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

A century of trends in adult human height

Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5-22.7) and 16.5 cm (13.3-19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8-144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries

Are ionic liquids an alternative for gas sweetening?

Natural Gas (NG) undergoes several treatment steps aiming to remove undesirable components such as carbon dioxide (CO2) and hydrogen sulfide (H2S), which are known as acid gases. A gas sweetening process is commonly performed by chemical or physical absorption. The latter is usually preferred when large amounts of acid gas should be removed because of the less energy demanding regeneration step. Ionic liquids (ILs) have been proposed as alternative solvents for numerous chemical processes due to properties such as chemical stability and negligible vapour pressure. Extensive research has been executed on the solubility of CO2 in ILs. It was found that CO2 is highly soluble in certain ILs. This fact encouraged us to propose ILs as an alternative solvent for CO2 capture. The aim of this work is to study the thermodynamic aspects of the feasibility of using ILs for CO2 separation from natural gas. The solubility of CO2, CH4 and other light hydrocarbons in the low-viscosity 1-hexyl-3-methylimidazolium tetracyanoborate ionic liquid ([hmim][TCB]) has been experimentally determined using a synthetic method (a Cailletet equipment) at temperatures up to 400 K and pressures up to 15 MPa. The solubility of CO2 in [hmim][TCB] has been found to be up to 20 times higher than the solubility of CH4. Interestingly, while the solubility of CO2 is highly dependent on the temperature, the solubility of CH4 in the IL is almost not influenced by temperature. Also it will be discussed why Henry’s law underestimates selectivities at elevated pressures. The binary P,T phase diagram of ethane and propane in [hmim][TCB] shows maximum solubility near the respective critical points of the two gases. It was observed that both hydrocarbons have a lower solubility than CO2 in [hmim][TCB]. However, there is a clear tendency that the higher the alkyl chain of the hydrocarbon, the higher is the solubility in [hmim][TCB]. Therefore, it is possible to find the optimum conditions to maximize the absorption of CO2 and minimizing the absorption of CH4 and other hydrocarbons

Solubility of carbon dioxide in the low-viscosity ionic liquid 1-hexyl-3-methylimidazolium tetracyanoborate

The solubility of carbon dioxide (CO2) in a new low-viscosity and non-fluorinated ionic liquid, 1-hexyl-3-methylimidazolium tetracyanoborate ([hmim][TCB]), has been studied experimentally using a synthetic method. Bubble point pressures (up to 12.34 MPa) of the system CO2 + [hmim][TCB] are reported for CO2 concentrations ranging from 10.09 to 70.16 mol% and within a temperature range of 283.56–364.04 K. The experimental values of the density, the viscosity and the surface tension of [hmim][TCB] are also reported. The results obtained are compared to available CO2 solubility data and physicochemical properties of other 1-hexyl-3-methylimidazolium based ionic liquids in order to study the effect of the type of anion. It is found that [hmim][TCB] shows higher CO2 absorptive capacity (higher solubility) as well as faster CO2 mass transfer kinetics (lower viscosity), which makes this ionic liquid an attractive solvent for gas separation processe

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

Ionic liquids for CO2 separation. A gas solubility study

Background Unprocessed Natural Gas (NG) usually contains high amounts of the acid gases carbon dioxide (CO2) and hydrogen sulphide (H2S) and other heavier hydrocarbons such as ethane and ethylene (C2), propane (C3), butane (C4). Removal of acid gas from NG (gas sweetening process) is commonly done by chemical or physical absorption. Physical solvents are usually preferred when high concentration of acid gas is present as it is the case in the Arab Gulf reservoirs. Aim Ionic liquids have been proposed as alternative solvents for numerous chemical processes. In order to study the feasibility of using ionic liquids as solvents for gas sweetening, the solubility of CO2, CH4 and other hydrocarbons present in the NG should be studied. The aim of this work is to determine the selectivity of CO2 over CH4 using the low-viscosity ionic liquid 1-hexyl-3-methylimidazolium tetracyanoborate ([hmim][TCB]) as absorbent. Also, the absorption of other hydrocarbons in this solvent is studied. Methods The solubility of several gases in the ionic liquid [hmim][TCB] has been experimentally determined using a Cailletet equipment at temperatures up to 400 K and pressures up to 15 MPa. Results The solubility of CO2 in [hmim][TCB] has been found to be up to 10 times higher than the solubility of CH4.Interestingly, the solubility of CO2 is highly dependent on the temperature while the solubility of CH4 is practically not influenced by the changes in temperature. Therefore, it is possible to find the optimum conditions to maximize the absorption of CO2 while minimizing the content of CH4. In the same way, the recovery of the solvent is designed to maximize the recovery of CH4. C2 and C3 have lower solubility than CO2 in [hmim][TCB], but as the alkyl chain increases, they become more soluble in the ionic liquid. At certain conditions, the mixture reaches a liquid immiscibility area and a second liquid (almost pure hydrocarbon) is formed. Conclusions A high selectivity of CO2 over CH4 has been found for the ionic liquid [hmim][TCB]. Additionally, solubility of ethane and propane in the ionic liquid has been found to be lower than the solubility of CO2. In other words, ionic liquids may be an alternative as solvents for gas sweetening