N2O formation in the selective catalytic reduction of NOx with NH3 on a CeMoOx catalyst

N2O formation over a CeMoOx catalyst in the selective catalytic reduction of NOx with NH3 has been investigated. N2O is formed above 300 degrees C over the catalyst samples. Non-selective NH3 oxidation (NSNO) and the non-selective NOx catalytic reduction (NSCR) reactions are recognized as the major pathways for N2O formation over CeOx and MoOx, respectively. With the presence of a small amount of MoOx in CeOx, e.g., 5 and 10 mol%, the formation of N2O is effectively suppressed, because the nonselective NH3 oxidation on CeOx is suppressed. However, the further increase of the MoOx content, e.g., up to 20 mol%, results in the formation of N2O in a large amount, because of the NSCR. The formation of surface polymeric octahedral molybdena species over Ce8Mo2Ox promotes the (NSCR) reaction. The presence of SO2 enhances the formation of N2O over (Ce8Mo2)Ox. However, the addition of H2O significantly suppresses the N2O formation, due to the inhibition of the deep cleavage of N-H bond in NH3, restraining the formation of N and NH species as a result. (C) 2015 Elsevier B.V. All rights reserved.