Solubility measurements of hydrogen in 1-butyl-3-methylimidazolium tetrafluoroborate and the effect of carbon dioxide and a selected catalyst on the hydrogen solubility in the ionic liquid V.A. Toussaint a , E. Kühne a , A. Shariati b , C.J. Peters c,d,⇑ a Delft University of Technology, Faculty of Applied Sciences, DelftChemTech, Julianalaan 136, 2628 BL Delft, The Netherlands b Shiraz University, School of Chemical and Petroleum Engineering, Molla Sadra Street, Shiraz 71345, Iran c The Petroleum Institute, Department of Chemical Engineering, Abu Dhabi, United Arab Emirates d Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separations Technology Group, P.O. Box 513, 5600 MB Eindhoven, The Netherlands article info Article history: Received 20 July 2012 Received in revised form 12 December 2012 Accepted 17 December 2012 Available online 8 January 2013 Keywords: Hydrogen Carbon dioxide Hydrogenation catalyst Ionic liquid Solubilities in binary and ternary systems abstract The high pressure phase behavior of a binary mixture containing hydrogen (H 2 ) and 1-butyl-3-methyl- imidazolium tetrafluoroborate ([bmim][BF 4 ]) is studied by measuring bubble-point pressures at different temperatures for three compositions with hydrogen mole fractions of 5, 7.5 and 10 mol%. Since this work is part of a study to design a hydrogenation process, using [bmim][BF 4 ] as the reaction medium, the effects of adding carbon dioxide (CO 2 ) or the hydrogenation catalyst (À)-1,2-bis((2R,5R)-2,5-dimethyl- phospholano)benzene (cyclooctadiene)rhodium(I) tetrafluoroborate (Rh-MeDuPHOS) on H 2 solubility in [bmim][BF 4 ] was measured as well. All measurements were conducted in an autoclave set-up, allowing pressures up to 60 MPa and temperatures ranging from 313.15 up to 368.15 K. Results indicated that the presence of catalyst increased the H 2 solubility in [bmim][BF 4 ] compared to those of binary mixtures of H 2 + [bmim][BF 4 ] throughout the whole temperature range studied. However, the addition of CO 2 to the binary system of H 2 + [bmim][BF 4 ] increases the H 2 solubility at lower temper- atures (<330 K), and decreases it at higher temperatures (>340 K). Ó 2013 Published by Elsevier Ltd. 1. Introduction Room temperature ionic liquids (RTILs) are molten salts that consist of an organic cation, and often of an inorganic anion. As the name suggests, they are usually in their liquid state at or near room temperature. Nowadays, more and more researchers are becoming interested in ILs due to some interesting properties that they possess. One of the main focal points for research is the use of ILs as solvents, especially as replacements for common volatile organic solvents. An important property of ILs in this respect is their negligible vapor pressure, which offers obvious advantages from an environmental point of view (minimization of solvent loss), a safety point of view (less working exposure hazards) and an economical point of view (less solvent loss by vaporization). Another important property is the large temperature range over which ILs remain liquid. A difference of 400 °C between the melt- ing point and decomposition point is not uncommon. Although, this feature of ILs can be affected by some different reasons such as water content and impurities of ILs. Brennecke and Maginn [1] gave an extensive perspective of potential industrial applications of ILs in catalytic reactions, gas separations, liquid-liquid extractions, electrolyte/fuel cells, as lubricants, and as heat transfer fluids. There are several studies in literature showing that it is possible to perform hydrogenation reactions using an IL as the solvent [2,3]. For example, Shariati et al. [4] experimentally investigated the pos- sibility of combining the advantages of ILs as solvents for hydroge- nation reactions and chiral catalysts for asymmetric reactions. They also studied the effect of CO 2 on the conversion and enanti- oselectivity of their selected reaction. Brennecke and coworkers showed the possibility of extracting solutes from ionic liquids using an additional supercritical phase [5,6]. Although this knowl- edge paved the way to perform hydrogenation reactions using ILs as solvents, more research is required to obtain a better under- standing of the behavior of such reaction systems and how to opti- mize them. For a number of systems containing ILs and supercritical fluids, the phase behavior has been examined by Blanchard et al. [7], An- thony et al. [8], Liu et al. [9], Perez-Salado Kamps et al. [10], Shariati and Peters [11–13], Costantini et al. [14], Bermejo et al. [15], Ren 0021-9614/$ - see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jct.2012.12.013 ⇑ Corresponding author at: Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ, P.O. Box 513, STO 1.21, 5600 MB Eindhoven, The Netherlands. E-mail addresses: shariati_68@yahoo.com, C.J.Peters@tue.nl (C.J. Peters). J. Chem. Thermodynamics 59 (2013) 239–242 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct