Influence of alkyl group and temperature on thermophysical properties of carboxylic acid and their binary mixtures

doi:10.1016/j.tca.2014.06.031

Thermochimica Acta

Volume 590, 20 August 2014, Pages 151-159

https://doi.org/10.1016/j.tca.2014.06.031 Get rights and content

Highlights

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Densities (ρ), sound velocities (u) and refractive index (n) were measured for carboxylic acid mixture.
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Derived properties were calculated from measured ρ, u and n, respectively.
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Redlich–Kister polynomial was used to fit the results.
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Lorentz–Lorenz equation was used to predict the density or refractive index.
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Sound velocity mixing rules were applied to the experimental sound velocity.

Abstract

In this work, volumetric, acoustic and refractive index methods have been used to study the interactions between carboxylic acids mixtures as a function of temperature and concentration. The density (ρ), sound velocity (u), refractive index (n) of butanoic acid, pentanoic acid and heptanoic acid and their binary systems (butanoic or heptanoic acid + pentanoic acid) have been measured at 293.15, 298.15, 303.15, 308.15 and 313.15 K and at p = 0.1 MPa. The Lorentz–Lorenz approximation and sound velocity mixing rules were used to test the accuracy of the experimental data. The derived properties such as excess molar volumes, $V_{m}^{E}$ , isentropic compressibilities, κ_s, excess isentropic compressibilities, $κ_{s}^{E}$ , and deviation in refractive indices, Δn, were also calculated. The Redlich–Kister polynomial equation was used to fit the excess/deviation properties. These results are useful for describing the intermolecular interactions that exist between the components in mixtures. This work also tests various sound velocity mixing rules to calculate the sound velocity of the binary mixture from pure component data, as well as examine the use of the Lorentz–Lorenz approximation to predict density from refractive index and vice versa.

Introduction

Carboxylic acids are important chemicals used in a variety of industrial applications such as separation processes, manufacture of pharmaceutical products, cleaning agents, food and beverages as an acidulant, the manufacture of polyester resins, pharmaceutical and chemical industries [1], [2], [3]. Carboxylic acids are also used as buffers, food preservatives, flavouring agents, fungicides, insecticides and catalysts [1], [2], [3], [4], [5]. A large number of natural products are either derivatives of carboxylic acids or are derived from this group of compounds. The carboxylic acid consists of two functional groups; a carbonyl group and a hydroxyl group. The hydroxyl group is bonded to a carbonyl (>C double bond O) group in the carboxyl group.

To better understand the nature of the butanoic acid, pentanoic acid and heptanoic acid and to expand on its usefulness, a detailed knowledge of the thermodynamic behaviour of these acids is essential [6], [7]. In particular, for its use as a solvent, it is important to understand the thermo physical properties: density, sound velocity, refractive index, viscosity; thermodynamic properties: heat capacity, Gibbs free energy, excess molar volume, excess molar enthalpy of the carboxylic acid and its mixtures. These properties also provide information about the intermolecular interactions [8], [9], [10], [11] and allows for the development of new correlations and/or thermodynamic predictive models. To this end, a database of the thermodynamics properties for butanoic acid, pentanoic acid and heptanoic acid can be quite useful [12], and this is the rationale for this study.

Although carboxylic acids have been widely studied, there is no data available in the literature on the properties such as density, sound velocity and refractive index for the binary systems of butanoic or heptanoic acid with pentanoic acid. This investigation is a continuation of the studies on carboxylic acid mixtures [2], [13], [14], [15], [16], [17], [18], [19], [20].

Section snippets

Chemicals

The butanoic acid (CAS No. 107-92-6) and heptanoic (CAS No. 111-14-8) acids had a purity of mass fraction ≥0.99 and was supplied by Aldrich. The pentanoic acid (CAS No. 109-52-4) had a purity of mass fraction ≥0.98 and was supplied by Merck. All the chemicals were stored over 0.4 nm molecular sieves to remove moisture. The mass percent water content was determined using a Metrohm 702 SM Titrino Metter and was found to be 0.39% in butyric acid, 0.20% in pentanoic acid, 0.26% in heptanoic acid,

Density

The thermophysical properties such as ρ, u and n were measured at 293.15, 298.15, 303.15, 308.15 and 313.15 K, and at p = 0.1 MPa for the binary systems (butanoic or heptanoic acid + pentanoic acid) and are given in Table 3, Table 4. It can be seen from these results that the ρ values decrease with an increase in temperature for both binary systems. The ρ values increase with composition for the (butanoic acid + pentanoic acid) system whereas decease for the (heptanoic acid + pentanoic acid) system.

The

Conclusions

In this work, new physico-chemical properties, which include density, sound velocity and refractive index as a function of temperature and composition, for butanoic acid, pentanoic acid and heptanoic acid and their binary mixtures, were measured. The Lorentz–Lorenz approximation predicted the refractive index from density quite accurately. Four sound velocity mixing rules were applied and these results agreed favourably; however, the most satisfactory result was obtained using the mixing rule

Acknowledgements

The authors acknowledge funding from the Department of Science and Technology (SA) and the National Research Foundation (SA) for the purchase of the DSA 5000 M and University of KwaZulu Natal for a postdoctoral scholarship for Dr I. Bahadur. This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation.

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View full text

Influence of alkyl group and temperature on thermophysical properties of carboxylic acid and their binary mixtures

Highlights

Abstract

Introduction

Section snippets

Chemicals

Density

Conclusions

Acknowledgements

Fluid Phase Equilibria

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Fluid Phase Equilibria

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Fluid Phase Equilibria

J. Chem. Thermodyn.

Amine-based systems for carboxylic acid recovery: tertiary amines and the proper choice of diluent allow extraction and recovery from water

Chemtech

Subatmospheric vapor pressure curves for propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid and heptanoic acid

J. Chem. Eng. Data

Application of reactive extraction to recovery of carboxylic acids

Biotechnol. Bioprocess Eng.

Synthesis of biodiesel via acid catalysis

Ind. Eng. Chem. Res.

Experimental determination, correlation, and prediction of physical properties of the ternary mixtures ethanoló + ówater with 1-octyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium ethylsulfate

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Theoretical studies on the hydrogen bonding interaction of complexes of formic acid with water

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