Experimental Measurement of the Solubility and Diffusivity of CO₂ in Room-Temperature Ionic Liquids Using a Transient Thin-Liquid-Film Method

Abstract

In this paper, results from an experimental investigation of carbon dioxide (CO 2 ) solubility and diffusivity in the ionic liquids 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim], and 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]) are reported. A transient thin liquid film method was developed, which enables one to determine the Henry's law constant and the diffusivity at low pressure simultaneously. Measurements were performed at temperatures in the range of 283-323 K. Henry's law constants were in the range of 25.5-84 bar and were in general agreement with measurements reported by other researchers for these and similar ionic liquids. The entropies and enthalpies of absorption were determined to increase as gas solubility decreased. The measured CO 2 diffusion coefficients in the five ionic liquids were ∼10 -6 cm 2 /s, which is an order of magnitude smaller than the coefficients for CO 2 diffusion in traditional organic solvents. In contrast to the gas solubility results, measured diffusion coefficients were determined to be dependent on the ionic liquid cation as well as the anion. In addition, CO 2 diffusion coefficients were considerably more sensitive to temperature than were CO 2 solubilities in these ionic liquids. Results were used to develop a correlation relating CO 2 diffusion to ionic liquid properties and system temperature.

CO2 separation applying ionic liquid mixtures: the effect of mixing different anions on gas permeation through supported ionic liquid membranes

“…17,18 Consequently, several studies on the permeation properties of gases through SILM systems have explored the effect of the IL structure. Relating to the influence of the cation, a number of groups have investigated the gas permeation properties of different families of ILs (imidazolium, [19][20][21][22][23][24][25][26][27][28][29][30] phosphonium, 31,32 sulphonium, 32 pyridinium, 33 and ammonium 34 ) and improved results were obtained for imidazolium-based SILMs in terms of permeability and selectivity. Other studies, also focused on imidazolium ILs, explored different structural variations of the cation in order to enhance CO 2 solubility and selectivity.…”

Perspectives of Ionic Liquids Applications for Clean Oilfield Technologies

“…This process is expensive due to high energy consumption at desorption stage and loss of the amine during the treatment and amine recovery (Rao & Rbin, 2002). During the present century, a big number of studies have been performed to explore the prospects of ILs for gases separation and for founding the best prototypes for CO 2 capture (Bates et al, 2002, Baltus et al, 2004, Baltus et al, 2005, Shiflett & Yokozeki, 2005, Jacquemin et al, 2006, Hou & Baltus, 2007, . Schilderman et al, 2007, Yokozeki & Shiflett, 2007, Sánchez et al, 2007, Ventura et al, 2008, Camper et al, 2008, Soriano et al, 2008, Soriano et al, 2009, Heintz et al, 2009, a, b. Carvalho et al, 2009, Kuleman et al, 2010, Shokouhi et al, 2010 and also several discoveries have been patented (Brennecke & Maginn, 2002, Davis Jr., 2004, Chinn et al, 2006.…”

Gas-Expanded Lubricants for Increased Energy Efficiency and Control in Rotating Machinery

“…The diffusion of carbon dioxide into various fluids [48][49][50][51][52][53][54][55][56][57][58][59][60] and the diffusion of refrigerants into lubricant oils [40,[61][62][63][64] are described in the literature. Despite this effort, the diffusion of carbon dioxide into synthetic oils had yet to be reported.…”

“…Despite this effort, the diffusion of carbon dioxide into synthetic oils had yet to be reported. Hence, CO 2 diffusivity into a group of representative lubricants was measured using a modified pressure-decay method developed by Hou and Baltus [57]. Lubricant was added gravimetrically to a pressure vessel of known volume and dimensions.…”

“…Each pressure curve could then be fit by non-linear regression to Equation (2.1), derived from Fick's Law for one-dimensional diffusion, Henry's Law, and a mole balance of the gas column above the fluid film. The full derivation of Equation (2.1) can be found in [57]. …”