A liquid phase viscosity–temperature model for long-chain n-alkanes up to C64H130 based on the Free Volume Theory

• Free Volume Theory is applied to long chain alkanes.
• Pure component long-chain n-alkane viscosities, up to C64H130, modelled as a function of density and temperature.
• Pressure and temperature ranges 0.1–142 MPa and 273.15–573.15 K.
• Models provided to estimate molecular characteristics as a function of molecular weight.

The viscosity, as a function of density and temperature, of long chain normal alkanes (n-alkanes) in the liquid phase, is modelled using the Free Volume model, as presented by Allal, Moha-Ouchane and Boned in 2001. Free Volume molecular characteristics as a function of molecular weight are calculated at discrete points, using a least-squares method to fit the model to measured data available from literature. The results are used as control points in developing polynomials to extrapolate the characteristic parameters to all n-alkanes up to C64H130. Results obtained with the Free Volume model for long-chain n-alkanes are compared to those obtained from other models and methods, such as the Hard Sphere model, the Lohrenz–Bray–Clark correlation, and Pedersen’s corresponding states method. The Extended Free Volume model resulted in an average absolute deviation of 5.3% for n-alkanes with carbon numbers C6–C64, over pressure ranges up to 142 MPa (1400 bar) and temperatures up to 573.15 K (300 °C).