Measurement and correlation of density and viscosity of n-alcohol–water mixtures at temperatures up to 618 K and at pressures up to 40 MPa

Abstract

Densities and viscosities of methanol-water, ethanol-water and n-propanol-water mixtures were measured over the entire range of compositions at temperatures from 523.2 to 618.2 K and at pressures up to 40 MPa. The excess molar volume calculated from the measured density changed negative to positive with increasing alcohol composition at some conditions studied, and this behavior was observed at lower temperature with increasing alkyl chain length. Maxima in composition dependence of viscosity, which is generally observed in ambient conditions, were not present at 618.2 K. Viscosities could be correlated with the Eyring's theory to within 6.4% at temperatures up to 476.2 K. The Peng-Robinson equation of state and Redlich-Kister mixing rule were used to obtain the excess Gibbs energy included in the Eyring's theory, and two binary interaction parameters in the mixing rules were determined by fitting of viscosity data. The densities were predicted using the volume translated Peng-Robinson equation of state to within 3.2% with parameters being determined by viscosity data at temperatures up to 476.2 K. A switching of fitting parameters from binary interaction parameters of the equation of state mixing rule to a proportionality constant, σ, of Eyring's theory was introduced, and viscosities and densities of the normal alcohol-water mixtures could be correlated and predicted to within 4.6% and 8.9%, respectively at temperatures above 476.2 K.