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
The high pressure phase behavior of a binary mixture containing hydrogen (H2) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) 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][BF4] as the reaction medium, the effects of adding carbon dioxide (CO2) or the hydrogenation catalyst (−)-1,2-bis((2R,5R)-2,5-dimethylphospholano)benzene (cyclooctadiene)rhodium(I) tetrafluoroborate (Rh-MeDuPHOS) on H2 solubility in [bmim][BF4] 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 H2 solubility in [bmim][BF4] compared to those of binary mixtures of H2 + [bmim][BF4] throughout the whole temperature range studied. However, the addition of CO2 to the binary system of H2 + [bmim][BF4] increases the H2 solubility at lower temperatures (<330 K), and decreases it at higher temperatures (>340 K). âº The presence of catalyst decreased the bubble point pressures. âº The addition of CO2 decreased the bubble point pressure at lower temperatures. âº The addition of CO2 increased the bubble point pressure at higher temperatures. âº [bmim][BF4] is a viable option as the hydrogenation solvent.