Selective Oxidation of NH₃ to N₂ over Cu Catalysts Supported on MFI-type Metallosilicate

Abstract

Copper catalysts supported on MFI-type metallosilicate were prepared and their activities for selective oxidation of NH₃ were examined. Among the catalysts tested in this study, copper catalysts supported on MFI-type metallosilicate showed the highest activity. This catalyst selectively converted NH₃ to N₂ at 250–400 °C in the presence of excess oxygen.
The characterization of acidity and the effect of copper content revealed that active site of the catalyst in selective oxidation of NH₃ was the copper supported on the strong acidic site of metallosilicate. From NH₃–TPD, NH₃–O₂ pulse reaction and FT-IR measurements, amino groups formed on the catalyst surface were found to be intermediates of the NH₃ selective oxidation. The following mechanism for the selective oxidation of NH₃ was suggested; NH₃ is first adsorbed on the Brønsted acid site of metallosilicate and then converted to NH₄⁺. Secondly, dinitrogen group intermediate is formed by the oxidative dehydration of NH₄⁺. Finally, dinitrogen group intermediate is dehydrated oxidatively to N₂.