A Simple and Practical Theoretical Model for Interpreting Binary Azeotropes

07 December 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We put forth a simple and yet practical theoretical model generalized from Raoult’s law and Henry’s law and show that it can be reduced to these two laws under limiting conditions. The model entertains a hybrid parameter h_B with activity coefficient bundled into it, which smoothly bridges the p_B^* and K_B coefficients in Raoult’s law and Henry’s law. The value of h_B falls in the interval of [K_B, p_B^*] or [p_B^*, K_B] in the case of negative or positive deviation from Raoult’s law, respectively. We uncover an overlapping rule for the ranges of h_A and h_B, which binary mixtures must obey to form azeotropes. We also provide straightforward ways to analyze the characteristic mole fraction and pressure for azeotropes and to understand the relative positions of vapor composition curves with respect to the liquid counterparts. We rely heavily on experimental data available in the literature for representative binary mixtures with both negative and positive deviations from Raoult’s law to illustrate the algebraic derivations. The knowledge gained is useful in the analysis of experimental data from vaporliquid equilibrium measurements and possess pedagogical merit in various relevant fields.

Keywords

Azeotrope
Raoult's law
Henry's law
vapor-liquid equilibrium
theoretical modeling

Supplementary materials

Title
Description
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Title
Azeotrope_SM1_LB5412
Description
Supplementary Material showing all the detailed steps for data analysis using the experimental data of binary dimethoxymethane−carbon disulfide solution {𝑥𝐴C3H8O2 + 𝑥𝐵CS2} at 308.32 K taken from literature.
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