Low activation energy pathway for the catalyzed reduction of nitrogen oxides to N2 by ammonia

A low activation energy pathway for the catalytic reduction of nitrogen oxides to N-2, with reductants other than ammonia, consists of two sets of reaction steps. In the first set, part of the NOx is reduced to NH3; in the second set ammonium nitrite, NH4NO2 is formed from this NH3 and NO + NO2. The NH4NO2 thus formed decomposes at -100degreesC to N-2 + H2O, even on an inert support, whereas ammonium nitrate, NH4NO3, which is also formed from NH3 and NO2 + O-2, (or HNO3), decomposes only at 312degreesC yielding mainly N2O. Upon applying Redhead's equations for a first order desorption to the decomposition of ammonium nitrite, an activation energiy of 22.4 is calculated which is consistent with literature data. For the reaction path via ammonium nitrite a consumption ratio of 1/1 for NO and NO2 is predicted and confirmed experimentally by injecting NO into a mixture of NH3 + NO2. owing over a BaNa/Y catalyst. This leads to a yield increase of one N-2 molecule per added molecule of NO. Little N-2 is produced from NH3 + NO in the absence of NO2.