In an SCR system, a reductant such as ammonia is injected into the exhaust stream before it passes through the SCR catalyst. The catalyst facilitates the following chemical reactions: \[ 4NO + 4NH_3 + O_2 \rightarrow 4N_2 + 6H_2O \] \[ 2NO_2 + 4NH_3 + O_2 \rightarrow 3N_2 + 6H_2O \] These reactions efficiently convert NOx into nitrogen and water, significantly reducing NOx emissions.
