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ARTICLE
pubs.acs.org/jced

Activity Coefficients at Infinite Dilution for Hydrocarbons in Fatty
Alcohols Determined by Gas-Liquid Chromatography
Mehdia Boussaha,†,‡ Kamel Khimeche,§ and Abdellah Dahmani*,†
†

Laboratory of Thermodynamics and Molecular Modeling, Faculty of Chemistry, USTHB, Bab Ezzouar, BP 32 El-Alia,
16111 Algiers, Algeria
‡
University Center of Khemis-Miliana, TheniatElhad Road, 44225, Soufay, Khemis-Miliana, Ain-Defla, Algeria
§
UER of Applied Chemistry, Polytechnic Military School, EMP, BP 17 Bordj El-Bahri, Algiers, Algeria
ABSTRACT: The selection of the most suitable selective solvent for separation processes such as extraction or extractive distillation
plays an important role in the economical design. Since the largest deviation from ideality isobserved at infinite dilution, limiting
activity coefficients (γ¥) provide a useful tool for the optimal choice of the selective solvent. Therefore, activity coefficients at infinite
dilution have been measured for 22 solutes (paraffins, olefins, chloroparaffins, aromatics, ketones, ethers, alcohols, and acetates) in
fatty alcohols: octadecanol and eicosanol as a solvent. The measurements were carried outwith the help of gas-liquid
chromatography (GLC) at five and four temperatures, respectively. Furthermore, the observed temperature dependence of
limiting activity coefficients is confirmed using excess enthalpy data. To determine the different interactions between the solutes and
the solvents, the linear solvation energy relationship (LSER) or “Abraham method” is applied. To verify the application asan
entrainer, the selectivity and capacity of the investigated solvents are calculated from experimental activity coefficient data.

’ INTRODUCTION
Infinite dilution activity coefficients characterize the behavior
of a single solute molecule completely surrounded by solvent;
thus, it generally indicates a maximum nonideality and provides
incisive information regarding solute-solvent interactionsin the
absence of solute-solute interactions,1 and it is actually an excess
property. Also, it is much simpler to describe or model by using
statistical mechanical theories or computer simulation methods,2
and thus, activity coefficients provide helpful information for
testing the possible applicability of a theoretical model or a
simulation method.3
From the industrial viewpoint, infinitedilution activity coefficient theory offers a wider applicability than any measurement at
finite concentration, and it can be used to predict the phase
behavior of a mixture over the entire concentration range.4
A reliable knowledge of the activity coefficients at infinite
dilution (γ¥i) is of particular importance for the synthesis,
design, and optimization of separation processes, since the
largestseparation effort is required to remove the last traces of
impurities. Furthermore, γ¥i values are required to select selective solvents (entrainers) for separation processes such as
extractive distillation and extraction or to check for separation
problems (azeotropic points, miscibility gaps). Additionally,
more reliable gE model or group interaction parameters are
obtained by fitting therequired parameters simultaneously to
vapor-liquid equilibria (VLE), excess enthalpies (HE), and
limiting activity coefficients (γ¥i).
Activity coefficients at infinite dilution can be determined by
various methods: ebulliometry, static methods, the dilutor technique, and gas-liquid chromatography (GLC).5 The GLC technique was chosen as the most preferable measurement technique
for the plannedinvestigation because GLC shows several advantages in comparison to other methods: static methods, dilutor
r 2010 American Chemical Society

technique, and so forth.6 After the careful preparation of the
column, the GLC method allows the measurement of a great
number of γ¥ values in a rather short time. The reliability of the
γ¥ data obtained by GLC has been confirmed by different
authors7 and...