Viscosity Modeling of Pure Alcohols Based on the Significant Structure Theory and a Cubic Equation of State

Abstract

In this study, a previously developed model [Macías-Salinas, R.; Viscosity Modelling of Reservoir Fluids over Wide Temperature and Pressure Ranges. Chem. Eng. Trans. 2013, 32, 1573.] based on the significant structure theory (SST) in conjunction with the Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) cubic equations of state (CEoS) was modified for the accurate correlation of the viscosity of 25 pure alcohols from methanol to n-dodecanol, branched alcohols, diols, and triols at temperatures from 0 to 272 °C and pressures from 0.98 to 4860 bar, obtaining two final model versions (SST-SRK and SST-PR) valid for both gas and liquid phases in the case of methanol, ethanol, 2-propanol, and 2-methyl-1-propanol and only in liquid phase for the rest of alcohols considered here. In regard to n-decanol, n-undecanol, n-dodecanol, 1,3-propanediol, and 1,4-butanediol, they were studied at different temperatures but only at a pressure of 1 bar. The resulting model versions were correlated with 2418 dynamic viscosity experimental data, obtaining overall values of average absolute deviation (AAD), statistical bias, and absolute maximum deviation (AMD) of 1.4808, 0.0503, and 7.9217%, respectively, with the SST-SRK approach and 1.4799, 0.0476, and 7.4515%, respectively, with the SST-PR approach. The two modeling approaches were compared with the friction theory [Zéberg-Mikkelsen, C. K.; Viscosity Modeling of Associating Fluids Based on the Friction Theory: Pure Alcohols. Fluid Phase Equilib. 2002, 194–197, 1191.] (FT) and free volume theory [Allal, A.; A New Free Volume Model for Dynamic Viscosity and Density of Dense Fluids Versus Pressure and Temperature. Phys. Chem. Liq. 2001, 39, 1.] (FVT), using the same experimental viscosity database of this work under the same conditions of temperature and pressure, obtaining more accurate results with the SST approach for most of the modeled alcohols.