The high pressure phase behavior of a binary mixture containing hydrogen (H-2) 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-dimethyl-phospholano)benzene (cyclooctadiene)rhodium(I) tetrafluoroborate (Rh-MeDuPHOS) on H-2 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 H-2 solubility in [bmim][BF4] compared to those of binary mixtures of H-2 + [bmim][BF4] throughout the whole temperature range studied. However, the addition of CO2 to the binary system of H-2 + [bmim][BF4] increases the H-2 solubility at lower temperatures (<330 K), and decreases it at higher temperatures (> 340 K). (c) 2013 Published by Elsevier Ltd.