Henry’s law constants and infinite dilution activity coefficients of propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene in 1-pentanol, 2-pentanol, and 3-pentanol

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Abstract

Henry’s law constants and infinite dilution activity coefficients of propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene in 1-pentanol, 2-pentanol in the temperature range of (250 to 330) K and 3-pentanol in the temperature range of (260 to 330) K were measured by a gas stripping method. A rigorous formula for evaluating the Henry’s law constants from the gas stripping measurements was used for the data reduction of these highly volatile mixtures. The uncertainty is about 2% for the Henry’s law constants and 3% for the estimated infinite dilution activity coefficients. In the evaluation of the infinite dilution activity coefficients, the nonideality of the solute such as the fugacity coefficient and Pointing correction factor cannot be neglected, especially at higher temperatures. The estimated uncertainty of the infinite dilution activity coefficients includes 1% for nonideality.

Introduction

A systematic study of gas solubilities including the Henry’s law constant is useful in providing design data for absorption processes as well as indirectly in aiding the analysis of molecular interactions in solutions.

Although a large number of (alkane + alcohol) and (alkene + alcohol) solubility data have been published, few data are available for C4 gases such as butane, 1-butene, and their isomers. The solubility data will be useful in developing prediction methods. Especially for group contribution methods, it may be necessary to take into account the differences between isomers.

To estimate the gas solubility from a molecular theory or molecular simulation, on the other hand, an accurate intermolecular potential is necessary. The Henry’s law constant is directly related to the residual chemical potential of the solute at infinite dilution, which is evaluated from the intermolecular potential between a solute molecule and a solvent molecule. Therefore, the Henry’s law constant is a suitable macroscopic property for testing the intermolecular potential between different kinds of molecules.

The gas stripping method, proposed by Leroi et al. [1], has been used to measure the activity coefficients at infinite dilution of liquid solutes in nonvolatile solvents. In previous work [2], [3], [4], [5], [6], the Henry’s law constants for propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene in methanol, propanols and butanols were measured with this method. For these highly volatile solutes and solvents, a rigorous expression had been derived for data reduction [2].

In this work, the Henry’s law constants for propane, propene, butane, isobutane, 1-butene, isobutene, trans-2-butene, and 1,3-butadiene in 1-pentanol, 2-pentanol, and 3-pentanol are measured by the gas stripping method, and the infinite dilution activity coefficients of solutes are evaluated.

Section snippets

Theory

The gas stripping method, originally proposed by Leroi et al. [1], is based on the variation of the vapor-phase composition when the highly diluted solute in a liquid mixture in an equilibrium cell is stripped from the solution by the flow of inert gas (helium). The composition of the gas leaving the cell is periodically sampled and analyzed by gas chromatography (g.c.). The g.c. signal area, S, of the solute decreases exponentially with the volume of inert gas flowing out of the cell by the

Experimental

Details of the experimental apparatus were presented in our earlier paper [2], [5]. About 36 cm3 of the solvent (pentanols) was introduced into the equilibrium cell (volume  40 cm3), and the accurate quantity was determined by mass. Then the equilibrium cell was immersed in a constant-temperature bath (filled with ethylene glycol + water) and connected to a supply of helium. The temperature was controlled to within ±0.02 K and measured with a quartz thermometer (Hewlett–Packard Co., Model 2804A)

Results and discussion

The Henry’s law constants and the infinite dilution activity coefficients measured in this work are numerically indicated in TABLE 1, TABLE 2, TABLE 3 for the 1-pentanol, 2-pentanol, and 3-pentanol systems, respectively. Because all experiments were conducted under atmospheric pressure, the estimated fugacity coefficients of the solute in the vapor phase and the compressibility factors of the vapor were around unity (ϕgV=1, Z = 1) for all systems. However, for the evaluation of the infinite

Conclusions

Henry’s law constants and the infinite dilution activity coefficients of eight gases in 1-pentanol, 2-pentanol in the temperature range of (250 to 330) K and 3-pentanol in the temperature range of (260 to 330) K have been obtained from gas stripping measurements. The Henry’s law constant did not depend on the nonideality of the vapor for the systems studied in this work. On the other hand, the nonideality of the solute at the reference state should be considered in order to obtain infinite

Acknowledgement

This paper reports part of the work supported by a Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (16560663), which is gratefully acknowledged.

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