Viscosity modeling of propyl butanoate and 2-alkanol mixtures using modified Cohen-Turnbull and UNIFAC-VISCO approaches.

Authors

Mohammad Almasi, Adel Noubigh

Published in

Scientific reports. Jul 12, 2026. Epub Jul 12, 2026.

Abstract

Densities and dynamic viscosities of binary mixtures containing propyl butanoate (PB) with 2-propanol, 2-butanol, 2-pentanol, 2-hexanol, and 2-heptanol were measured at temperatures ranging from 293.15 K to 323.15 K and ambient pressure. Two distinct modeling approaches were developed and rigorously evaluated against the experimental data: the Modified Extended Cohen-Turnbull Model (M-ECTM) and the Excess Free Volume Corrected UNIFAC-VISCO (EFVC-UNIFAC) model. While the standard UNIFAC-VISCO group-contribution method exhibited substantial systematic deviations (global AARD = 8.0%, bias = - 6.8%) due to its inability to capture hydrogen-bonding disruption and volume expansion effects, both proposed models achieved significant improvements. The M-ECTM, incorporating composition-dependent activation barriers via Redlich-Kister expansion, yielded the highest overall accuracy with a global AARD of 2.9% and MaxAD of 5.8%, utilizing three adjustable parameters per binary system. Conversely, the EFVC-UNIFAC approach, which introduces a single corrective term proportional to the experimental excess molar volume (V^E), achieved comparable precision (global AARD = 3.1%, MaxAD = 7.2%) with only one binary parameter (ξ₁₂). This parameter exhibited an increasing trend with increasing alcohol chain length (0.048 for 2-propanol to 0.084 for 2-hepatanol). Both models effectively eliminated systematic bias (|bias| < 0.5%), with the M-ECTM performing marginally better for longer-chain alcohols and the EFVC-UNIFAC demonstrating superior statistical efficiency. These results establish that the M-ECTM is optimal for maximum precision, whereas the EFVC-UNIFAC offers an excellent compromise between accuracy and parsimony for engineering applications involving ester-alcohol mixtures.

PMID:
42437789
Bibliographic data and abstract were imported from PubMed on 13 Jul 2026.

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