High-Performance Separation of Phenolic Compounds from Coal-Based Liquid Oil by Deep Eutectic Solvents

Abstract

The separation of phenolic compounds from coal-based liquid oil is of economic value and practical significance. Conventional separation techniques for phenolic compounds always produce a large amount of wastewater. Herein, deep eutectic solvents (DESs) are considered as effective alternatives to traditional solvents. To complete the separation of phenolic compounds from coal-based liquid oil, DESs should have stronger interactions with phenols than the oil and form new DES-phenol aggregates, breaking the original molecular aggregates in the oil. Initially, density fuunctional theorycalculations were used to explore and prove the feasibility of phenolic compound separation by a choline chloride (ChCl)-glycerol DES from the perspective of interaction type and intensity, and the calculation results were verified by spectral experiments. Then, based on the phenol removal efficiency and neutral oil entrainment, the influences of the mole ratio of glycerol to ChCl, separation temperature, and DES dose were investigated and followed by discussions on the reuse of DES and a comparison of its separation capacity with that of a reported separation agent. Finally, this DES was applied to separate phenolic compounds from real coal-based liquid oil. The results show that H-bonds between the DES and phenolic compounds are the main driving force of this separation process. Under optimal conditions, the ChCl-glycerol (1:1) DES can extract 98.3% of the phenolic compounds with only 4.2% entrained neutral oil, and the selectivity is better than that of ChCl alone. Additionally, satisfactory results were obtained in the separation of phenolic compounds from real coal liquefaction oil and real coal tar, providing a universal method for the separation of phenolic compounds from coal-based liquid oil.

Separation of phenolic compounds from oil mixtures by betaine‐based deep eutectic solvents

“…Then, compared with the ionic liquid, Bet‐Gly has lower price and simpler synthesis process, and it is more suitable for industrial applications. Besides, compared with other DES that are mostly synthesized from quaternary ammonium salts containing halogen atoms, for example, choline chloride‐glycerol (extraction efficiency is 98.3%, the neutral oil entrainment is 4.2%), 33 although Bet‐Gly extraction efficiency is about 4% lower and neutral oil entrainment is similar, Bet‐Gly has no harm to steel equipment, and this is an irreplaceable advantage. Compared with the betaine that was used as solvent alone, the Bet‐Gly has a slightly larger highest extraction efficiency (94.7%) than betaine (93.0%), 29 and it reduced entrainment of neutral oil in extraction (5.2%) than betaine (14.8%) 30 .…”

Separation of m-Cresol from Coal Tar Model Oil Using Propylamine-Based Ionic Liquids: Extraction and Interaction Mechanism Exploration

“…In addition, more results of separating phenolic compounds using ILs as extractants were reported in the literature. 6 , 27 − 29 To our knowledge, m -cresol has the highest content (13.41 wt %) in phenol oil from low-temperature coal tar, 30 but fewer literature studies have reported the separation of m -cresol as a representative phenolic compound from model oil since phenol or p -cresol is usually selected as the typical phenolic compound. 6 , 21 , 31 − 33 Hence, it is meaningful to explore the separation of m -cresol from LTCT by means of ionic liquids.…”

One-step conversion of lignin-derived alkylphenols to light arenes by co-breaking of C–O and C–C bonds

“…Catalytic hydrodeoxygenation (HDO) of phenols is a crucial process in the conversion of lignin-derived bio-oils 1–4 and coal-derived oils. 5,6 Alkylphenols, as an important class of phenolic compounds, are abundant in bio-oils 1 and coal-derived oils. The alkyl groups in alkylphenols are mainly methyl, ethyl, propyl, etc.…”