Experimental measurement of carbon dioxide solubility in 1-methylpyrrolidin-2-one (NMP) + 1-butyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate ([bmim][BF4]) mixtures using a new static-synthetic cell

A new experimental setup based on the “static-synthetic” method was designed and commissioned for the measurement of solubility from vacuum to moderates pressures. The new apparatus and experimental method were extensively validated by measuring the solubility of carbon dioxide in three pure solvents, viz., n-hexane, n-methyl-2-pyrrolidone and 1-butyl-3-methylimidazolium tetrafluoroborate. New solubility data for carbon dioxide in hybrid solvents with different mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate + n-methyl-2-pyrrolidone were measured at three temperatures, viz. (298.15, 313.15 and 323.15) K. Additionally, viscosity, density and sound velocity for binary mixtures of n-methyl-2-pyrrolidone + 1-butyl-3-methylimidazolium tetrafluoroborate were measured. The experimental phase equilibrium data were modelled using the Peng-Robinson equation of state and van der Waals mixing rule. In general, the solubility of carbon dioxide in the hybrid solvent was lower than the respective pure constituents. However, the hybrid solvent exhibited a significantly lower viscosity than the pure ionic liquid.