Highly Selective Capture of CO₂ by Ether-Functionalized Pyridinium Ionic Liquids with Low Viscosity

Abstract

In this work, three kinds of ether-functionalized pyridinium-based ILs [E n Py]­[NTf2] with low viscosity were designed and synthesized and used for highly selective separation of CO2 from CH4. It was found that the ether groups play an important role on physicochemical properties and CO2/CH4 selectivity in these three ILs. Compared with the nonfunctionalized analogues [C m Py]­[NTf2], the viscosities of [E n Py]­[NTf2] are lower and obviously decrease with the increasing number of ether oxygen atoms. The presence of ether groups on the cation has weak impacts on CO2 solubility of the ILs, but it contributes to a much lower CH4 solubility, which leads to the great increase of CO2/CH4 selectivity using [E n Py]­[NTf2]. Moreover, CO2/CH4 selectivity in all investigated ILs greatly decreases with the increasing temperature due to the weaker temperature dependence of CH4 solubility. In addition, the thermodynamic properties including the Gibbs free energy, enthalpy, and entropy of CO2 and CH4 in these ILs were also obtained, and the CO2 and CH4 dissolution mechanisms were further analyzed. The results demonstrated that the gas–IL interaction plays a dominate role in CH4 solubility in the investigated ILs, but CO2 dissolution in ILs is determined by both the IL–gas interaction and free volume of ILs. This work will offer new insights into designing more competitive ILs for selective separation of CO2 from CH4.

Enhanced NH3 capture by imidazolium‐based protic ionic liquids with different anions and cation substituents

“…The solubility of NH 3 in ILs was measured using vapor liquid equilibrium (VLE) apparatus as shown in Fig. , as had been used in previous work , . The system was composed of a cylinder, a gas reservoir, an absorption cell, a vacuum pump, pressure sensors and valves.…”

“…During recent decades, ionic liquids (ILs) have emerged as new solvents in the field of gas separations owing to their outstanding properties, such as high thermal stability, negligible vapor pressures and tunable structures. [14][15][16][17][18][19][20][21][22] Therefore, the NH 3 absorption by ionic liquids has aroused interest around the world, and researchers have paid a lot of attention to the screening and designing of ILs to increase NH 3 solubility along with good desorption performance. Yokozeki 2 ] as an example and explained that hydrogen atoms of the cation played an important role in NH 3 absorption.…”

Ether-functionalized ionic liquid based composite membranes for carbon dioxide separation

“…Task-specic ionic liquids (TSILs), also called functionalized ionic liquids, can improve the CO 2 absorption capacity and the absorption selectivity by introducing suitable moieties (like amine, 26,27 ether, 28 and nitrile groups 29 ) to ILs. [30][31][32] Considered the hydroxyl groups and the ether groups in cellulose acetate (CA), etherfunctionalized pyridinium-based ILs should be compatible with CA, which can be benecial for improving CO 2 separation performance. Moreover, ILs with pyridinium cations are relatively cheaper, more biodegradable, and less toxic compared with imidazolium-based ILs.…”

Enhancement of CO2 capture performance of aqueous MEA by mixing with [NH2e-mim][BF4]

“…The density value of the mixed absorbents was between the density value of 30 22,34 while the viscosity of the absorbents was below 10 mPa s with n I of 0-0.6, which showed that the addition of 30 vol% solution reduced the viscosity of absorbents signicantly. According to Fig.…”