Solid–liquid phase equilibrium and dissolution properties of ethyl vanillin in pure solvents

doi:10.1016/j.jct.2016.10.029

The Journal of Chemical Thermodynamics

Volume 105, February 2017, Pages 345-351

https://doi.org/10.1016/j.jct.2016.10.029 Get rights and content

Highlights

•
Solubility of ethyl vanillin in eight pure solvents were determined by a static analytical method.
•
The experimental solubility data of ethyl vanillin were correlated and analyzed by four thermodynamic models.
•
Dissolution thermodynamic properties of ethyl vanillin were calculated and discussed.

Abstract

The solubility of ethyl vanillin (EVA) in eight pure solvents were determined in different temperature ranges from (273.15 to 318.15) K by a static analytical method. In the temperature ranges investigated, it was found that the solubility of EVA in all the selected solvents increased with the rising of temperature. Furthermore, four thermodynamic models were used to correlate the experimental solubility data and the calculation results showed that selected models can be used to correlate the solubility data with satisfactory accuracy. Finally, the dissolution thermodynamic properties, including dissolution Gibbs energy, dissolution enthalpy and dissolution entropy of EVA in the eight selected solvents were calculated.

Introduction

As one of the important separation and purification methods, solution crystallization are widely used to make many kinds of products, such as pharmaceuticals, fine chemicals, spices and so on. The design and operation of crystallization processes will directly affect the quality of the final product, such as purity, yield, and crystal characteristics. The physiochemical properties, including solubility and dissolution thermodynamics, are the foundation of crystallization process. Compared with other process parameters, solubility of solute in different solvents will determine the selection of crystallization method and the optimization of crystallization process [1], [2], [3]. Therefore, it is crucial to know the accurate equilibrium solubility data of target product in different solvents.

Ethyl vanillin (EVA, CAS Registry NO. 121-32-4), 3-ethoxy-4-hydroxybenzaldehyde (C₉H₁₀O₃, as shown in Fig. 1), is one kind of white or pale yellow acicular crystal. It has been widely used as the flavor additives in the foods, perfumes and commodity industries, and also as the medical intermediates for the pharmaceutical industry [4]. As one of the most valuable synthetic perfumes, EVA has gradually become a substitute for vanillin [5]. It sends out a strong chocolate flavor and the aroma is approximately 3.5 times as rich as the same amount of vanillin, which can reduce the cost and enhance economic efficiency of industrial production [6], [7], [8]. In the production of EVA, crystallization process is one of the important unit operation which will directly determine the quality of the final product. The thermodynamic data of EVA, such as solubility and dissolution enthalpy, is important for the designing and optimizing of the crystallization process of EVA. However, little information on the thermodynamic data of EVA can be found from literature.

In this work, the solubility data of EVA in different pure solvents (including methanol, ethanol, n-propanol, i-propanol, acetonitrile, acetone, methyl acetate and ethyl acetate) were obtained from 273.15 K to 318.15 K by the synthetic method [9], [10]. The Apelblat equation, the λh equation and two local composition models (Wilson and NRTL model) were chosen to correlate and analyze the experimental solubility data of EVA. In addition, to understand the dissolution behavior of EVA in the selected solvents, dissolution thermodynamic properties, such as the dissolution Gibbs energy, dissolution enthalpy and dissolution entropy, were calculated and discussed, basing on the experimental solubility data and the Wilson model.

Section snippets

Materials

Ethyl vanillin (EVA) with purity (mass fraction) of 0.990, supplied by Aladdin Industrial Corporation, Shanghai, China, was used without further purification. All of the organic solvents used in this study, including methanol, ethanol, n-propanol, i-propanol, acetonitrile, acetone, methyl acetate and ethyl acetate, were purchased from Tianjin Jiangtian Chemical Co. of China with mass fraction purity higher than 0.995. The details, including source and purity of all the materials used in this

The modified Apelblat equation

The modified Apelblat equation is a widely used semi-empirical equation which was deduced from the Clausius-Clapeyron equation. It can be used to correlate the solid-liquid equilibrium and the equation is shown as following [15], [16]. $\ln x_{1} = A + \frac{B}{T} + C \ln T$ where x₁ is the mole fraction solubility of solute, T refers to the absolute temperature. A, B and C are empirical parameters. A and B refer to variation of activity coefficient in real solution, and C represents the effect of temperature on the

The characterization of samples

The PXRD pattern of all the EVA samples were found to be the same, which is given in Fig. 2. It confirmed that all the samples of EVA used in this study are the same crystalline form with high crystallinity, and the EVA have characteristic peaks at 2θ of 12.10°, 20.94°, 22.54°, 26.24° and 37.22°.

The DSC analysis results of EVA used in this study are shown in Fig. 3. It can be seen from the DSC data that the melting temperature (352.98 K) is in agreement with the literature value T_m = 350.15–352.15

Conclusions

In this study, the solubility of EVA in eight pure solvents were measured at the temperatures ranging from 273.15 K to 318.15 K by using a static analytical method. The solubility data of EVA in all selected solvents increase with the increasing of temperature. Furthermore, the experimental solubility data were correlated and analyzed by four thermodynamic models. The correlated values are in good agreement with the experimental values throughout the entire range of temperature tested. Finally,

Conflict of interest

The authors declare no competing financial interest.

Acknowledgments

The authors are very grateful to the financial supported from National Natural Science Foundation of China (No. 51478308) and Major National Scientific Instrument Development Project (No. 21527812).

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Solid–liquid phase equilibrium and dissolution properties of ethyl vanillin in pure solvents

Highlights

Abstract

Introduction

Section snippets

Materials

The modified Apelblat equation

The characterization of samples

Conclusions

Conflict of interest

Acknowledgments

Food Chem.

J. Chem. Thermodyn.

Fluid Phase Equilib.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

J. Chem. Thermodyn.

Fluid Phase Equilib.

Fluid Phase Equilib.

J. Pharm. Sci.

Crystallization

Crystallization Technology Handbook

J. Pharm. Pharm. Sci.

Arch. Pharmacal Res.

Am. Lab.