Highly efficient and selective H2S capture by task-specific deep eutectic solvents through chemical dual-site absorption

Abstract

• Novel task-specific DESs endowed with chemical dual sites were firstly developed. • [C 1 -TMHDA]Ac-MDEA (1:2) can achieve 1.44 mol/mol at 313.2 K and 1.0 bar. • Tertiary amine and acetate anion form dual chemical interactions with H 2 S. • These DESs can be reused for five times with negligible performance loss. Highly efficient and selective H 2 S capture is of great scientific significance for natural gas sweetening. However, there was seldom research concerned about the chemical absorption of H 2 S in deep eutectic solvents (DESs) and the absorption capacity is hard to be satisfactory. In this work, we propose a new strategy of designing task-specific DESs endowed with chemical dual sites for H 2 S capture. Therefore, four task-specific DESs bearing with tertiary amine and acetate anion, including [C 1 -TMHDA]Ac-MDEA (1:2), [C 1 -TMHDA]Ac-Pyrol (1:2), [C 1 -TMHDA]Ac-AA (1:2), and [C 1 -TMHDA]Ac-Im (1:2), were designed and prepared. Among them, [C 1 -TMHDA]Ac-MDEA (1:2) showed the unprecedented H 2 S absorption capacity of 1.44 mol/mol at 313.2 K and 1.0 bar, surpassing all the reported absorbents. The interaction mechanism was elucidated by both spectroscopic analysis and quantum chemical calculations. In addition, five consecutive absorption–desorption cycles were performed and evaluated the recyclability of [C 1 -TMHDA]Ac-MDEA (1:2) by heating and evacuating. Compared with other absorbents, these task-specific DESs represent prominent superiority on both H 2 S absorption capacity and H 2 S/CO 2 selectivity, which are expected to be excellent alternatives in the field of acid gas separation.