<P> Overall, this is </P> <Dl> <Dd> (NH 2) 2CO + H 2O → 2 NH 3 + CO </Dd> </Dl> <Dd> (NH 2) 2CO + H 2O → 2 NH 3 + CO </Dd> <P> From this point, ammonia, in the presence of oxygen and a catalyst, will reduce nitrogen oxides: </P>

Where does the urea in def come from