Copper Oxides Supported on Aluminum Oxide Borates for Catalytic Ammonia Combustion

Abstract

The catalytic NH3 combustion properties and local structures of copper oxides (CuOx) supported on aluminum oxide borates (Al20B4O36, 10Al2O3·2B2O3: 10A2B) were studied by means of high-angle annular dark-field scanning transmission electron microscopy, energy dispersive X-ray mapping, X-ray absorption fine structure, X-ray photoelectron spectroscopy, gas adsorption techniques, etc. Among the CuOx supported on various metal oxide materials, CuOx/10A2B exhibited high catalytic NH3 combustion activity, highest N2 (lowest N2O·NO) selectivity, and high thermal stability. Because the combustion activity is closely associated with the reducibility and dispersion of CuOx, highly dispersed CuOx nanoparticles on supports are considered to play a key role in the low temperature light-off of NH3. For NO and N2O selectivities, the oxidation state of CuOx and the dissociative species of adsorbed NH3 are suggested to be important catalytic combustion properties, respectively. On the basis of these discussions, the reaction mechanism of catalytic NH3 combustion over CuOx/10A2B is described.