Separation of phenolic compounds from oil mixtures using environmentally benign biological reagents based on Brønsted acid-Lewis base interaction

Phenolic compounds, which are widely used in producing synthetic fibers, engineering plastics, and other industrial organic chemicals, can be obtained from oil mixtures before further processing or applications by separation. Based on Lewis/Brønsted acid-base theory, we proposed the separation of phenolic compounds from oil mixtures using some environmentally benign biological reagents (BRs, including 1,3-dimethylxanthine-DMX, isonicotinamide-INA, and L-lysine-LYS). The effects of stirring time, temperature, initial phenol concentration, and BR:phenol mole ratio on phenol removal were studied in detail. LYS, INA and DMX show phenol removal efficiencies of 98.4%, 82.2%, and 66.6% from toluene at BR:phenol mole ratios of 1.6, 1.4, and 0.4, respectively, and those of 99.1%, 91.8%, and 74.6% from n-hexane at BR:phenol mole ratios of 2.20, 1.60, and 0.80, respectively, at room temperature. The BRs were regenerated with an anti-extraction method for four cycles without significant changes in separation efficiency and their properties. In addition, it is found that there is little toluene entrained in the biological reagents, which is as low as 2.3 wt% of separated phenol, indicating high purities of products. These BRs show the advantages of easy biodegradation, no corrosion to the equipment and containers, and no pollution to the environment.