Hydrophobic protic ionic liquids tethered with tertiary amine group for highly efficient and selective absorption of H2S from CO2

Developing absorbents with both high absorption capacity of H2S and large selectivity of H2S/CO2 is very important for natural gas sweetening process. To this end, a class of novel hydrophobic protic ionic liquids (ILs) containing free tertiary amine group as functional site for the absorption of H2S were designed in this work. They were facilely synthesized through a simple neutralization-metathesis methodology by utilizing diamine compounds and bis(trifluoromethylsulfonyl)imide as the building blocks for cation and anion, respectively. Impressively, the solubility of H2S can reach 0.546 mol mol(-1) (1 bar) and 0.225 mol mol(-1) (0.1 bar), and the selectivity of H2S/CO2 can reach 37.2 (H2S solubility at 1 bar vs. CO2 solubility at 1 bar) and 15.4 (H2S solubility at 0.1 bar vs. CO2 solubility at 1 bar) in the hydrophobic protic ILs at 298.2 K. Comparing the hydrophobic protic ILs with other absorbents justifies their superior performance in the selective absorption of H2S from CO2. (c) 2016 American Institute of Chemical Engineers AIChE J, 62: 4480-4490, 2016