Isobaric VLE data for 1-methyl-3-ethylbenzene or 1-methyl-4-ethylbenzene + 1, 2, 4-trimethylbenzene at 20 kPa

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Abstract

Isobaric VLE data for 1-methyl-3-ethylbenzene (1M3EB) or 1-methyl-4-ethylbenzene (1M4EB) + 1, 2, 4-trimethylbenzene (124TMB) at 20 kPa were determined with a modified Rose–Williams type recirculation still. Herington area test method was used to test the thermodynamic consistency, showing good quality. The thermodynamic models of Wilson, NRTL, and UNIQUAC were used to correlate the measured data. All the three models represented the measurements well. Positive deviation behavior was observed for the 1M3EB + 124TMB system, while negative deviation behavior was observed for the 1M4EB + 124TMB system. The information presented in the paper is essential for the design and operation of distillation columns for the separation of the mixtures.

Highlights

► VLE data of 1E3MB or 1E4MB and 124TMB at 20 kPa were measured. ► VLE data were correlated by three models of Wilson, NRTL, and UNIQUAC. ► Different deviation behavior was observed for the two systems investigated.

Introduction

Mixtures of aromatic hydrocarbons with nine carbon atom (C9) are important byproduct of reforming unit in petroleum processing. After 1, 3, 5-trimethylbenzene (denoted as 124TMB) is drawn using extraction distillation [1], [2], [3], the residual streams are mainly composed of 1, 2, 4-trimethylbenzene (denoted as 124TMB), 1-methyl-3-ethylbenzene (denoted as 1E3MB), 1-methyl-4-ethylbenzene (denoted as 1E4MB) from here onwards and other impurities.

VLE data at the operating pressure are indispensable for separation by distillation. Among the studies on (vapor + liquid) equilibrium data determination of C9 aromatic hydrocarbons, isobaric data of 135TMB + 124TMB at 98.7 kPa have been measured by Liu et al. [4].

In the present study, to separate 124TMB from the residual streams, we measured the isobaric VLE data for the two binary systems of 1E3MB or 1E4MB and 124TMB at 20 kPa by using a modified Rose–Williams type recirculation still. The determined VLE data were verified with the thermodynamic consistency test described by Herington and improved by Abobott and Van Ness [5], [6]. Three activity coefficient models of Wilson [7], nonrandom two-liquid (NRTL) [8], and universal quasichemical (UNIQUAC) [9] were adopted to correlate the investigated experimental data.

Section snippets

Chemicals

Both 1E3MB (AR) and 1E4MB (AR) supplied by Shanghai Chemical Reagent Corporation (China), were further purified by distillation. 124TMB, supplied by Jinling Petroleum Chemical Corporation, was used without further purification. All of the chemicals have been analyzed by gas chromatography (SP6890A, Shandong Lunan Ruihong Chemical Instruments Co., Ltd China). The densities and refractive indexes of two components were measured by a digital vibrating-tube densimeter (DMA 4500, Anton Paar,

Experimental data

The measured isobaric VLE data for the two binary systems of 1E3MB (1) or 1E4MB (1) + 124TMB (2) at 20 kPa were listed in TABLE 2, TABLE 3, respectively. Txy phase diagrams of the two systems, illustrated in FIGURE 1, FIGURE 2 showed no azeotropic behavior.

Thermodynamic consistency test

Herington area test method [5], [6] was used to check the thermodynamic consistency for all the experimental data. According to Herington method, if D  J < 10, the experimental data would be considered thermodynamically consistent, in which D and

Conclusions

(Vapor + liquid) equilibrium data of 1E3MB or 1E4MB + 124TMB systems at 20 kPa were measured by using a modified Rose–Williams type still. NRTL, Wilson, and UNIQUAC model parameters were obtained with satisfactory correlation. Slightly better correlation results were observed with the UNIQUAC model for 1E3MB + 124TMB and the Wilson model for 1E4MB + 124TMB. The experimental data does not exhibit any azeotropic behavior for the two binary systems. The measured (vapor + liquid) equilibrium data provide the

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