Vapor‐liquid equilibrium of polymer solutions using a cubic equation of state

Abstract

A recently proposed mixing rule has been combined with a cubic equation of state to correlate the vapor-liquid equilibria of various polymer + solvent and solvent + long chain hydrocarbon mixtures. We find that the two-parameter version of this model can correlate the solvent partial pressure in concentratedpolymer solutions with high accuracy over a range of temperatures and pressures with temperatureindependent parameters. For the solvent + long chain hydrocarbon systems, for which accurate vapor-phase concentrations are also important, the model is best used as a three-parameter correlation. Advantages of this approach are that it extends the application of cubic equations of state to polymer + solvent systems in a simple fashion and that generally only temperature-independent parameters are required which allow for accurate interpolation and extrapolation of available data.

A Survey of Equations of State for Polymers

“…This leads to small contributions of the new added parameters and terms that are strongly composition dependent. Consequently, as the number of components increases, the mixing rule is effectively reduced to a quadratic dependence, as in the one-fluid van der Waals fluid theory [38].…”

“…Therefore, it is possible to use zero-pressure experimental densities to determine them. Alternatively, the approach adopted by Orbey and Sandler [38] may be employed, i.e. to use densities at low pressure with a hypothetical and very low vapor pressure, for example 10 -7 MPa.…”

Prediction of Vapor-Liquid Equilibria Using Peng-Robinson and Soave-Redlich-Kwong Equations of State

“…Despite its simplicity, the Flory±Huggins model is still an industry standard with abundant information available about the Flory±Huggins parameter (w) for polymer±solvent mixtures [184,185]. Orbey and Sandler [179] pointed out one important aspect of using the FH model. They opined that, since the FH model was developed using a rigid incompressible lattice, a PVT equation of state can not be derived from it.…”

“…If the molecular weight of a polymer or a long±chain hydrocarbon is relatively low, then an appreciable amount of it will be present in the vapor phase and this may be important in the dewaxer design. Several other processes require a quantitative description of the VLE of polymer±solvent systems [179].…”

Modification of Sako-Wu-Prausnitz equation of state for fluid phase equilibria in polyethylene-ethylene systems at high pressures

“…In a series of papers, this approach was applied with satisfactory results to: (1) the correlation and prediction of VLE , Harismiadis et al, 1994a; (2) the correlation and prediction of LLE in polymer solutions and blends (Harismiadis et al, 1994b, Saraiva et al, 1996; and (3) the correlation and prediction of Henry constants (Bithas et al, 1996). (Orbey and Sandler, 1994), fitted the two parameters of the PRSV equation of state for the pure polymer to its volumetric data at the temperature range of interest by assuming that its vapor pressures equal to 10 -7 MPa. In order to correlate the VLE in polymer solutions, they employed the mixing rule proposed by (Wong and Sandler, 1992) by coupling the equation of state FH G E model, and employing two binary interaction parameters, ij k and χ (Flory interaction parameter).…”