Nitrogen Oxide Removal Catalysts for Purification of Automobile Exhaust Gases

The chemistry involved in the selective catalytic reduction of oxides of nitrogen (NO_x) to nitrogen is outlined and the requirements of a practical NO_x reduction catalyst are summarized. The effects of temperature, gas composition, NO_x concentration, and sulfur dioxide on the activity of some potential NO_x catalysts have been studied. Steady-state engine dynamometer endurance runs with ruthenium and non-ruthenium catalysts are described, and some vehicle durability data with particulate and monolithic base metal containing NO_x catalysts are also presented.