Complex Extraction of Phenol and Cresol from Model Coal Tar with Polyols, Ethanol Amines, and Ionic Liquids Thereof

To develop a greener process for reclaiming phenolic compounds from low temperature coal tar, extractive performance of twelve extractants, including mono-, di-, and triethanol amines (MEA, DEA, TEA), six protonated ionic liquids (ILs) thereof with formate (FA) or acetate (Ac) anion, choline chloride, and two polyols (glycol, glycerol), were studied at varying conditions, along with the back extractability of phenols by ether. The extraction performance is MEA > DEA > TEA ≈ ILs > glycol > glycerol, while the back extraction performance of ether is just the opposite. The coexistent toluene in oil and temperature show a little influence on the extraction performance of alcoholic amines and their corresponding ILs. The extraction performance of extractants is consistent with their complexability with phenol, i.e. ethanol amines > ether > ILs > polyols, as manifested by the red shift of the UV spectrum of phenol in the above solvents. [HMEA]FA is the most promising extractant for its overall extraction performance, cheapness, and other favorable physical attributes.