Solubility determination and thermodynamic modelling of terephthaldialdehyde in ten organic solvents from T = (273.15 to 318.15) K and mixing properties of solutions

Highlights

• Solubility of terephthaldialdehyde in ten solvents were determined.

• The fusion enthalpy of terephthaldialdehyde were determined.

• The solubility were correlated with four thermodynamic models.

• The mixing properties of solutions were evaluated.

Abstract

Knowledge of solubility for terephthaldialdehyde in different solvents is essential for its purification and further theoretical investigations. In this work, the solubility of terephthaldialdehyde in ten solvents of ethanol, n-propanol, 1-butanol, isopropanol, benzyl alcohol, 2-butanone, acetonitrile, isopentanol, N,N-dimethylformamide, and acetone were determined by an isothermal saturation method at temperatures ranging from (273.15 to 318.15) K under atmospheric pressure. By and large, the solubility of terephthaldialdehyde decrease according to the following order in different solvents: N,N-dimethylformamide > benzyl alcohol > 2-butanone > acetone > acetonitrile > isopentanol > 1-butanol > n-propanol > ethanol > isopropanol. In addition, values of the measured solubility were correlated with the Buchowski–Książczak λh equation, modified Apelblat equation, Wilson model and NRTL model. The largest values of relative average deviation and root-mean-square deviation were 1.2% and 8.7 × 10⁻⁴, respectively. The correlated values with the four models agreed well with the experimental values and the Apelblat equation model provided better correlation results than the other three models. Furthermore, the mixing properties, including mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (${\gamma }_1^{\infty }$) and reduced excess enthalpy ($H_1^{\text{E,}\infty }$) were computed. The solution process of terephthaldialdehyde was spontaneous and favourable in these solvents. Knowledge of the solubility and thermodynamic investigations would be very important for optimizing the purification process of terephthaldialdehyde.

Introduction

Aromatic aldehydes have aldehyde groups with a high reactivity, so they may be employed in a wide variety of uses. Particularly, terephthalaldehyde (CAS No. 623-27-8) having two aldehyde groups at para-positions is gaining focus as basic material of medicinal products [1], agrichemicals [2], pigments [3], liquid crystal polymers [4], electro-conductive polymers [5], and heat-resistant plastics [6]. In the previous publications, many methods have been proposed to prepare terephthaldialdehyde. In the methods for preparing terephthalaldehyde, there is a method for dehydrating intermediates obtained via chlorination [7], [8], a method for hydrogenating methylterephthalate [9], [10], or a method for preparing terephthalate by oxidising p-xylene in vapour phase [11], [12], etc. However the resulting reaction mixture contains some impurities in terephthalaldehyde, such as benzaldehyde, p-tolualdehyde, 4-hydroxybenzaldehyde and the like. In order to use terephthalaldehyde as a raw material in a polymer synthesis or a fine chemical process, it should be purified to a high purity by efficiently removing the impurities produced in the synthesis of terephthalaldehyde.

Several methods have been reported to obtain terephthaldialdehyde with a high purity [13], [14], [15], [16], [17], [18], [19], [20], [21] which may be used in the polymer synthesis or the fine chemical process. The crude product of terephthaldialdehyde can be purified via a method of solvent extracting-drying-subliming [13]. However this method has problems that its procedures are complicated and a non-environment friendly compound, chloroform, is used as a solvent. Recently, the solvent crystallization process has been developed to purify the crude terephthaldialdehyde [14], [15], [16], [17], [18], [19], [20], [21]. During the purification process of terephthaldialdehyde by using solvent crystallization, the solubility has direct effects on the purity and quality of the final product. Therefore, the solubility of terephthaldialdehyde in different solvents and dissolution thermodynamic properties are very important in the optimization process of crystallization. Nevertheless, it is unfortunate that many studies have been focused on the production of terephthaldialdehyde, virtually work has been carried out to obtain physicochemical information on its solubility in solvents up to the present.

The main objectives of this work are to (1) measure the fusion enthalpy of terephthaldialdehyde under atmosphere pressure; (2) determine the solubility of terephthaldialdehyde in different organic solvents at temperatures ranging from (273.15 to 318.15) K by the method of high-performance liquid phase chromatograph; (3) correlate the solubility using different thermodynamic models; and (4) calculate the mixing thermodynamic properties for the dissolution process of terephthaldialdehyde in different solvents.