Mechanism study on H2S capture of ionic liquids based on triethylenetetramine blended with ethylene glycol

Abstract

Amino-functionalized ILs are promising absorbents for H2S. In this work, three triethylenetetramine functionalized ionic liquids (TETAH-ILs) were synthesized and applied to construct mixture solutions with ethylene glycol (EG). Among [TETAH][HCOO]-EG, [TETAH][BF4]-EG and [TETAH]Br-EG absorbents, [TETAH][BF4]-EG showed the greatest H2S absorption capacity. In addition, a series of factors, such as IL molar fraction, absorption temperature and H2S flow rate, were also investigated to evaluate the effects on absorption performance of [TETAH][BF4]-EG absorbent. The results showed that the 10 % [TETAH][BF4]-EG mixed solution has excellent absorption capacity (1.128 mol H2S/mol IL) at 303.15 K and 100 mL/min. In addition, the absorbent could remain 75.12 % absorption capacity after four regenerations, which displayed potential for reversibility. Furthermore, the mechanism of H2S absorption by TETAH-ILs was proposed by combining FT-IR and 1H NMR characterization and electron density topology analysis. Furthermore, the mechanism of H2S absorption by TETAH-ILs was proposed by combining FT-IR and 1H NMR characterization and theoretical calculation. The results revealed that the mechanism of H2S absorption by TETAH-ILs was the formation of IL-H2S complexes through a series of hydrogen bonds.