Room Temperature Ionic Liquids for Mercury Capture from Flue Gas

Six room temperature ionic liquids (RTILs) were synthesized and tested as coatings for adsorbents for mercury capture from nitrogen at 160 °C. All six RTILs were thermally stable to temperatures above 160 °C. These RTILs were coated on mesoporous silica gel, and the fixed-bed mercury capture characteristics of these adsorbents were observed at 160 °C. Hg 0 capture appears to result from the formation of a complex involving Hg 0 and ions in the RTIL complex, and not from oxidation by the RTIL. The high observed oxidized mercury capacity for Cl − -based RTILs is believed to be due to greater dissociation of HgCl 2 in the RTILs that incorporate chloride anion. The higher hydrogen-bond basicity and dipolarity of these RTILs might underlie improved HgCl 2 dissociation. [bmim]Cl was identified as a promising RTIL for the simultaneous capture of elemental and oxidized mercury from the gas phase. A nanostructured chelating adsorbent with a coating of 25 wt % [bmim]Cl has an elemental mercury capacity of 10 mg/g and an oxidized mercury capacity of at least 38 mg/g.