Automotive urea solution decomposes into NH at a certain exhaust temperature₃Under the action of SCR catalyst, NH₃Selective removal of NO from exhaust gas_xRestore to harmless N₂And H₂O， Realize deep denitrification of diesel engine exhaust.

There are two main types of SCR catalysts: V-SCR catalysts and molecular sieve SCR catalysts. The V-SCR catalyst can meet the national IV and V emission standards for diesel engine roads; Molecular sieve SCR catalysts are divided into Cu SCR and Fe SCR, which can meet the emission standards of diesel engine road VI and non road IV and above.

SCR catalysts can also be used for denitrification treatment of ships and fixed sources.

The V-SCR catalyst has good sulfur resistance and high conversion efficiency at medium temperatures, but it is prone to deactivation at high temperatures. Cu SCR catalyst has excellent low-temperature activity, wide temperature window, and excellent hydrothermal stability. Fe SCR catalyst exhibits excellent high-temperature activity.