Absorption of No and No2 in caprolactam tetrabutyl ammonium halide ionic liquids

Abstract

To explore environmentally benign solvents for the absorption of NO and NO2, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO2 was measured at temperatures rangingfrom 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO2 in ionic liquids with various halide anions was observed, respectively: F > Cl and Br > Cl > F. Moreover, asthe temperatureincreased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility ofNO increased.Alternatively, the solubility of NO2 decreased as thetemperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactam increased from 2:1 to 6:1. The absorption and desorption of NO and NO2 was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO2. © 2011 Air & Waste Management Association.