(540e) Efficient Extraction of Phenolic Compounds from Oils with Dicationic Ionic Liquids Via Forming Deep Eutectic Solvents

Efficient extraction of phenolic compounds from oils with dicationic ionic liquids via forming deep eutectic solvents

Youan Ji¹, Yucui Hou², Shuhang Ren³, Congfei Yao⁴, Weize Wu^1,*

^ 

¹State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China

²Department of Chemistry, Taiyuan Normal University, Taiyuan 030031, China

Phenolic compounds, which are widely applied in producing synthetic fibers, engineering plastics, pesticides, medicines, explosives and so on, are necessary to be extracted from oil mixtures before further applications. In this work, six dicationic ionic liquids (DILs, including 1,2-bis[N-(N’-methylimidazolium)] ethane 2Br^–, DIL1; 1,3-bis[N-(N’-methylimidazolium)] propane 2Br^–, DIL2; 1,4-bis[N-(N’-methylimidazolium)] butane 2Br^–, DIL3; N,N,N, N′,N′,N′-hexaethyl-ethane-1,2-diammonium dibromide, DIL4; N,N,N,N′,N′,N′-hexaethyl -propane-1,3-diammonium dibromide, DIL5; N,N,N,N′,N′,N′-hexaethyl-butane-1,4- diammonium dibromide, DIL6) were found and used to extract phenolic compounds from model oil and coal tar. We have studied the effect of time, temperature, DIL:phenol mole ratio, and initial phenol concentration on the extraction efficiency (EE) of phenol. It was found that the DIL:phenol mole ratio was only 0.3 or 0.4 for the highest EE of phenol. The extraction process could be finished within 5 min, and EE did not significantly change with increasing temperature. Also, the ultimate phenol concentration remained constant despite the difference in initial phenol concentrations. Of these DILs, DIL5 showed the lowest ultimate phenol concentration of 3.9 g/dm³, and EE of phenol could reach as high as 97.0%. We also reused these DILs and the results showed that these DILs could repeatedly extract phenol from model oil. In addition, EE of phenolic compounds from real coal tar using DIL5 was found to be 92.7%. The mechanism was analyzed by FT-IR, and the results showed that there was a hydrogen bond between phenol and DIL. Moreover, a comparison was made between DILs and mono-ILs. It was found that the DILs were much more thermally stable, and showed smaller solubility in oil mixtures than mono-ILs.

This work is financially supported by the National Basic Research Program of China (2011CB201303), and Specialized Research Fund for the Doctoral Program of Higher Education (20120010110005).

Keywords: Extraction; Phenolic compound; Model oil; Dicationic ionic liquid; Deep eutectic solvent