Highly Efficient Separation of Phenolic Compounds from Oil Mixtures by Imidazolium-Based Dicationic Ionic Liquids via Forming Deep Eutectic Solvents

Abstract

The separation of phenolic compounds from oil mixtures is an important step for further refining or applications of the oil mixtures. In this work, three imidazolium-based dicationic ionic liquids (DILs; 1,2-bis[N-(N′-methylimidazolium)]ethane dibromide, DIL1; 1,3-bis[N-(N′-methylimidazolium)]propane dibromide, DIL2; and 1,4-bis[N-(N′methylimidazolium)]butane dibromide, DIL3) were synthesized and used to separate phenolic compounds from oil mixtures. The effects of time, temperature, DIL:phenol mole ratio, and initial phenol concentration on separation performance were investigated in detail. It was found that the removal efficiency of phenol followed the order DIL1 < DIL2 < DIL3. DIL3 showed the maximum phenol removal efficiency of 96.6% and the minimum ultimate phenol concentration of 3.9 g/dm 3 . Initial phenol concentration had little influence on the ultimate phenol concentration. Less than 0.4 in DIL:phenol mole ratio was needed to obtain the highest phenol removal efficiency, and the separation process could be completed within 5 min. These DILs could be reused without a decrease in the removal efficiency of phenol, and the properties of DILs did not change after four cycles. Also, DIL3 was demonstrated to separate phenolic compounds from real coal tar oil with the removal efficiency of 93.1%. Importantly, these DILs showed much smaller solubilities in oil mixtures than monocationic ILs. In addition, these DILs showed higher thermal stabilities than monocationic ILs, which provides a broader range of operation temperature than ever.

Systematic Synthesis and Properties Evaluation of Dicationic Ionic Liquids, and a Glance Into a Potential New Field

“…a Youan et al (2017) .b Priede et al (2014) .c Zhang et al (2018) .d Lee et al (2010) .e Yang et al (2014) .f Lee et al (2011) .…”

“…In order to obtain further information on these ionic media, which have already been used in few applications [e.g., in situ formation of DESs in an innovative procedure for the separation of phenols from oils (Youan et al, 2017, 2018), CO 2 cycloaddition reaction (Liu et al, 2015), elucidation of a reaction mechanism (Bortolini et al, 2014)] or could be used to develop stimuli responsive ionic polymers, a systematic investigation of a homogeneous class of 12 imidazolium based dicationic dibromides and related dicarboxylate salts has been performed. The thermal properties of this latter class of compounds were also compared to mono cation derivatives.…”

Cathodic Behaviour of Dicationic Imidazolium Bromides: The Role of the Spacer

“…[3] The main advantage in using DILs instead of the corresponding ILs lies in the possibility of further modulating their properties varying the nature of the spacer. [4] In fact, imidazolium DILs have been successfully used as electrolytes in dye sensitized solar cells (DSSCs), [5] as efficient replacements of organic phase-change materials (the heat capacity of DILs is noteworthy higher than that of the corresponding monocations), [6,7] as solvents for the controlled pyrolysis of cellulose, [8] as templates for the synthesis of ZnO nanostructures in water, [9,10] as surfactants (due to a better capacity of aggregation with respect to monocationic analogues), [11] as efficient extractors of phenolic compounds from oil mixtures [12] or of triazole fungicides from contaminated water, [13] etc.…”

Extraction Techniques of Phenolic Compounds from Plants

“…The results demonstrated that the antioxidants contained in the Anethum graveolens extracts were able to giving hydrogen to a free radical to eliminate potential damage. In another work, the separation of phenolic compounds from oil mixtures by three imidazoliumbased dicationic ionic liquids was investigated by Wu et al [16]. 1,4-bis[N-(N′methylimidazolium)]butane dibromide demonstrated the maximum phenol removal yield of 96.6% within 5 min.…”