Use of ionic liquids as absorbents to separate SO2 in SO2/O-2 in thermochemical processes to produce hydrogen

Abstract

In the thermochemical cycles such as the SI (sulfur-iodine) cycle, the Westinghouse process, and Ispra Mark 13 process, SO2 needs to be separated and purified to enhance system efficiency. As novel absorbents with non-volatility, thermal stability and high SO2 absorption capability, the characteristics of ionic liquids (ILs) as SO2 absorbents were investigated to separate SO2 in SO2/O-2 gaseous mixtures from the sulfuric acid decomposer. SO2 absorption and desorption experiments showed that SO2 solubility and absorption rate in ILs were influenced mainly by anions of ILs. [BMIm][Cl] and [BMIm][OAc] (1.40-1.69 SO2 gmol/lLs gmol) showed the highest SO2 solubility among the tested ILs at 50 degrees C and 0.67 atm P-SO2. Interestingly, [BMIm][OAc] showed irreversibility in the cycle of absorption and desorption. [BMIm][MeSO4] showed moderate SO2 solubility and good reversible cycles of absorption and desorption. The dependency of temperature and pressure on SO2 solubility of [BMIm][MeSO4] was scrutinized. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.