Abstract
Mn-Ce mixed oxides supported on commercial columnar activated coke (MnCe/AC) were employed to remove elemental mercury (Hg) at low temperatures (100-250 C) without the assistance of HC1 in flue gas. The samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Xray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Effects of some factors, including Mn-Ce loading values, active component, reaction temperatures and flue gas components (02, SO2, NO, H20), on Hg removal efficiency were investigated. Results indicated that the optimal Mn-Ce loading value and reaction temperature were 6% and 190 C, respectively. Considerable high Hg removal efficiency (>90%) can be obtained over MnCe6/AC under both N2102 atmosphere and simulated flue gas atmosphere at 190 C. Besides, it was observed that 02 and NO exerted a promotional effect on Hg removal, H20 exhibited a suppressive effect, and SO2 hindered Hg removal seriously when in the absence of 02. Furthermore, the XPS spectra of Hg 4f and Hg-TPD results showed that the captured mercury were existed as Hg and Hg0 on the MnCe6/AC, and Hg0 was the major species, which illustrated that adsorption and catalytic oxidation process were included for Hg removal over MnCe6/AC, and catalytic oxidation played the critical role. What's more, both lattice oxygen and chemisorbed oxygen or OH groups on MnCe6/AC contributed to Hg oxidation. MnCe6/AC, which exhibited excellent performance on Hg removal in the absence of HC1, appeared to be promising in industrial application, especially for low-rank coal fired flue gas. (C) 2015 Elsevier B.V. All rights reserved.