MOLECULAR SHAPE EFFECTS ON LIMITING ACTIVITY-COEFFICIENTS - NORMAL, BRANCHED AND CYCLIC ALKANES IN 1-PROPANOL OR 2-PROPANOL

The limiting activity coefficients were determined by the inert gas st ripping method or the modified Rayleigh distillation method at 308.15 K for four linear alkanes (C-5-C-8), three branched alkanes (C-6-C-8), and three cycloalkanes (C-5-C-7) in l-propanol and in 2-propanol. The data were determined with very good precision (1-2%) and indicate tha t isomerization and molecular shape have an important effect over gamm a(1)(infinity) values. Comparison against calculations using two versi ons of the UNIFAC model illustrates that the so-called first-order gro ups do not contain all the important molecular structure information. Hence, the experimental data reported here should be useful to improve models based on group contributions to describe the phase equilibria of the present mixtures. (C) 1997 Elsevier Science B.V.