: A catalyst for the purification of exhaust gas comprises a combination of palladium carried on cerium oxide and palladium carried on alumina, or further rhodium carried on alumina, in which a weight ratio of palladium carried on cerium oxide to palladium carried on alumina is 2:8-8:2. Preferably, the cerium oxide contains at least one of zirconium, lanthanum, neodymium and praseodymium, or the alumina contains at least one of zirconium, lanthanum, neodymium, cerium, strontium and barium. This catalyst develops excellent purification performances against exhaust gas of oxidizing atmosphere to reducing atmosphere.