How SCR Works
Selective Catalytic Reduction uses basic chemistry to reduce NOx emissions through a process that is simple, extremely efficient, very reliable and safe. The major components of the process are hot exhaust, Diesel Exhaust Fluid and a catalytic converter.
Vaporized DEF and hot exhaust gases enter a catalytic converter located in the exhaust system after the diesel particulate filter. The catalytic converter contains a catalyst, which is a substance that causes or accelerates a chemical reaction, without being affected itself. [Catalysts are common in everyday life; for example, gasoline powered vehicles have used catalytic converters to control emissions for several decades.]
DEF is a solution of purified water and urea, an organic nitrogen compound that turns to ammonia when heated. When this urea and water solution is injected into the hot exhaust stream and comes in contact with the SCR catalyst, the ammonia created from urea reacts with NOx to form nitrogen and water vapor -- two clean and harmless components of the air we breathe.
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