Effect of the Active Metal on the NOx Formation during Catalytic Combustion of Ammonia SOFC Off-Gas

Catalytic combustion of hydrogen and ammonia containing off-gas surrogate from an ammonia solid oxide fuel cell (SOFC) was studied with a focus on nitrogen oxides (NOx) mitigation. Noble and transition metals (Pt, Pd, Ir, Ru, Rh, Cu, Fe, Ni) supported on Al2O3 were tested in the range of 100 to 800 degrees C. The tested catalysts were able to completely convert hydrogen and ammonia present in the off-gas. The selectivity to NOx increased with reaction temperature and stagnated at temperatures of 600 degrees C and higher. At low temperatures, the formation of N2O was evident, which declined with increasing temperature until no N2O was observed at temperatures exceeding 400 degrees C. Over nickel and iridium-based catalysts, the NOx formation was reduced drastically, especially at 300 to 400 degrees C. To the best knowledge of the authors, the current paper is the first study about catalytic combustion of hydrogen-ammonia mixtures as a surrogate of an ammonia-fed SOFC off-gas.

Automated summary

The catalytic combustion of hydrogen and ammonia-containing off-gas surrogate from an ammonia solid oxide fuel cell (SOFC) was studied. The results showed that the tested catalysts were able to completely convert hydrogen and ammonia present in the off-gas. The formation of nitrogen oxides (NOx) increased with reaction temperature and stagnated at temperatures of 600 degrees C and higher.