The effects of Cu/HZSM-5 on combined removal of Hg0 and NO from flue gas

The combined removals of Hg0 and NO over zeolite (HZSM-5 was chosen to use) modified by copper (Cu/HZSM-5) catalysts were studied under different simulated flue gas conditions. Compared with HZSM-5, Cu/HZSM-5 showed higher activity and performed a synergetic effect for the Hg0 and NO removal at 250 °C. But the excess of copper could cause destruction of the thin pore walls and blocking of internal porosity of the catalyst leading to decrease of the activity. A comparison between Cu/HZSM-5 of different silica to alumina ratios (SiO2/Al2O3 ratio) was also performed. The highest NO and Hg0 conversions were observed over the lowest SiO2/Al2O3 ratio. In addition, the experimental results indicated that there was a synergetic effect between HZSM-5 and copper for the removal of NO and Hg0 by accelerating the intermediate formation (NO2) and by strengthening the adsorption NO and Hg0 on the catalyst surface under the reaction conditions. Moreover, the effects of individual flue gas components on the removals of Hg0 and NO were examined. O2 in the flue gas had a positive effect on both Hg0 and NO removals. However, the presence of H2O and SO2 inhibited both Hg0 and NO removals.