Imidazolium-based zinc-containing ionic liquids (ILs), [1-R-3-R'-imidazolium]alkylsulfate-ZnCl2 (R and R' = H or alkyl), were highly effective for the denitrogenation of a model oil containing quinoline, indole, or acridine in n-heptane. Fast atom bombardment (FAB)-mass spectra and a computational study imply that the interaction of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIm]EtSO4) with ZnCl2 produces Zn-containing ILs, presumably [EMIm]ZnCl2(EtSO4) and [EMIm]ZnCl(EtSO4)(2) as the major ionic species. The interaction of EtSO4- and ZnCl2(EtSO4)(-) with a heterocyclic N compound was theoretically investigated. The zinc-containing IL, [EMIm]ZnCl2(EtSO4), used for the extraction of quinoline was successfully regenerated by employing diethyl ether as a back extractant.