What is the end product if DEF is used in conjunction with an SCR Catalyst in a diesel exhaust system?

What is the end product if DEF is used in conjunction with an SCR Catalyst in a diesel exhaust system?

• A. Oxygen and ammonia
• B. Nitrogen and water
• C. Carbon dioxide and water
• D. Hydrogen and water

Answer: (B)

DEF is a urea-water solution used to provide a reducing agent for the SCR catalyst. When injected into the hot diesel exhaust, urea hydrolyzes to ammonia, and the ammonia then reacts with nitrogen oxides over the SCR catalyst, converting NOx into nitrogen gas and water vapor. The ammonia is consumed in this process, so the net end products of NOx reduction are nitrogen and water. (Note that CO2 is released from the DEF itself during hydrolysis, but the active reduction products you’re evaluating are N2 and H2O.)

DEF is a urea-water solution used to provide a reducing agent for the SCR catalyst. When injected into the hot diesel exhaust, urea hydrolyzes to ammonia, and the ammonia then reacts with nitrogen oxides over the SCR catalyst, converting NOx into nitrogen gas and water vapor. The ammonia is consumed in this process, so the net end products of NOx reduction are nitrogen and water. (Note that CO2 is released from the DEF itself during hydrolysis, but the active reduction products you’re evaluating are N2 and H2O.)