Use of ionic liquids as absorbents to separate SO2 in SO2/O2 in thermochemical processes to produce hydrogen

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/O2 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/ILs gmol) showed the highest SO2 solubility among the tested ILs at 50 °C and 0.67 atm PSO2PSO2. 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.