Abstract: This method comprises bringing exhaust gas from an internal combustion engine, which is operated at a fuel-lean air/fuel ratio, in contact with an iridium-containing catalyst in a first zone and then in contact with a platinum-containing catalyst in a second zone situated downstream of the first zone. This method is effective for exhaust gas from lean burn engines over a wide temperature range of 200 to 500.degree. C., produces less N.sub.2 O in a low-temperature range of 200 to 300.degree. C., and can purify exhaust gas stably and effectively even at a high temperature of 700.degree. C. or over.

Abstract: A catalyst for purifying exhaust gas, comprising a zeolite carrier having a mole ratio of SiO.sub.2 /Al.sub.2 O.sub.3 of from 20 to 200, and a compound oxide of copper and silicon supported on the carrier. The catalyst has high activity for elimination of nitrogen oxides (NO.sub.x) even in the presence of both oxygen and water vapor, and also has excellent durability at high temperatures. The catalyst is therefore effective in eliminating nitrogen oxides from exhaust gases from automobiles, boilers and the like.