Catalytic behaviour of metal based ZSM-5 catalysts for NOx reduction with NH3 in dry and humid conditions

Abstract

Some metals (Cu, Cr and Fe) based on zeolite (H-ZSM-5) catalysts were prepared by wet impregnation method. These were characterized by X-ray diffraction and surface area measurements. The reduction of NO by NH3 in the presence of O-2 with and without water vapour was determined over these catalysts. FTIR spectra of adsorbed species and TPD study indicate the formation of copper ammonia complex; chemisorption of NH3 and NOx is found on Cu-ZSM-5, whereas in the cases of Cr-ZSM-5 and Fe-ZSM-5, only NH3 chemisorption is observed.Cu-ZSM-5 showed better catalytic activity with water and was superior to other catalysts, which showed lower activity and moderate selectivity. The results indicated that the presence of O-2 helps in adsorbing more NO over Cu-ZSM-5. The mechanistic pathways of this proposed reaction are based on earlier findings and on those of the present investigation.