Exhaust Gas Purifying Apparatus and Exhaust Gas Purifying Method

Abstract

The apparatus comprises a lean burn engine, a Pd catalyst 1 placed in exhaust gas from the lean burn engine and formed by loading a high concentration of Pd in the range of 3% by weight or more on a porous oxide, and enriching means 32 for temporally making an exhaust gas atmosphere around the Pd catalyst a rich atmosphere. It is believed that NO is oxidized into NO2 on the Pd catalyst 1 in the exhaust gas in a lean atmosphere and that NO2 originally existing in the exhaust gas and NO2 generated are adsorbed on Pd. This reaction occurs at low temperatures of about 200° C. to about 300° C., and thereby NOx are stored on the Pd catalyst 1. Therefore, NOx can be reduced and purified in a low temperature range from 200° C. to 300° C. without using a NOx storage material comprising an alkaline component.

Dependencies are inferred from the claim text.