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

Abstract

Developing absorbents with both high absorption capacity of H 2 S and large selectivity of H 2 S/CO 2 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 H 2 S 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 H 2 S can reach 0.546 mol mol 21 (1 bar) and 0.225 mol mol 21 (0.1 bar), and the selectivity of H 2 S/CO 2 can reach 37.2 (H 2 S solubility at 1 bar vs. CO 2 solubility at 1 bar) and 15.4 (H 2 S solubility at 0.1 bar vs. CO 2 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 H 2 S from CO 2 .

Highly selective absorption separation of H2S and CO2 from CH4 by novel azole‐based protic ionic liquids

“…This is because the [DBNH][1,2,4‐triaz] can hydrolyze to produce [OH] − in the presence of water. [OH] − can react with CO 2 to form [HCO 3 ] − ; this trend is in agreement with the [BDMAEEH][Tf 2 N] + water + CO 2 systems 18 . The absorption capacity of H 2 S in [DBNH][1,2,4‐triaz] with 3.5 wt% H 2 O is lower than that in pure [DBNH][1,2,4‐triaz].…”

“…As for the unit of mol/kg, the solubility of H 2 S is as highs as 6.2 mol H 2 S/kg IL, being dozens of times higher than those in normal ILs and VOCs 26–34 . Moreover, it is also significantly higher than functionalized ILs reported in literatures . The selectivities of H 2 S/CO 2 in azole‐based PILs range from 4.6 to 7.5 for S 1/1 and from 3.0 to 4.7 for S 0.1/1 , which are comparable or superior to other ILs.…”

“…However, they suffered from high viscosity and complex synthesis procedures, which disfavored their industrial applications. Tertiary amine group have good affinity toward to H 2 S. We further synthesized a class of hydrophobic tertiary amine functionalized half protonated PILs paired with Tf 2 N as anion for highly selective absorption of H 2 S from CO 2 18 . The hydrophobic character will reduce regeneration expense.…”

Thermodynamic and molecular insights into the absorption of H2S, CO2, and CH4 in choline chloride plus urea mixtures

“…They are ionic compounds with melting points below or near room temperature, and have many unique properties such as extremely low volatility, wide liquid range and structural designability . Therefore, ILs are believed to be promising alternatives to traditional solvents for gas separation, and a number of studies have been dedicated to the design of IL‐based absorbents for CO 2 capture and natural gas upgrading . Unfortunately, the practical application of ILs is quite limited due to their high cost.…”

Metal nanoparticles in ionic liquid‐cosolvent biphasic systems as active catalysts for acetylene hydrochlorination

“…NPs@IL systems have been extensively applied in various catalytic reactions with excellent stability and activity, such as the olefin hydrogenation, biomass conversion, alcohol oxidation, electrochemical reaction . In addition, the remarkable dissolving capacity of ILs for gases, organic compounds, and polymers can sometimes activate substrates and thus improve the catalytic efficiency. Despite these favorable attributes, the viscosity of ILs is usually dozens to hundreds of times higher than that of organic solvents, which largely limits their applications .…”