(Liquid + liquid) equilibria in {water + acrylic acid + (1-butanol, or 2-butanol, or 1-pentanol)} systems at T = 293.2 K, T = 303.2 K, and T = 313.2 K and atmospheric pressure

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Abstract

(Liquid + liquid) equilibrium (LLE) data for {water + acrylic acid + (1-butanol, or 2-butanol, or 1-pentanol)} at T = 293.2 K, T = 303.2 K, and T = 313.2 K and atmospheric pressure (≈95 kPa) were determined by Karl Fischer titration and densimetry. All systems present type I binodal curves. The size of immiscibility region changes little with an increase in temperature, but increases according to the solvent, following the order: 2-butanol < 1-butanol < 1-pentanol. Values of solute distribution and solvent selectivities show that 1-pentanol is a better solvent than 1-butanol or 2-butanol for acrylic acid removal from water solutions. Quality of data was ascertain by Hand and Othmer-Tobias equations, giving R2 > 0.916, mass balance and accordance between tie lines and cloud points. The NRTL model was used to correlate experimental data, by estimating new energy parameters, with root mean square deviations below 0.0053 for all systems.

Highlights

Acrylic acid solubilizes preferably in the studied solvents than in water. ► Immiscibility region increases in the order: 2-butanol < 1-butanol < 1-pentanol. ► Immiscibility region reduces little with an increase in temperature. ► K and S values show that 1-pentanol is the best studied solvent.

Introduction

Acrylic acid and its derivatives are the principal raw materials in polymer manufacturing [1]. These polymers are used in superabsorbent materials [2], [3], adhesives [4], [5], surface coatings [6], [7], etc. Acrylic acid production represented 2.8 million tons annually in 1995 [8] and increased to 3.4 million tons annually in 2003 [9]. Conventionally, acrylic acid is prepared by the oxidation of propene; an alternative way is the use of sugar fermentation. In this case, acrylic acid is produced as a diluted aqueous solution, which must be separated and purified.

An option for removal acrylic acid from aqueous solution is liquid–liquid extraction. However, (liquid + liquid) equilibrium data in aqueous systems with acrylic acid are extremely scarce. For instance, Linek et al. [10] and Chubarov et al. [11], [12] studied this kind of systems with several organic acids and esters. In this work, (liquid + liquid) equilibrium data on the system {water + acrylic acid + (1-butanol, or 2-butanol, or 1-pentanol)} were determined at T = 293.2 K, T = 303.2 K, and T = 313.2 K by using Karl Fischer titration and densimetry. The data were correlated with the NRTL model for the activity coefficient, showing a good agreement between experimental and calculated data. The quality of data was ascertained by the Hand and Othmer-Tobias correlations, mass balance showed by the proximity of tie lines to feed points, and accordance between tie lines and cloud points compositions.

Section snippets

Experimental

The physical properties of the compounds utilized here are shown in table 1. Acrylic acid (Fluka), hexanoic acid (Aldrich), 1-butanol (Merck), 2-butanol (Vetec), and 1-pentanol (Acros) with purity mass fraction >0.99, >0.995, >0.995, 0.99, and 0.99, respectively, were used as received. Water was distilled and deionized before used.

Binodal curves are determined by the cloud point method, in which a third component is slowly added to a binary, homogeneous mixture previously inserted in an

Thermodynamic modeling

The non-random two-liquid model (NRTL) [18], based on the local composition concept, is used to correlate the experimental data. The NRTL equations are given by:lnγi=jτjiGjixjkGkixk+jxjGijkGkjxkτij-kxkτkjGkikGkjxk,τij=ΔgijRT=Aij+BijT(τijτji),Gij=exp(-αijτij)(αij=αji).Subscripts i, j, and k refer to each component, x is the mole fraction, γ is the activity coefficient, τ is the characteristic energy binary interaction parameter, α is the mixture non-randomness adjustable parameter, A and B

Results and discussion

Binodal curves were obtained for (water + acrylic acid + hexanoic acid) system at T = 296.2 K and atmospheric pressure of ≈95 kPa (as a validation system) and for {water + acrylic acid + (1-butanol, or 2-butanol, or 1-pentanol)} systems at T = 293.2 K, T = 303.2 K, and T = 313.2 K and ≈95 kPa. These results are presented in TABLE 2, TABLE 3, TABLE 4, TABLE 5.

The cloud points density values, presented in TABLE 2, TABLE 3, TABLE 4, TABLE 5, were used to find expressions for density as function of water (w1) and

Conclusions

(Liquid + liquid) equilibrium data for {water + acrylic acid + (1-butanol, or 2-butanol, or 1-pentanol)} at T = 293.2 K, T = 303.2 K, and T = 313.2 K and atmospheric pressure (≈95 kPa) were determined. The systems presented type I binodal curves and, although the immiscibility region size changes little with temperature, it changes significantly with the type of solvent used in the order: 2-butanol < 1-butanol < 1-pentanol. The data shows that 1-pentanol is a better solvent than 1-butanol or 2-butanol to remove

Acknowledgements

Authors acknowledge financial support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP-Brazil). M. Aznar is the recipient of a fellowship from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil).

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