Elsevier

Fluid Phase Equilibria

Volume 409, 15 February 2016, Pages 78-83
Fluid Phase Equilibria

Experimental isobaric (vapor + liquid) equilibrium data for the binary system N, N-dimethyl formamide + dimethyl sulfoxide and the quaternary system sec-butyl alcohol + sec-butyl acetate + N, N-dimethyl formamide + dimethyl sulfoxide at 101.3 kPa

https://doi.org/10.1016/j.fluid.2015.09.039Get rights and content

Abstract

Isobaric vapor–liquid equilibrium (VLE) data for the quaternary system sec-butyl alcohol + sec-butyl acetate + N, N-dimethyl formamide (DMF) + dimethyl sulfoxide (DMSO) and the constituent binary system DMF + DMSO were determined at 101.3 kPa with a modified Othmer still. The measured experimental data of binary and quaternary systems were certified to be thermodynamically consistent according to the Van Ness method. And the experimental binary data were correlated by Wilson, NRTL and UNIQUAC activity coefficient models. The rest of binary interaction parameters have been obtained in our previous work. Then, the binary and quaternary vapor–liquid equilibrium were predicted by the models with the correlated parameters. The results show that the three models yield a good prediction for the binary and quaternary systems. But NRTL model performed better than the other two models in predicting VLE of the quaternary system.

Introduction

sec-Butyl alcohol is widely used in industry, such as pharmaceutical intermediates, spices, dyes, flotation agents, polymerization additives, rubber additives, the solubilizers of nitrocellulose lacquer and nitrocellulose lacquer thinner and so on. But by now, it is mainly used to produce methyl ethyl ketone [1], [2]. The traditional methods of producing sec-butyl alcohol are indirect and direct hydration of butylene. The method of indirect hydration of butylene has two serious drawbacks: first, serious corrosion to equipment because of sulfuric acid as catalyst; second, low selectivity. Although the process of direct hydration of butylenes has overcome the drawback of corrosion, it requires high purity of raw material and has low conversion ratio [3], [4]. Recently, a novel method of producing sec-butyl alcohol by transesterifying sec- butyl acetate with alcohols was exploited by some researchers, which is superior to traditional method by the hydration of butylenes. In this new process, sec-butyl alcohol and sec-butyl acetate form a “pseudo-azeotrope”, in which the vapor and liquid composition is so close that it should be ignored nearly [5]. Extractive distillation as a special distillation is suitable to separate this type of systems. And Extractive agent selection is important aspect for a process of extractive distillation.

In our previous work, DMF (3) and DMSO (4) were certified to be effective extractive solvents for separation of sec-butyl alcohol (1) and sec-butyl acetate (2) and DMSO performed better than DMF [5], [6]. But the boiling point of DMSO is so high that it is likely to decompose when recovering extractive agent by distillation at 1 atm and even can cause explosion. If DMSO and DMF are mixed as extractive agent, the temperature of tower bottom can be reduced. At same time, DMF can inhibit the dissociation of DMSO at high temperature [7]. Consequently, the mixed solvent as extractive agent to separate sec-Butyl alcohol (1) and sec-Butyl acetate (2) is better than a single agent such as DMF (3) or DMSO (4) in industrial applications. So, it is necessary to measure isobaric VLE data for the quaternary system sec-Butyl alcohol (1) + sec-Butyl acetate (2) + DMF (3) + DMSO (4) and the constituent binary systems. The binary interactive parameters of the five systems: sec-butyl alcohol (1) + sec- butyl acetate (2) [8], sec-butyl alcohol (1) + DMF (3) [5], sec-butyl alcohol (1) + DMSO (4) [6], sec-butyl acetate (2) + DMF (3) [5], sec-butyl acetate (2) + DMSO (4) [6] have been obtained in our previous work. Guo L. et al. measured vapor pressure of the binary system of DMF (3) + DMSO (4) at various temperature and concentrations by using a quasi-static ebulliometer method [7]. But there is no isobaric VLE data for DMF (3) + DMSO (4) system and sec-butyl alcohol (1) + sec-butyl acetate (2) + DMF (3) + DMSO (4) system in open literatures. Thus, the absent isobaric VLE data for the two systems were explored experimentally in this work to supply basic data for the separation of sec-butyl alcohol (1) + sec-butyl acetate (2) by extractive distillation using the mixed solvent of DMF (3) and DMSO (4) as extractive agent.

Section snippets

Chemicals

In this work, Analytical reagents (AR), sec-butyl alcohol, sec-butyl acetate and DMF and DMSO were used. The molecular formula, CASRN, source, grade and mass fraction are listed in Table 1. The physical properties of the pure components are listed in Table 2, which are used to calculate fugacity coefficients. Purity of all these chemicals were checked by a gas chromatography (GC) equipped with a flame ionization detector (FID) and no appreciable peak of impurity was detected. And the water

Experimental data

The experimental VLE data of the binary system of DMF (3) + DMSO (4) and the quaternary system of sec-butyl alcohol (1) + sec-butyl acetate (2) + DMF (3) + DMSO (4) were measured with a modified Othmer still mentioned above at 101.3 kPa. The experimental data are listed in Table 4, Table 5.

Vapor-liquid equilibrium model

For low pressure and considering vapor non-ideality, the flowing Equation (1) [19], [20] is valid to describe VLE,ϕˆiyiP=xiγiϕisPis,(i=1,2,N)where γi is the activity coefficient of component i in liquid

Conclusion

The VLE data of binary system of DMF (3) + DMSO (4) and quaternary sec-butyl alcohol (1) + sec-butyl acetate (2) + DMF (3) + DMSO (4) were measured with a modified Othmer still. The experimental VLE data have passed the Van Ness thermodynamic consistency test. Then the binary VLE data were correlated with Wilson, NRTL and UNIQUAC models and obtained their binary interaction parameters. And the VLE data for the binary and quaternary systems were predicted by the three models with these binary

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