Hg0 Removal from Simulated Flue Gas over CeO2/HZSM-5

Abstract

The effects of zeolite (HZSM-5 was chosen for use) modified by CeO2 (CeO2/HZSM-5) on the gas-phase elemental mercury (Hg0) removal were investigated under simulated flue gas. The Brunauer–Emmett–Teller surface area analyses, powder X-ray diffraction measurements, and thermogravimetric analyses were employed to characterize the samples. The experimental results showed that there was a synergetic effect between CeO2 and HZSM-5 on Hg0 removal. The acidic sites of HZSM-5 could effectively adsorb Hg0 from the flue gas, and CeO2 could significantly enhance the oxidation of adsorbed Hg0. However, the surface area of CeO2/HZSM-5 decreased because of excess CeO2, which was detrimental to its Hg0 removal efficiency. Moreover, the temperature tests manifested that 6% CeO2/HZSM-5 achieved high Hg0 removal efficiency at low reaction temperatures (<300 °C). Additionally, the Hg0 removal efficiencies of CeO2/HZSM-5 were found to be significantly affected by the flue gas components. In the presence of O2, promotional effects of NO and SO2 on the Hg0 removal were found, while the presence of H2O inhibited the Hg0 removal in this experiment. Furthermore, after regeneration, CeO2/HZSM-5 still possessed good reactivity and its Hg0 removal efficiency stayed above 92% in 30 h.