Local Structures and Catalytic Ammonia Combustion Properties of Copper Oxides and Silver Supported on Aluminum Oxides

The local structures and catalytic NH 3 combustion properties of copper oxides (CuO x ) and silver (Ag) catalysts supported on aluminum oxides (Al 2 O 3 ) were studied. In order to achieve high catalytic NH 3 combustion activity and high N 2 (low N 2 O/NO) selectivity, the preparation conditions for impregnated binary catalysts were optimized. In comparison with the single CuO x /Al 2 O 3 and Ag/Al 2 O 3, binary CuO x –Ag supported on Al 2 O 3 showed high performance for catalytic NH 3 combustion. Among the binary catalysts, sequentially impregnated CuO x /Ag/Al 2 O 3 exhibited the highest activity and N 2 selectivity. Because the combustion activity is closely associated with the Ag–Ag coordination number estimated from Ag K-edge XAFS, highly dispersed Ag nanoparticles supported on Al 2 O 3 are considered to play a key role in the low-temperature light-off of NH 3 . CuO x /Ag/Al 2 O 3 also showed higher N 2 (lower NO) selectivity for temperatures at which NH 3 conversion reached approximately 100%, indicating that the N 2 is directly produced from the NH 3 combustion reaction over CuO x /Ag/Al 2 O 3 . Based on several analyses, a reaction mechanism for catalytic NH 3 combustion over CuO x /Ag/Al 2 O 3 was finally suggested.