Elsevier

Fluid Phase Equilibria

Volume 293, Issue 2, 25 June 2010, Pages 157-163
Fluid Phase Equilibria

Phase equilibria on five binary systems containing 1-butanethiol and 3-methylthiophene in hydrocarbons

https://doi.org/10.1016/j.fluid.2010.02.030Get rights and content

Abstract

Isothermal vapor–liquid equilibrium (VLE) of the following systems was measured with a recirculation still: 1-butanethiol + methylcyclopentane at 343.15 K, 1-butanethiol + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + toluene at 383.15 K, 3-methylthiophene + o-xylene at 383.15 K, and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K. 1-Butanethiol + methylcyclopentane and 1-butanethiol + 2,2,4-trimethylpentane systems exhibit positive deviation from Raoult's law, whereas systems containing 3-methylthiophene in aromatic hydrocarbons exhibit only slight positive deviation from Raoult's law. A maximum pressure azeotrope was found in the system 1-butanethiol + 2,2,4-trimethylpentane (x1 = 0.548, P = 100.65 kPa, T = 368.15 K). The experimental results were correlated with the Wilson model and compared with original UNIFAC and COSMO-SAC predictive models. Raoult's law can be used to describe the behavior of 3-methylthiophene in aromatic hydrocarbons at the experimental conditions in this work. Liquid and vapor-phase composition were determined with gas chromatography. All measured data sets passed the thermodynamic consistency tests applied. The activity coefficients at infinite dilution are also presented.

Introduction

Stringent air quality regulations impose the use of ultra-low sulfur gasoline and diesel in many countries [1]. In Europe, the sulfur level in gasoline and diesel should be lower than 10 ppm beginning from 2009 [2]. New developments on sulfur separation process design to further decrease the sulfur level have become one of the major challenges to the refining industry [3]. Design of separation processes to accomplish the removal of sulfur compounds requires the knowledge of the behavior of sulfur compounds in hydrocarbons. Information of such systems is scarce and experimental work is required. 1-Butanethiol and 3-methylthiophene are typical organic sulfur compounds present in the hydrocarbon streams originating from the fluid catalytic cracker (FCC) [4], [5].

In this work, we measured vapor–liquid equilibrium (VLE) for the systems 1-butanethiol + methylcyclopentane at 343.15 K, 1-butanethiol + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + toluene at 383.15 K, 3-methylthiophene + o-xylene at 383.15 K, and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K with a recirculation still. No other VLE data of the binary systems studied in this work have been found in the literature search.

In the previous studies, Sapei et al. [6], [7] measured VLE data for the systems 3-methylthiophene + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + 2,4,4-trimethyl-1-pentene at 368.15 K, 3-methylthiophene + cyclohexane at 348.15 K, 3-methylthiophene + 1-hexene at 333.15 K, 3-methylthiophene + 2-methylpentane at 333.15 K, 3-methylthiophene + n-hexane at 333.15 K, 3-methylthiophene + methylcyclopentane at 343.15 K, and 3-methylthiophene + methylcyclohexane at 373.15 K. Kilner et al. [8] measured vapor–liquid equilibrium for system 1-butanethiol + n-hexane and 1-butanethiol + toluene for mole fractions x = 0–0.2 of 1-butanethiol at temperatures between 323 and 373 K.

Section snippets

Materials

1-Butanethiol, 3-methylthiophene, methylcyclopentane, 2,2,4-trimethylpentane, toluene, o-xylene, and 1,2,4-trimethylbenzene were provided by Sigma–Aldrich, Finland. The purity of all substances was checked by gas chromatography (GC) equipped with a flame ionization detector (FID). All chemicals were dried over molecular sieves (Merck 3Å) for 24 h. The refractive indexes, nD, of the pure liquids were measured at 298.15 K with ABBEMAT-HP automatic refractometer (Dr. Kernchen, Germany) with accuracy

Vapor pressure measurements

Vapor pressure of 3-methylthiophene, methylcyclopentane, 2,2,4-trimethylpentane, toluene, and o-xylene were measured in the previous studies [6], [7], [13], [14], [15]. The Antoine parameters for 1-butanethiol and 1,2,4-trimethylbenzene were regressed from the vapor pressures measured in this work. These parameters with the recommended temperature range of the vapor pressure equations are presented in Table 3. The average absolute deviation of pressure (ΔPSaver) between measured (Pi,exp) and

Conclusions

Vapor pressures of 1-butanethiol and 1,2,4-trimethylbenzene were measured and compared with the literature data. The agreement between vapor pressures measured in this work and found in the literature was good. Isothermal VLE data for the systems 1-butanethiol + methylcyclopentane at 343.15 K, 1-butanethiol + 2,2,4-trimethylpentane at 368.15 K, 3-methylthiophene + toluene at 383.15 K, 3-methylthiophene + o-xylene at 383.15 K, and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K with a recirculation

Acknowledgements

The authors acknowledge Neste Jacobs Oy and Neste Oil Oyj for the financial support.

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    • Isobaric vapor-liquid equilibrium for four binary systems of 3-methylthiophene

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      However, up to now, only few papers have reported the VLE data for the thiophenic compounds. In the case of 3-methylthiophene, which is one of the representative sulfurs in gasoline, only Sapei et al. have reported its VLE data, including 3-methylthiophene + 2-methylpentane at 333.15 K [6], 3-methylthiophene + n-hexane at 333.15 K [6], 3-methylthiophene + methylcyclopentane at 343.15 K [6], 3-methylthiophene + methylcyclohexane at 373.15 K [6], 3-methylthiophene + cyclohexane at 348.15 K [7], 3-methylthiophene + 2,2,4-trimethylpentane at 368.15 K [7], 3-methylthiophene + toluene at 383.15 K [8], 3-methylthiophene + o-xylene at 383.15 K [8] and 3-methylthiophene + 1,2,4-trimethylbenzene at 383.15 K [8]. Moreover, all the VLE data of 3-methylthiophene published by Sapei were measured under isothermal conditions.

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