Highly Efficient Extraction of Phenolic Compounds from Coal Tar Using Alcohol Amine Aqueous Solutions via Synergistic Extraction

This study utilizes aqueous solutions of organic amines as extractants to remove phenolic compounds from coal tar. It elucidates the extraction mechanism between phenolic compounds and organic amines, and conducts a comprehensive investigation into the extraction performance of various monomeric organic amine aqueous solutions and their composite solutions for phenolic compounds in model oils or light coal tar. The experimental results showed that monoethanolamine (MEA), characterized by a higher reaction equilibrium constant, exhibits superior extraction performance for phenolic compounds in light coal tar compared to diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), and diethylaminoethanol (DEAE) when used at the same mass concentration of extractant. The addition of a specific concentration of DEA or TEA to a 20 wt%–25 wt% MEA solution significantly reduces the entrainment of neutral oil impurities during the extraction process and enhances the precipitation of phenolic compounds during the acidification phase. Under the optimal process parameters, the composite aqueous solution, comprising 25 wt% MEA, 5 wt% DEA, and 5 wt% TEA, demonstrated a 35.1 wt% increase in the acidification yield of phenolic compounds, Ya,P, a 20.8 wt% increase in the total yield of phenolic compounds, YP, and a 46.0% significant decrease in neutral oil entrainment compared to the solution with a 30% MEA aqueous solution.