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Poly(ethylene glycol) Diacid-Based Deep Eutectic Solvent with Excellent Denitrogenation Performance and Distinctive Extractive Behavior

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journal contribution
posted on 04.10.2019, 12:05 by Shuang Zhu, Jiaolai Xu, Hanlin Cheng, Jiajun Gao, Xingmao Jiang, Chunxi Li, Weimin Yang
Poly­(ethylene glycol) diacid [dcPEG, HOOCCH2(OCH2CH2)nOCH2COOH] can form a deep eutectic solvent (DES) with tetraethylammonium chloride (TEACl). The dcPEG-based DES (dcPEG-250/TEACl) as extractant (Ex) showed high performance for both basic and nonbasic N-species. In n-octane model oil, N-distribution coefficient [DN, (μgN·gEx–1)/(μgN·goil–1)] can be more than 100 for both indole and pyridine. In real oils, the DES was still effective (DN > 2.0; oil yield > 96.0%). The excellent performance was due to contributions of TEACl: (1) weakening the intermolecular interaction of dcPEG; (2) releasing Lewis basic −(OCH2CH2)n–; (3) intensifying polarity of the extractant. Extractive behaviors for the both N-species can be reflected by Freundlich- or Langmuir-like relationships between equilibrium N-contents in the extractant and the oil phases, respectively. It was interesting that, from dcPEG-250 to dcPEG-250/TEACl, the behaviors significantly changed. For the nonbasic, the extraction changed from chemical behavior with H-bonding to pseudo-physical one caused by solvent polarization. For the basic, it moved away from reactive behavior and changed to the chemical one involving acid–base interaction.