Group contribution equation of state based on the lattice fluid theory: Alkane–alkanol systems

A new group-contribution equation of state (EOS) is proposed and applied to phase equilibrium calculations. The EOS is based on the generalized van der Waals theory and combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression. The EOS is applied to vapor–liquid equilibrium (VLE) calculations in systems containing pure hydrocarbons, alcohols, and their binary mixtures. These systems cover a wide range of situations, including nonpolar and polar compounds of different sizes and mixtures ranging from nearly-ideal to azeotropic behavior. Using VLE data for pure substances and binary mixtures of linear hydrocarbons, the parameters of linear alkane groups (CH3 and CH2) were simultaneously fitted. For pure linear alkanes up to C12, calculated vapor pressures deviate less than 1.7% from the experimental values. Predicted vapor pressures of eight heavy hydrocarbons (from C14 to C28) are in satisfactory agreement with experimental data. The parameters for other groups (branched alkanes and alcohol groups) were fitted sequentially, using data for pure compounds and binary mixtures only containing the characteristic group being estimated and linear alkane groups. Satisfactory predictions of the vapor pressures of pure substances and bubble pressures of binary mixtures were obtained.