A low-viscosity family of ionic liquids based on the tetracyanoborate anion for CO2 capture

The extraordinary properties of ionic liquids (ILs) such as their negligible vapor pressure have placed them in the spotlight of researchers as alternative solvents for separation processes. The large number of anion/cation combinations allows the possibility of "designing" ILs according to the specifications required for the process. ILs should be chemically and thermally stable. When used for gas purification and carbon dioxide (CO2) capture, ILs are required to have a high CO2 absorption capacity and low viscosity. The newly task-specific ILs achieve higher CO2 loadings at moderate pressures, also at supercritical conditions. However, the relatively high viscosity of some ILs is a drawback for their practical application, in spite of their high gas solubility. The aim of this work is to study the feasibility of using tetracyanoborate-based ionic liquid for CO2 capture. The main characteristic of this family of ILs is their low viscosity compared to "traditional" ionic liquids, such as tetrafluoroborate or hexafluoroborate. We will present some pure component properties such as viscosity, density and surface tension, as well as solubility measurements of the binary systems IL+ CO2. The solubility of CO2 in 1-ethyl-3-methylimidazolium tetracyanoborate [emim][TCB] and 1-hexyl-3-methylimidazolium tetracyanoborate [hmim][TCB] was measured using the Cailletet apparatus where the bubble point was visually determined. The encouraging results show that the tetracyanoborate ionic liquids have a large potential for CO2 absorption applications

A low-viscosity family of ionic liquids based on the tetracyanoborate anion for CO2 capture

The extraordinary properties of ionic liquids (ILs) such as their negligible vapor pressure have placed them in the spotlight of researchers as alternative solvents for separation processes. The large number of anion/cation combinations allows the possibility of "designing" ILs according to the specifications required for the process. ILs should be chemically and thermally stable. When used for gas purification and carbon dioxide (CO2) capture, ILs are required to have a high CO2 absorption capacity and low viscosity. The newly task-specific ILs achieve higher CO2 loadings at moderate pressures, also at supercritical conditions. However, the relatively high viscosity of some ILs is a drawback for their practical application, in spite of their high gas solubility. The aim of this work is to study the feasibility of using tetracyanoborate-based ionic liquid for CO2 capture. The main characteristic of this family of ILs is their low viscosity compared to "traditional" ionic liquids, such as tetrafluoroborate or hexafluoroborate. We will present some pure component properties such as viscosity, density and surface tension, as well as solubility measurements of the binary systems IL+ CO2. The solubility of CO2 in 1-ethyl-3-methylimidazolium tetracyanoborate [emim][TCB] and 1-hexyl-3-methylimidazolium tetracyanoborate [hmim][TCB] was measured using the Cailletet apparatus where the bubble point was visually determined. The encouraging results show that the tetracyanoborate ionic liquids have a large potential for CO2 absorption applications

Solubility of carbon dioxide in the ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate

Recently, the use of ionic liquids (ILs) for gas separation processes has attracted much attention because of the high solubility of different gaseous species in ILs. This contribution presents new experimental measurements of the carbon dioxide (CO2) solubility in the IL 1-ethyl-3 methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]). This solubility has been determined by measuring the bubble point pressures of the binary mixture of [emim][FAP] + CO2 for CO2 concentrations ranging from (10.03 to 60.00) mol % and within a temperature range of (283.75 to 364.13) K using a synthetic method. The obtained values are compared to the solubilities of CO2 in other 1-ethyl-3-methylimidazolium based ILs, to study the effect of the anion. This comparison shows that the solubility of CO2 in the various ILs decreases in the order: [emim][FAP] > [emim][Tf2N] > [emim][EtSO4] = [emim][PF6] > [emim][BF4]. Therefore, the use of [emim][FAP] results in highest absorptive capacity, which makes this IL an attractive solvent for gas separation processes

The ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate as alternative extractant for BTEX separation

Previously, we proved that the ionic liquid (IL) 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]) is a promising candidate for natural gas sweetening. The reason is that the absorption capacity for CO2 is high, the selectivity for CO2/CH4 is good, and the IL shows low affinity for light hydrocarbons (CH4, C2H6, C3H8 and C4H10). In this study, capability of this IL for the extraction of aromatics from aliphatic + aromatic mixtures via liquid–liquid extraction is evaluated. Therefore, the solubilities of the liquid aliphatic hydrocarbons (hexane, heptane) and the liquid aromatic compounds (benzene, toluene, ethylbenzene, o-xylene (= BTEX)) in [emim][FAP] have been measured at different temperatures. The ternary liquid–liquid equilibrium (LLE) data for the ternary systems {hexane + benzene + [emim][FAP]}, {heptane + toluene + [emim][FAP]}, {octane + ethylbenzene + [emim][FAP]} and {octane + o-xylene + [emim][FAP]} have been measured at T/K = 293.15 and atmospheric pressure. The solute distribution coefficient and selectivity have been calculated and analyzed. The influence of the chain length (both in the hydrocarbon and in the aromatic) has been studied. Moreover, in order to properly evaluate the capability of this IL for BTEX recovery, the experimental data have been compared with available data in literature. Finally, the experimentally determined LLE data have been correlated using the NRTL model. It was found that the studied IL show distribution coefficient and selectivities compared to other ILs