Effects of NO sub(2) and SO sub(2) on selective catalytic reduction of nitrogen oxides by ammonia

The selective catalytic reduction (SCR) characteristics of NO and NO sub(2) over V sub(2)O sub(5)-WO sub(3)-MnO sub(2)/TiO sub(2) catalyst using ammonia as a reducing agent have been determined in a fixed-bed reactor at 200-400 super(o)C. The presence of NO sub(2) enhances the SCR activity at lower temperatures and the optimum ratio of NO sub(2)/NO sub(x) is found to be 0.5. During the SCR reactions, there are some side reactions occurred such as ammonia oxidation and N sub(2)O formation. At higher temperatures, the selective catalytic oxidation of ammonia and the nitrous oxide formation compete with the SCR reactions. The denitrification (DeNO sub(x)) conversion decreases at lower temperatures but it increases at higher temperatures with increasing SO sub(2) concentration. The presence of SO sub(2) in the feeds inhibits N sub(2)O formation.