Denitrification of simulated oil by extraction with H2PO4-based ionic liquids

•[BMIM]H2PO4 and [MIMPS]H2PO4 show a high selectivity to N-compound of simulated oil.•The acidity of ionic liquids contribute denitrification.•The denitrification process was carried out in absence of any other acid or base catalyst.•[BMIM]H2PO4 and [MIMPS]H2PO4 can be reused 6 times without obvious decrease in activity.•Environmentally friendly strategy was provided for denitrification of oil.

Three dihydrogen phosphate-based (H2PO4-) ionic liquids (ILs) with different cations, i.e., 1-methylimidazolium ([HMIM]), 1-butyl-3-methylimidazolium ([BMIM]), 1-methyl-3-(3-sulfopropyl)-imidazolium ([MIMPS]), are synthesized and investigated to determine their properties on the denitrification from simulated oil that compose of quinoline and n-heptane. Experimental results show that the mechanism of denitrification is not only liquid–liquid extraction, the acidity of ILs also contribute denitrification. With the increase of acidity, ILs show a high selectivity to quinoline. When ILs ([BMIM]H2PO4, [MIMPS]H2PO4) are used, under ambient conditions: temperature is 25 °C, time is 30 min, mass ratio of IL/oil is 1:10 and IL/H2O is 2:1, the rate of denitrification can reach more than 99%. They can be recycled for 6 times without significant decrease in activity.