Phase equilibrium and separation of n-dodecane–toluene–phenol in low temperature coal tar

ZHANG Haiyong1 LIU Qian1 LIU Xingkun1 ZHANG Xianglan1 XIE Qiang1 WANG Yonggang1

(1.School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing) , Beijing, China 100083)

【Abstract】The group separation of low temperature coal tar (LTCT) is important for its effective utilization. With n-dodecane, toluene and phenol as model compounds, the liquid–liquid-equilibrium (LLE) of alkane-aromaticsphenol ternary system in LTCT were obtained by experimental method and Aspen Plus simulation. The LLE of typical ternary systems during separation of the mixture by N,N-dimethylformamide (DMF) water solution were also simulated. The results showed that the ternary phase diagram simulated by Aspen Plus through UNIF-LL model fitted well with the experimental data. Toluene as a cosolvent promoted n-dodecane–toluene–phenol to be a homogeneous system. According to the solubility difference of n-dodecane, toluene and phenol in DMF and with the Hansen solubility parameters theory, n-dodecane and toluene could be separated successively from their homogeneous mixture by DMF in which different contents of water were added to adjust the polarity of solvent. Based on the optimization of extraction temperature, solvent/oil ratio and water content in solvent, n-dodecane with 93.2% purity was separated by one stage extraction with DMF, and after phase separation, toluene with 93.4% purity was obtained by adding water weighted 30% of DMF to the extract phase at 303 K and 1.5 solvent/oil ratio.

【Keywords】 low temperature coal tar; liquid–liquid phase equilibria; Aspen Plus; simulation; solvent extraction; separation;


【Funds】 State Key Research and Development Program of China (2016YFB0600305) National Natural Science Foundation of China (21506251)

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(Translated by MA XQ)


    [1] GUO S C, HU H Q. Coal Chemical Technology [M]. 3rd ed. Beijing: Chemical Industry Press, 2012: 6–8 (in Chinese).

    [2] GU X H. Properties and utilization of coal direct liquefaction residue [J]. Clean Coal Technology, 2012, 18 (3): 63–66 (in Chinese).

    [3] WANG Y F. Separation and character analysis of low temperature coal tar composition [J]. Journal of Yangtze University (Natural Science Edition), 2012, 9 (5): 26–28 (in Chinese).

    [4] CONG X S. Separation techniques and application of coal tar [J]. Journal of Zaozhuang University, 2009, 26 (2): 69–72 (in Chinese).

    [5] ZHAO P, PEI X F, WANG Z Z. Study on the present situation of medium/low temperature coal tar processing and utilization [J]. Coal Quality Technology, 2016, (6): 11–16 (in Chinese).

    [6] SUN H Q, QU S J, WANG L B. Present situation on production and processing use of low temperature coal tar [J]. Clean Coal Technology, 2008, 14 (5): 34–38 (in Chinese).

    [7] ZHANG X J. Hydrogenating process for coal tar from mid-low temperature coal carbonization [J]. Journal of China Coal Society, 2011, 36 (5): 840–844 (in Chinese).

    [8] ZHU Y F. Hydro-conversion technologies of coal tar [J]. Clean Coal Technology, 2014, 20 (3): 43–48 (in Chinese).

    [9] RADWAN G M, AL-MUHTASEB S A, FAHIM M A. liquid–liquid equilibria for the extraction of aromatics from naphtha reformate by dimethylformamide/ethylene glycol mixed solvent [J]. Fluid Phase Equilibria, 1997, 129 (1/2): 175–186.

    [10] LI Y, QIAO H Y, SHI W W et al. Coal tar separation by extraction and product properties [J]. Petroleum Processing and Petrochemicals, 2017, 48 (3): 58–62 (in Chinese).

    [11] XUE F F, LI D, ZHANG L N et al. Composite extractant of liquid–liquid extraction aromatics for the coal-derived naphtha [J]. Chemical Industry and Engineering Progress, 2017, 36 (8): 2897–2902 (in Chinese).

    [12] WU H, LIU C J, XIAO C. Determination and correlation of liquid–liquid equilibrium data for a tetranap–n-decane–dimethyl sulfoxide system [J]. Journal of Chemical Engineering of Chinese Universities, 2016, 30 (5): 985–991 (in Chinese).

    [13] DONG H, YANG X, YUE G et al. (Liquid + liquid) equilibria for benzene + cyclohexane + N,N-dimethylformamide + sodium thiocyanate [J]. Journal of Chemical Thermodynamics, 2013, 63: 169–172.

    [14] SONG S, LIN C, YOU N. Phase equilibria Study of the (benzene + cyclohexane + N,N-dimethylformamide + potassium thiocyanate) quaternary systems [J]. Fluid Phase Equilibria, 2014, 376: 154–158.

    [15] LEI Z G, ZHOU R Q, DUAN Z T. Separation on the aromatics and paraffin by extractive distillation with NMP [J]. Journal of Chemical Engineering of Chinese Universities, 2001, 15 (2): 183–186 (in Chinese).

    [16] YANG Y M, HU J, HAO C et al. Separation of o-xylene and m-xylene by extractive distillation with salt [J]. Modern Chemical Industry, 2016, 36 (4): 173–175 (in Chinese).

    [17] LIN Z, HOU Y, REN S et al. Phase equilibria of phenol + toluene + quaternary ammonium salts for the separation of phenols from oil with forming deep eutectic solvents [J]. Fluid Phase Equilibria, 2016, 429: 67–75.

    [18] YE C S, LIN C, QIU T. Determination and correlation of liquid–liquid equilibrium data for the ternary system of DMF–CHCl3–H2O [J]. Journal of Chemical Engineering of Chinese Universities, 2009, 23 (2): 183–186 (in Chinese).

    [19] WANG L, LI R L, SUN L T et al. Studies on phase equilibrium of tertbutanol in supercritical CO2 [J]. Chem. J. Chinese Universities, 2009, 30 (8): 1631–1635 (in Chinese).

    [20] UEMASU I, KUSHIYAMA S. Selective separation of benzene from hydrocarbon mixtures via liquid–liquid extraction method using aqueous solutions of substituted cyclodextrins [J]. Fuel Processing Technology, 2004, 85 (13): 1519–1526.

    [21] MA G R, CHEN X C, YU G R. Determination of LLE data for toluene–hexamethyldisiloxane–sulfolane ternary system [J]. Journal of Beijing University of Chemical Technology, 2003, 30 (3): 5–9 (in Chinese).

    [22] DEENADAYALU N, NGCONGO K C, LETCHER T M et al. liquid–liquid equilibria for ternary mixtures (an ionic liquid + benzene + heptane or hexadecane) at T = 298.2 K and atmospheric pressure [J]. Journal of Chemical & Engineering Data, 2006, 52 (1): 988–991.

    [23] LIN W C, TSAI T H, LIN T Y et al. Influence of the temperature on the liquid–liquid equilibria of heptane + toluene + sulfolane and heptane + m-xylene + sulfolane [J]. Journal of Chemical & Engineering Data, 2008, 53 (3): 760–764.

    [24] JIANG G C, ZHANG S J, WANG Y G et al. Selective separation of aromatic hydrocarbons from low temperature coal tar [J]. CIESC Journal, 2015, 66 (6): 2131–2138 (in Chinese).

    [25] JIANG G C, LIN X C, ZHANG S J et al. Supercritical fluid extraction of direct coal liquefaction residue basing on Hansen solubility parameters [J]. Chem. J. Chinese Universities, 2015, 36 (3): 544–550 (in Chinese).

    [26] JIANG G C. Selective extraction of coal based liquid products based on the theory of solubility parameter [D]. Beijing: China University of Mining and Technology, 2015 (in Chinese).

    [27] HANSEN C M. Hansen Solubility Parameters: A User’s Handbook [M]. CRC Press, 2007.

    [28] LIU G Q, MA L X, LIU J. Chemical and Chemical Properties Data Book·Organic Volume (Upgraded) [M]. Beijing: Chemical Industry Press, 2013 (in Chinese).

    [29] JIAO Z, MA S L, WANG B et al. Correlation and prediction of liquid–liquid phase equilibrium of ionic liquid–alcohol–water systems with NRTL equation [J]. Journal of Chemical Industry and Engineering (China), 2006, 57 (12): 2801–2805 (in Chinese).

    [30] MAGNUSSEN T, RASMUSSEN P, FREDENSLUND A. UNIFAC parameter table for prediction of liquid–liquid equilibriums [J]. Industrial & Engineering Chemistry Process Design & Development, 1981, 20 (2): 331–339.

    [31] XU W L, HUANG Y B, QIAN J H et al. Studies on the solubility of stigmasterol and β-sitosterol in cyclohexanone and n-pentanol [J]. Journal of Chemical Engineering of Chinese Universities, 2003, 17 (6): 707–710 (in Chinese).

This Article


CN: 11-1946/TQ

Vol 69, No. 08, Pages 3479-3487+3293

August 2018


Article Outline


  • Introduction
  • 1 Experimental materials and methods
  • 2 Results and discussion
  • 3 Conclusions
  • Explanation of symbols
  • References