Green and designable deep eutectic solvents for extraction separation of oxygenated compounds in Fischer-Tropsch oil products: Hydrogen bond descriptors and structure–activity study

In this work, choline fluoride, choline chloride, and 2-fluoroethyl-trimethylammonium bromide containing –F, –Cl, and –Br structures were used as hydrogen bond receptors. Acetamide, urea, trifluoroacetamide, xylitol, ethylene glycol, malonic acid and lactic acid containing –HN2, –COOH, –OH, and –F structures were used as hydrogen bond donors. We constructed functional deep eutectic solvents rich in hydrogen bond donors and acceptors while providing alcohol hydrogen bond attraction sites and aldehyde and ketone hydrogen bond attraction sites. The efficient separation and enrichment of trace alcohols, aldehydes, and ketones in Fischer-Tropsch (F-T) oil products were achieved through hydrogen bond interaction. The mechanism of selective extraction of different types of oxygenated compounds by functionalized deep eutectic solvents was revealed, and the linear relationship among structure, hydrogen bond descriptor, and extraction performance was clarified through quantum chemistry calculations. Further, liquid–liquid extraction was used to extract and separate the oxygenated compounds from high-temperature F-T oil products using the synthesized functional deep eutectic solvent. The experimental results showed that propanol, butyraldehyde, and methylethylketone could be extracted simultaneously and efficiently, and the solvent effects were consistent with the results of quantum chemistry calculation. The excellent extraction and separation effects were due to the large number of hydrogen bonds and oxyphilic atomic forces of deep eutectic solvents. The modern solvent was reasonably designed, which is significant for extracting different oxygenated compounds from high-temperature F-T oil products.