Furthermore, 𝛾 𝑖 ,υ 𝑖 , refers to the coefficient of activity/volume of the pure liquids/second virial coefficients, respectively. The coefficients of activity are described by the NRTL model, subsequently, the parameters are tabulated in Table . In Table Consequently, the left side of equation ( ) must be constrained to the value of the working pressure during the operation. The pressure-swing process scheme presented in Figure , assumes "one-pass" through the column at the time [2], in the other words it is assumed that columns work consecutively ("twostep" process). In step (1) LP run (rectifier), and, in step ( ), HP run (stripper), whereas the maximum achievable distillate concentration at lower pressure 𝑃 1 = 1atm is 78% of acetone, but, at In the same Figure , the vapor-liquid equilibrium is presented for a mixture of acetonemethanol at different pressures: the data obtained from MATLAB simulation are plotted against CHEMCAD professional simulator for the same thermodynamics model, described previously. In Figure , on the right/left side plot, resp., the vapor-liquid equilibria for pressure set at 𝑃 1 = 1atm/𝑃 2 = 10atm, resp., shows that the azeotropic point coincides with 78%/37%, resp., contain of acetone in the mixture.