Novel nano-structured sorbents for elemental and oxidized mercury removal from flue gas

Thermally robust chelating adsorbents, 3-mercaptopropyltrimethoxysilane silica (MPTS-silica) and 3-aminopropyltiethoxysilane 2-mercaptobenzothialzole silica (APTS-MBT-silica), were proven to be very effective in capture HgCl 2 from simulated flue gas at elevated temperatures in a fixed-bed mode. For MPTS-silica, a minimum of 58 mg/g HgCl2 capacity was observed. Pore size of the silica substrate does not have significant effect while particle size was found to have a significant effect on mercury capture; this effect was believed to be due to an enhanced channeling effect for the larger particle size adsorbent.;A new approach for simultaneous removal of elemental and oxidized mercury from flue gas was successfully developed by using a room temperature ionic liquid (RTIL) coating layer. Six RTILs were synthesized and tested for their potential of elemental and oxidized mercury capture. These RTIL coating layers are all thermally stable above 160°C and the coating of these RTIL does not have any negative effect on the thermal stability of the chelating ligands. 1-butyl-3-methyl-imidazolium chloride ([bmim]Cl) was identified to be the most promising RTIL for simultaneous elemental and oxidized mercury removal from flue gas. 25 wt% [bmim]Cl coated MPTS-silica showed a 10 mg/g saturated elemental mercury capacity and a minimum of 38 mg/g oxidized mercury capacity in a fixed-bed mode.;A low temperature selective catalytic reduction (SCR) catalyst, manganese oxide supported on titania, was tested as a sorbent for elemental mercury capture from flue gas at high temperatures. It was shown that this material showed high mercury capacity and remained active for mercury capture even after use for NOx reduction. Water vapor and manganese loading do not have a significant effect on mercury capture. However, SO 2 has a strong negative effect on mercury removal process. Bed temperature was found to have a significant effect on mercury capture process. HgO formed during the mercury adsorption process by this material and it was believed that the mercury adsorption follows Mars-Maessen mechanism.