Method of controlling ammonia amount adsorbed in selective catalytic reduction catalyst and exhaust system using the same

An exhaust system comprising:

• an engine generating driving torque by burning mixture of air and fuel and exhausting exhaust gas generated at combustion process through an exhaust pipe;
• a reducing agent supplier mounted on the exhaust pipe downstream of the engine and adapted to inject urea or ammonia (NH3) into the exhaust gas, wherein the urea is decomposed into the ammonia;
• a selective catalytic reduction (SCR) catalyst mounted on the exhaust pipe downstream of the reducing agent supplier and adapted to absorb the ammonia and to reduce nitrogen oxide contained in the exhaust gas using adsorbed, injected or decomposed ammonia;
• a temperature sensor detecting temperature of the SCR catalyst;
• and
• a controller reading predicted maximum temperature of the SCR catalyst based on current temperature of the SCR catalyst after a predetermined time, determining a target adsorption amount of the ammonia based on the predicted maximum temperature of the SCR catalyst, and controlling amount of the urea or the NH3 injected from the reducing agent supplier based on the target adsorption amount of the NH3 and current adsorption amount of the NH3.