Investigation of the isothermal (vapour + liquid) equilibria of aqueous 2-amino-2-methyl-1-propanol (AMP), N-benzylethanolamine, or 3-dimethylamino-1-propanol solutions at several temperatures

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Abstract

The vapour pressures of (2-amino-2-methyl-1-propanol (AMP) + water), (N-benzylethanolamine + water), or (3-dimethylamino-1-propanol + water) binary mixtures, and of pure AMP and 3-dimethylamino-1-propanol components were measured by means of two static devices at temperatures between 283 K and 363 K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions (GE) were calculated for several constant temperatures and fitted to a fourth-order Redlich–Kister equation using the Barker’s method. The {2-amino-2-methyl-1-propanol (AMP) + water} binary mixture exhibits negative deviations in GE (at T < 353.15 K) and a sinusoidal shape for GE for the higher temperatures over the whole composition range. For the aqueous N-benzylethanolamine solution, a S shape is observed for the GE for all investigated temperatures over the whole composition range. The (3-dimethylamino-1-propanol + water) binary mixture exhibits negative deviations in GE (at T < 293.15 K), positive deviations in GE (for 293.15 K < T < 353.15 K) and a sinusoidal shape for GE for the higher temperatures over the whole composition range.

Introduction

Aqueous alkanolamine solutions are widely used for the removal of the acid gases (CO2 and H2S) from gas mixtures. In addition to the well-established industrial uses of experimental data for these completely miscible (alkanolamine + water) systems, there is a general scientific interest in using such experimental data in combination with theories or mathematical models to improve our understanding of molecular interactions in non-ideal liquid systems. (Vapour + liquid) equilibria (VLE) data for (alkanolamine + water) systems are rarely available in the literature.

The present paper is part of a research program on (VLE) in aqueous mixtures of alkanolamines. VLE data for binary mixtures containing {methylethanolamine (MEA) + water}, or (4-methylmorpholine + water) have been reported previously [1]. The purpose of the present work is to investigate VLE of {2-amino-2-methyl-1-propanol (AMP) (CAS # 124-68-5) + water}, {N-benzylethanolamine (CAS # 104-63-2) + water}, or {3-dimethylamino-1-propanol (CAS # 3179-63-3) + water} binary mixtures with a view to use the results to determine interaction parameters for predictive group contribution methods. A survey of the literature shows that there is only one data set available for the (AMP + water) system [2].

Section snippets

Experimental

The alkanolamines were supplied by Aldrich Chem. (Milwaukee, WI, USA). They were used without further purification. The purities, tested by GLC, were better than mass fraction purity 0.99. Aqueous solutions were prepared from distilled and deionised water.

For the pure AMP and 3-dimethylamino-1-propanol components, the vapour pressure measurements were carried out using a static apparatus. The description of the apparatus and the experimental procedure can be found elsewhere [3], [4], [5], [6],

Results and discussion

The experimental vapour pressure data were fitted to the Antoine equation:lg10P/Torr=A-BC+t/(°C).The objective function Q was the sum of the squared relative deviations in pressure:Q=Pcalc-PexpPexp2.The overall mean relative deviation in pressure is:δPP%=100NPcalc-PexpPexp,where N is the total number of experimental values.

Table 1 lists, for the pure AMP and 3-dimethylamino-1-propanol components, the temperature range, the coefficients A, B, C of the Antoine equation and the overall mean

Summary

Vapour pressures of pure AMP and 3-dimethylamino-1-propanol have been measured using a static device and correlated with the Antoine equation. Isothermal VLE data of aqueous AMP, N-benzylethanolamine, or 3-dimethylamino-1-propanol solutions were studied at several temperatures using a second static device. The aqueous AMP solution exhibits negative deviations in GE (at T < 313.15 K) and a sinusoidal shape for GE for the higher temperatures. For the (N-benzylethanolamine + water) binary mixture, a S

Acknowledgement

This work has been done in the framework of the international project PHC TASSILI (Ref. 09 MDU 761).

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