Experimental vapor pressures (from 1 Pa to 100 kPa) of six saturated Fatty Acid Methyl Esters (FAMEs): Methyl hexanoate, methyl octanoate, methyl decanoate, methyl dodecanoate, methyl tetradecanoate and methyl hexadecanoate

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Abstract

Vapor pressures of six saturated Fatty Acid Methyl Esters (FAMEs), methyl hexanoate (or methyl caproate), methyl octanoate (or methyl caprylate), Methyl decanoate (or methyl caprate), methyl dodecanoate (or methyl laurate), methyl tetradecanoate (or methyl myristate), and methyl hexadecanoate (or methyl palmitate) were measured from 1 Pa to 100 kPa and at temperature range between 262 and 453 K using a static apparatus. The experimental data (P-T) were compared with the available literature data.

Introduction

Fossil fuels are depleting because of the increasing demand particularly from economically emerging countries. A way to replace petrodiesel is the use of biodiesel which is mainly obtained from fatty acids (triglycerides) contained in vegetable oils (soy, corn, cotton seed oil …) or animal fats [1], [2], [3], [4]. A mixture of long chain alkyl esters is recovered through catalyst transesterification of triglycerides with alcohols such as methanol. Besides being friendly to environment (nontoxic, biodegradable and renewable fuel), biodiesel presents economic benefits because of its good combustion performance due to non-negligible presence of oxygen (10–12% by weight) which increases the combustion efficiency of the fuel [5].

Vapor pressure is an essential physicochemical property of fuels because it reflects the volatility and security of the fuel in addition to being important in the development of separation processes.

The purpose of this study is due to the lack of vapor pressures data of methyl esters as evidenced by the articles that appear constantly and which deal with the prediction of vapor pressures [6], [7], [8], [9], [10], [11], [12], [13]. As biodiesel consists predominantly of monoalkyl esters of long chain fatty acids (FAMEs), we reported vapor pressure measurements of saturated FAMEs from C6 to C16 (alkyl chain) present in the light fraction of biodiesel. The literature search revealed that only few data of Fatty Acid Methyl Esters (FAMEs) are available. From the temperature dependence of the vapor pressures, enthalpies of vaporization (ΔvapH) of the FAMEs were calculated and compared with the available literature data.

Section snippets

Chemicals

In Table 1 are reported the studied Fatty Acid Methyl Esters (FAMEs), the CAS registry number and origin as well as their purity stated by the supplier and those obtained by Gas Chromatography. The compounds were used without further purification.

Apparatus

Vapor pressures were measured using a static apparatus [14]. A short description with the main points is given below and represented in Fig. 1. Prior to the loading of the compound into the cell, the apparatus is heated at 200 °C and submitted to high

Results and discussion

The experimental T and P values of the different FAMEs are reported in Table 2. The data were fitted using the Antoine equation:log10P/Pa=A-BC+T/K

A, B, and C are the Antoine Equation Constants reported in Table 3. The minimized objective function Q is as follows:Q=∑Pcalc-PexpPexp2

In Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 are plotted the relative vapor pressure deviation between the literature data and those obtained in the present study. For methyl hexanoate, Fig. 2, our values are in

Conclusion

In this work, we presented vapor pressures of six FAMEs in a large pressure range (from 1 Pa to 100 kPa) determined by a static apparatus. The obtained results are consistent and in good agreement with different authors’ data available in literature, the mean relative deviation do not often exceed 5%. From the experimental T-P values, the calculated enthalpies of vaporization ΔvapH (298.15 K) are also in a good agreement with the experimental enthalpy of the literature which confirm the

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