New adsorbents for direct warm-gas capture of mercury

Abstract

A new class of adsorbents for direct capture of mercury from warm-gases has been developed. In these adsorbents, a dicarboxylic acid (DCA) is dissolved in a selective ionic liquid (IL) layer; the DCA + IL solution is coated on a mesoporous support. Mercury is absorbed by the IL and reacts with the DCA to form a halatopolymer, immobilizing the captured mercury. A prototype adsorbent was prepared by coating the IL [bmim]Cl and azelaic acid on mesoporous silica. Thermogravimetric analysis indicates that the adsorbent is thermally stable at the target operating temperature. Fixed-bed adsorption tests of elemental mercury capture from nitrogen at 160°C show that this adsorbent can capture 44 mg Hg⁰/g adsorbant. Leaching tests indicate that the captured mercury is held tightly by the adsorbent. The high mercury capacity and high adsorption temperature suggest that the prototype adsorbent is competitive with modified carbons currently used in integrated gasification combined cycle applications.