Vapor-liquid equilibria, density and sound velocity measurements of (water or methanol or ethanol + 1,3-propanediol) binary systems at different temperatures

Highlights

• VLE for water or methanol + 1,3-propanediol binary mixtures were measured.

• The investigated temperatures are 273 K–363 K.

• The NRTL, UNIQUAC and Modified UNIFAC (Do) models have been used.

• Densities and sound velocities were measured water or methanol or ethanol + 1,3-propanediol.

• The excess functions were correlated using the Redlich-Kister polynomial equation.

Abstract

In this work, vapor liquid equilibria (VLE) data for the binary systems containing {water or methanol (1) + 1,3-propanediol (2)} are reported. All measurements were performed in the temperature range of (273.15–343.15 (or 363.15)) K over the whole composition range. The experimental data were correlated using the NRTL, UNIQUAC and Modified UNIFAC (Do) models. Additionally, the experimental measurements of densities and sound velocities were measured for binary systems (water or methanol or ethanol (1) + 1,3-propanediol (2)) at atmospheric pressure and at (283.15, 293.15, 303.15 and 313.15) K. The excess/deviation functions were calculated and correlated using the Redlich-Kister polynomial equation.

Introduction

Nowadays, it is necessary to make efforts to find replacements of fossil fuels due to the diminishing of petroleum reserves and increasing of the greenhouse gas emissions. For this reason, the interest has been taken in the conversion of biomass resources into biofuels. Biodiesel is one of the promising alternative fuels to meet these problems. Biodiesel, also known as fatty acid methyl or ethyl ester, is commonly derived from the transesterification or esterification of biological feedstocks with alcohol (ethanol or methanol).From the transesterification process; glycerol is the major byproduct, approximately 10 wt.% of the total product [1], [2]. With this enormous generation of the waste stream, it is very important to explore some utilizing glycerol. One of this utilization of glycerol is the microbial conversion into1,3-propanediol (1,3-PDO) [3]. The world production of 1,3-PDO is growing rapidly due to the increasing market demand of its derivatives into highly valuable products. It is achieving over 100 million pounds per year [4]. 1,3-PDO is a colorless, odorless, viscous liquid and have properties such as non-flammable, low toxicity, miscible with water, alcohol and ethers. As a biofunctional organic molecule, 1,3-PDO has several promising properties for many synthetic reactions, such as monomer for polycondensations to produce polyesters [5]. 1,3-PDO can be also formulated into laminates, solvents, adhesives, resins, detergents, cosmetics, deodorants and other uses [6]. 1,3-PDO has a multitude of other applications as shown in Fig. 1.

1,3-PDO is mainly produced from petroleum derivatives such as ethylene oxide and acrolein through chemical processes [7]. The fermentation route to produce 1,3-PDO from a glucose feedstock is estimated to be price competitive with the petrochemical methods. The bioconversion method of glycerol into the 1,3-PDO was demonstrated using several microbial cultures such as klebsiella pneumonia [8], citrobacterfreundii [9], enterobacteragglomerans [10], clostridium butyricum [11], [12], and lactobacillus reuteri [13].

Several methods have been adopted for the separation of 1,3-PDO from the mixture containing water and alcohols. Some of these include liquid–liquid extraction [14], reactive–extractive process [15], aqueous two-phase extraction [16], and molecular distillation [17]. To carry out the recovery of 1,3-PDO, the knowledge of thermophysical properties including the density and sound velocity of water, alcohol and 1,3-PDO presents in the downstream are required. These could also provide important information on the purity of the samples as well as intermolecular interaction between the mixtures and allows developing new predictive/correlative model.

To overcome the lack of information on thermodynamic and thermophysical properties for {water or alcohol (1) + 1,3-PDO (2)} systems, the experimental data, such as vapor-liquid equilibrium, volumetric and acoustic properties for these binary systems were presented by several authors [18], [19], [20], [21], [22], [23], [24], [25], [26], [29]. Sanz et al.[18] have reported VLE data for {water (1) + 1,3-PDO (2)} at 30 kPa. Lai et al. [19] have also studied the isobaric VLE of {water (1) + 1,3-PDO (2)} at 101.3KPa and at temperature interval of (373–487) K. The vapor liquid equilibria for {water (1) + 1,3-PDO (2)} have been also investigated by Mun and Lee [20] in terms of pressure but no comparison was possible. Parsons et al. [21] have reported VLE data for {water (1) + 1,3-PDO (2)} at 25 °C. No data have been found for {methanol (1) + 1,3-PDO (2)} system. The excess molar volume for {water (1) + 1,3-PDO (2)} system were performed by Zemánková et al. [22], Czechowski et al. [26] and Checoni et al. [27] at temperatures between (283.15 and 313.15) K, The molecular interaction of alkanediols in methanol have been explained by Piekarski et al. and Orge et al. [28], [29].

In this work, VLE data for the binary systems {water or methanol (1) + 1,3-PDO (2)} are reported. All measurements were performed at atmospheric pressure and at (273.15–343.15 or 363.15) K over the whole range of composition. In addition to this, the measurements of densities and sound velocity are also presented for {water or methanol or ethanol (1) + 1,3-PDO (2)} at (283.15–313.15) K.