Vapour–liquid equilibrium for the systems diethyl sulphide + 1-butene, +cis-2-butene, +2-methylpropane, +2-methylpropene, +n-butane, +trans-2-butene

doi:10.1016/j.fluid.2010.01.006

Fluid Phase Equilibria

Volume 291, Issue 2, 15 May 2010, Pages 180-187

https://doi.org/10.1016/j.fluid.2010.01.006 Get rights and content

Abstract

Isothermal vapour–liquid equilibrium was measured for the systems of diethyl sulphide + 1-butene, +cis-2-butene, and +2-methylpropene at 312.6 K, diethyl sulphide + n-butane was measured at 317.6 K, diethyl sulphide + trans-2-butene at 317.5 K, and diethyl sulphide + 2-methylpropane at 308.0 K. The pressure–temperature–total composition data were converted into pressure–temperature–liquid–vapour composition data using the method of Barker. Error estimates are provided for each variable. The isothermal parameters for the Wilson, NRTL and UNIQUAC activity coefficient models were regressed. The measurements were compared with the predictions by COSMO segment activity coefficient (COSMO-SAC) and UNIFAC.

Introduction

Due to the extensive contribution of vehicles exhaust gases to air pollution, the governments of many countries introduced new stringent regulations on the sulphur content in fuels. This showed the necessity of an improvement in sulphur removal technologies. Petrol produced by fluid catalytic cracking (FCC) represents about 30–40% of the total petrol production and it is the most important sulphur contributor in fuel. The most abundant organic sulphur components in FCC petrol are thiols, sulphides, thiophene and alkylthiophenes, tetrahydrothiophene, thiophenols and benzothiophene [1], [2]. Many of these compounds are not present in the feedstock to FCC, therefore they are formed either from the direct transformation of sulphur compounds present in the feedstock or from their reactions with FCC products [1]. Diethyl sulphide is one of the products of the reactions undergone by organic sulphur compounds in the FCC units [2], [3].

The development and improvement of chemical units is often made by simulation with process balances and thermodynamic models. Experimental data are the basis on which such models lay. Vapour–liquid equilibrium (VLE) measurements provide the information needed to model separation processes.

The aim of this work was to measure VLE data of diethyl sulphide in C4-hydrocarbons. Experiments for the binary systems of diethyl sulphide + 1-butene, +cis-2-butene, and +2-methylpropene were conducted at 312.6 K, diethyl sulphide + n-butane was measured at 317.6 K, diethyl sulphide + trans-2-butene at 317.5 K, and finally diethyl sulphide + 2-methylpropane at 308.0 K. Wilson [4], NRTL [5] and UNIQUAC [6] isothermal parameters were regressed. No comparable measurements were found in the literature for any of the systems measured in this work.

Vapour–liquid equilibrium can be modelled by means of predictive methods, when the experimental data available are scarce or none. Predictive methods are, however, less accurate than the optimised Wilson, NRTL or UNIQUAC models. UNIFAC [7] predicts VLE using the concept of group contributions. The COSMO segment activity coefficient (COSMO-SAC [8]) model bases its prediction on the use of solvation thermodynamics and computational quantum mechanics [9]. The data measured in this work were compared, when possible, with the results from these predictive methods.

Section snippets

Materials

The materials purities and their suppliers are listed in Table 1. Diethyl sulphide was degassed prior its use according to the procedure by Van Ness and Abbot [10], with the modifications by Fischer and Gmehling [11]. The C4-hydrocarbons were degassed by evacuation in a syringe pump. The vacuum line was opened 10 times in a 10 s period. The comparison of the measured vapour pressures of the pure components with literature values was made to check the quality of the degassing procedure. Such

VLE measurements

The results of the VLE measurements for the 6 binary systems are listed in Table 4, Table 5, Table 6, Table 7, Table 8, Table 9, along with the estimated errors. The injected moles amount is given in the tables with more decimals than required in order to permit the repetition of our calculations. Fig. 2 shows the total pressure as a function of the liquid and vapour composition for the six binaries studied in this work. None of the binary pairs showed azeotropic behaviour.

The regressed

Conclusions

Isothermal vapour–liquid equilibrium data were measured for six binary systems of C4-hydrocarbons + diethyl sulphide using a static total pressure apparatus. The liquid and vapour phase compositions were calculated from the total pressure measurements with the method of Barker. The fugacity coefficients were modelled with the Soave–Redlich–Kwong equation of state and the activity coefficients with the Legendre polynomials. Error analysis was performed on all the variables.

The isothermal

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Vapour–liquid equilibrium for the systems diethyl sulphide + 1-butene, +cis-2-butene, +2-methylpropane, +2-methylpropene, +n-butane, +trans-2-butene

Abstract

Introduction

Section snippets

Materials

VLE measurements

Conclusions

Appl. Catal. A

Fluid Phase Equilib.

Chem. Eng. Sci.

Fluid Phase Equilib.

Fluid Phase Equilib.

Ind. Eng. Chem. Res.

J. Inst. Petrol

J. Am. Chem. Soc.

AIChE J.

AIChE

AIChE J.

Ind. Eng. Chem. Res.

Ind. Eng. Chem. Res.