A series of SO42− promoted metal oxide solid superacids: SO42−/ZrO2–WO3 (SZW), SO42−/ZrO2–MoO3 (SZM) and SO42−/ZrO2–Cr2O3 (SZC) were prepared by incorporating different metals into SO42−/ZrO2 (SZ). The above four catalysts were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction and NH3-temperature programmed desorption techniques and scanning electron microscope. Then, they were respectively used as catalysts for oxidative desulfurization for model oil under the same mild conditions. The results exhibited that catalytic activities of SZW, SZM and SZC all increased to different degrees compared with SZ. Among them SZC performed best. Finally, the possible mechanism of this reaction was also presented.

•Green synthesis of chlorobenzene with low toxicity caprolactam Brønsted acidic ionic liquids.•Investigation of the reaction conditions on the synthesis of chlorobenzene.•The reasonable explanations for improving the yield and regioselectivity.Three kinds of Brønsted acidic ionic liquids caprolactam benzenesulfonate ([CP]BSA), caprolactam hydrosulfate ([CP]HSO4) and caprolactam p-toluenesulfonate ([CP]pTSA) were synthesized. The structures of the ILs were confirmed by 1HNMR and FT-IR. Regioselective mononitration of chlorobenzene has been investigated in HNO3–Ac2Osystem with three ionic liquids. The sequence of the nitrification activity is [CP]HSO4 > [CP]pTSA > [CP]BSA. With the caprolactam hydrosulfate as the catalyst the influences of reaction time, reaction temperature and the amount of the catalyst were studied in the nitration of chlorobenzene. The results showed that the optimum reaction conditions were as follows: when the mole ratio of chlorobenzene to ionic liquid was 10:1.5, the reaction temperature was 60 °C and the reaction time was 2.5 h, the yield of mononitro-chlorobenzene could reach 71.22%. And the mass ratio of para/ortho isomer was 7.74, which was much more than 2.0 of para/ortho isomer mass ratio obtained by nitric-sulfuric mixed acids as catalyst. Besides, the ionic liquid could be used repeatedly.

The Brönsted acidic ionic liquids N-carboxymethylpyridine hydrosulphate ([CH2COOHPy][HSO4]) and N-carboxyethylpyridine hydrosulphate ([(CH2)2COOHPy][HSO4]) were synthesized and used as the extractant and catalyst for the extraction–oxidation desulfurization of model oil. The structures of the ILs were confirmed by 1H NMR and 13C NMR. The density, viscosity and acid strength of the ILs were also investigated. The acid strength was in order of H2SO4 (98%) > [CH2COOHPy][HSO4] > [(CH2)2COOHPy][HSO4]. The [CH2COOHPy][HSO4] showed better activity during the removal of dibenzothiophene (DBT) in n-octane by a combination of extraction and oxidation, and the sulfur removal reached 99.9% under the conditions of Vmodel oil = 20 mL, VIL = 1.2 mL, T = 30 °C and H2O2/S molar ratio (O/S) = 6. In the same conditions, the removal of benzothiophene (BT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) by using [CH2COOHPy][HSO4] reached 82.5% and 89.1%, respectively. Ionic liquid [CH2COOHPy][HSO4] can be recycled 9 times without a significant decrease in the sulfur removal.Graphical abstractHighlights► The extraction–oxidation desulfurization system by TSIL [CH2COOHPy][HSO4] without adding additional catalyst. ► The TSIL which was halogen-free and had high catalytic oxidative activity was synthesized and used as both extractant and catalyst. ► The TSIL showed the good recycling performance.