High pressure phase equilibria of the ternary system l-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide + carbon dioxide + ferrocene

摘要

The phase behavior of the ternary system consisting of the organometallic compound ferrocene+the ionic liquid 1 -butyl-3-methylimidazolium bis(trifiuoromethylsulfonyl)imide ([bmim][Tf2N]) + supercritical carbon dioxide (CO2) is determined experimentally using the Cailletet apparatus. Ferrocene is a building block for wide range of applications from homogeneous catalysis and material science to biology and medicine, and is solid up to 445 K. Experimental data for all phase transitions (solid + liquid + vapor→ solid + liquid, solid + liquid → liquid, liquid + vapor → liquid) within a temperature range of 278.38-368.47 K, a pressure range of 0.694-9.24 MPa and a CO2 concentration range of 10-50 mol% are collected, while the ratio of [bmim][Tf2N] versus ferrocene is kept constant. It is shown that CO2 acts as a co-solvent in all measurements, even at high CO2 concentrations (50mol%). Ferrocene is thus more soluble in the [bmim][Tf2N] + CO2 mixture than in pure [bmim][Tf2N]. Removing CO2 from the system by pressure release results in precipitation of the ferrocene, so that it can be recovered from the ionic liquid phase. This is contrary to many other IL+organic systems that show anti-solvency behavior in the presence of large amounts of CO2, where it is possible to recover the organic compound as precipitate by the addition of supercritical CO2. The results stress the importance of the availability of phase behavior data for the design of new chemical processes.