Study on the Hg⁰ and NH₃ oxidation performance of copper modified attapulgite catalysts

A copper-modified attapulgite (Cu₃-ATP) catalyst with both mercury oxidation and ammonia oxidation activities was prepared by an improved wet impregnation method. Several characterization including SEM, H₂-TPR and NH₃-TPD were performed on it, and its mercury oxidation and ammonia oxidation performance were tested at 150-400 ℃. The results show that the copper species is successfully loaded on ATP surface, which significantly improves the redox ability of the catalyst, increases the strong acid sites and partial strong acid sites on the surface, and thus promotes the oxidation of Hg⁰ and NH₃. HCl plays an important role in Hg⁰ oxidation. High temperature is not conducive to the Hg⁰ oxidation reaction, but can promote the oxidation of NH₃. At 350 ℃, the oxidation efficiencies of Hg⁰ and NH₃ over Cu₃-ATP are both above 90%. Experiments on the influencing factors show that NH₃ has an obvious inhibitory effect on mercury oxidation at high space velocity, while low concentrations of Hg⁰ and HCl have no significant influence on ammonia oxidation. When the gas hourly space velocity (GHSV) is lower than 5×10⁴ h^-1, Cu₃-ATP can simultaneously oxidize NH₃ and Hg⁰. In addition, the mercury oxidation reaction shows good sulfur resistance and water resistance, but SO₂ has a certain inhibitory effect on ammonia oxidation.