Room Temperature Ionic Liquids for Mercury Capture from Flue Gas

• Published in: Industrial & engineering chemistry research 2008-11, Vol.47 (21), p.8396-8400
• Main Authors: Ji, Lei, Thiel, Stephen W, Pinto, Neville G
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Chemical engineering; Exact sciences and technology; General processes of purification and dust removal; Pollution; Prevention and purification methods; Separations
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie8008023

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. Hg0 capture appears to result from the formation of a complex involving Hg0 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 HgCl2 in the RTILs that incorporate chloride anion. The higher hydrogen-bond basicity and dipolarity of these RTILs might underlie improved HgCl2 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.