Modelling the solid-liquid-vapour phase behaviour of n-alkanes in a TPT-1 framework
File(s)
Accepted version
Author(s)
Ramirez-Carpio, Viridiana
Galindo, Amparo
Gil-Villegas, Alejandro
Type
Journal Article
Abstract
We study the global phase behaviour of n-alkanes applying Wertheim's first order thermodynamic perturbation theory (TPT1). The molecules are modelled as homonuclear chains comprised of m freely jointed spherical segments interacting via the Lennard-Jones potential. Vega et al. [J. Chem. Phys. 116, 17 (2002)] have shown that the TPT1 is suitable to treat solid phases as well as fluid phases when model chains are considered, but that the adoption of a fully flexible chain model leads to the under-prediction of triple point temperatures and overestimation of the fluid ranges in comparison to experiment. Here, we propose a model in which a different number of segments are used to treat the fluid and the solid phase. The number of segments used to model the molecules in the fluid phase 𝑚f, and the LJ monomer potential parameters σ and ε are taken from published soft-SAFT values, whereas in the case of the solid phase a reduced temperature-dependent effective chain length 𝑚s(𝑇∗) is determined through a minimisation between theoretical and experimental liquid-solid phase equilibrium data. We refer to this model as effective-solid TPT1 (es-TPT1). We use the model proposed to calculate the solid–liquid–vapour phase diagrams of several n-alkanes and compare with experimental data. In the approach proposed, the conformation of chains in the solid phase is decoupled from the fluid phase, and an excellent description of the melting properties, as well as accurate predictions of the triple point temperatures for the n-alkanes examined is obtained. This simple solution provides an avenue to model the solid–liquid–vapour phase behaviour of other real substances in a TPT1 framework, and hence within the SAFT family of equations.
Date Issued
2023-11-21
Date Acceptance
2023-04-13
Citation
Molecular Physics, 2023, 121 (19-20)
ISSN
0026-8976
Publisher
Taylor and Francis Group
Journal / Book Title
Molecular Physics
Volume
121
Issue
19-20
Copyright Statement
Copyright © 2023 Taylor & Francis. This is an Accepted Manuscript of an article published by Taylor & Francis in Molecular Physics on 27 Apr 2023, available at: https://doi.org/10.1080/00268976.2023.2204150
Identifier
https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000979932700001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=a2bf6146997ec60c407a63945d4e92bb
Subjects
ASSOCIATING FLUID THEORY
CHAIN MOLECULES
Chemistry
Chemistry, Physical
DIFFERENTIAL THERMAL-ANALYSIS
DIRECTIONAL ATTRACTIVE FORCES
EQUATION-OF-STATE
HIGH-PRESSURE
MOLECULAR-DYNAMICS
n-alkanes
phase behaviour
Physical Sciences
Physics
Physics, Atomic, Molecular & Chemical
SAFT EQUATION
Science & Technology
solid-liquid equilibrium
SURFACE-TENSION
THERMODYNAMIC PERTURBATION-THEORY
TPT1
Publication Status
Published
Article Number
e2204150
Date Publish Online
2023-04-27