Isothermal and isobaric vapor–liquid equilibria for the binary system trimethylbenzoquinone + n-hexanol
Introduction
Trimethylbenzoquinone, 2,3,5-trimethy-l,4-benzoquinone (TMBQ, CAS RN 935-92-2), is a key intermediate in the production of vitamin E [1]. Today, the oxidation of 2,3,6-trimethyphenol in n-hexonal as solvent using clean and cheap oxidant is one of the main routes for industrial production of TMBQ and trimethyl-hydroquinone (TMHQ) [2]. The vapor–liquid equilibria data for the binary system TMBQ + n-hexanol are needed for the modeling and simulation of the separation of TMBQ and n-hexanol by distillation. Unfortunately, the VLE data for this system have not been reported.
In this paper, isothermal and isobaric VLE for TMBQ + n-hexanol at the temperatures T = 393.15, 403.15 and 413.15 K, and at the pressure p = 20.00 kPa, are reported. The binary VLE data of this system are correlated using the UNIQUAC equation with the temperature-dependent binary parameters. Experimental vapor pressures of TMBQ and n-hexanol are also included.
Section snippets
Experimental
TMBQ (highest commercial grade, Zhejiang NHU Co., Ltd.) was maintained under special conditions before use. It was distilled using a 150 cm high column under the pressure of 10.0 kPa. n-Hexanol (analytical reagent grade, Shanghai Chemical Co.) was refluxed over freshly activated CaO for at least 2 h and then fractionally distilled [3]. The pure materials were stored over type 0.4 nm molecular sieves. The purities of the materials were determined by gas chromatography. The purity of TMBQ was 99.75
Results and discussion
Ebulliometric method is based on the overall concentration instead of the equilibrium concentration xi of liquid phase. But for the systems with components largely differing in boiling points, the difference between and xi is not negligible. The equilibrium liquid composition correction becomes critical. The equilibrium liquid composition xi, is related to the overall composition , by the following nonlinear equation,where f is the reflux ratio
Acknowledgements
This work was financed by Zhejiang Province Natural Science Foundation of China (No. RC01051) and Postdoctoral Natural Science Foundation of China (No. 2003033536).
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