High-pressure phase behavior Of CO2/acetone/1-n-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF6]) system was studied by the analytical method at 313.15 K and at pressures up to 15 MPa. The ternary system forms two phases at most conditions. At pressures from 4.9 to 8.1 MPa. a three-phase region appeared in the system. Pressure influenced the slopes of the tie lines in the two-phase region greatly. On the basis of phase equilibrium data, the distribution coefficients of the components between different phases were calculated. CO2 distribution coefficient decreased with increasing pressure while acetone distribution coefficient increased with pressure. (C) 2006 Elsevier B.V. All rights reserved.