Effects of support materials and silver loading on catalytic ammonia combustion properties

In this research, the effects of support materials and silver (Ag) loading on catalytic NH3 combustion properties were studied. Among the Ag supported on various metal-oxide materials, Ag/Al2O3 exhibited high catalytic NH3 combustion activity and high N-2 (low N2O center dot NO) selectivity. The combustion activity is closely associated with the Ag dispersion which is estimated using the O-2-H-2 titration technique. Thus, highly dispersed Ag nanoparticles on supports play a crucial role in the low-temperature light-off of NH3, implying that the support materials significantly affect the Ag dispersion. Although Ag/Al2O3 with higher amounts of Ag loading tended to exhibit higher combustion activity, the optimum Ag loading was found to be approximately 10 wt.%. At the optimum Ag loading concentration, Ag/Al2O3 performed well during the catalytic NH3 combustion reaction. The local structures of the catalysts were investigated via transmission electron microscopy, X-ray absorption fine structure and gas adsorption techniques. After an NH3 combustion reaction at a temperature of 900 degrees C, Ag/Al2O3 slightly deactivated because of the sintering of metallic Ag nanoparticles and the decreased surface area.