Thiophenic Sulfur Compounds Research Articles

Efficient room-temperature oxidation of dibenzothiophene over mesoporous WO3@ZrO2-TiO2 composites derived from polymer-oriented self-assembly strategy

Deep removal of thiophenic sulfur compounds in fuel oil remains an enormous challenge to achieve ultra-clean diesel production. Herein, a polyoxometalate-based inorganic-organic hybrid derived mesoporous WO3@ZrO2-TiO2 composites has been prepared by a simple polymer-oriented self-assembly strategy using polyethyleneimine (PEI) as the structure-directing agent. It exhibits that the existence of mesoporous pore channels, Zr doped TiO2 matrix, and highly dispersed WO3 active sites on the ZrO2-TiO2 framework can facilitate the adsorption-oxidation process of thiophene-type sulfide and provide more accessible active sites. The as-prepared mesoporous WO3@ZrO2-TiO2 composite shows good catalytic activity for dibenzothiophene (DBT) at room temperature, removing 500 ppm of DBT from simulated oil within 80 min, making it a suitable alternative catalyst for deep oxidative desulfurization.

Adsorptive desulfurization of thiophenic sulfur compounds using nitrogen modified graphene

In this study, nitrogen modified graphene was investigated for adsorptive desulfurization of thiophene, benzothiophene and dibenzothiophene. For these compounds, graphene (257 m2/g and 0.48 cm3/g) showed adsorptive removal of 70.1, 65.4 and 61.2%, respectively. Nitrogen modification enhanced separation of graphene layers, resulting in increase of surface area and pore volume. With increase in nitrogen content, both properties were further enhanced. The highest surface area (301 m2/g) and pore volume (1.12 cm3/g) were obtained for 14-N-GR with highest nitrogen content of 13.8 wt%. Adsorptive removal was thereby, highest for 14-N-GR, with 97.3, 92.8 and 88.4%, respectively for thiophene, benzothiophene and dibenzothiophene. The pyrrolic-N and pyridinic-N within carbon matrix contributed significantly to π-π interactions between carbon matrix and sulfur compounds. The order of adsorptive removal efficiency for sulfur compounds was also associated with their molecular size. The adsorptive desulfurization was best described by pseudo-second-order kinetics and best represented by Langmuir adsorption model. The monolayer model agreed with major contribution of π-π interactions between adsorbate and adsorbent surface. The spent adsorbents regenerated using thermal process showed cyclic and thermal stability. After five adsorption-regeneration cycles, percentage removal decreased only up to 14%, without any major morphological change of adsorbent.

Enhanced adsorptive removal of thiophenic sulfur compounds by nitrogen-doped surfactant modified mesoporous templated carbons

Adsorptive desulfurization is a greenway for sulfur removal from fossil fuels due to its ambient operating conditions and easy recyclable usage of spent adsorbent. This paper studied the effect of nitrogen doping in mesoporous templated carbon for the adsorptive removal of sulfur compounds from model fuel. The undoped and nitrogen-doped templated carbons were synthesized using alumina and surfactant-modified alumina as templates via the chemical vapor deposition method. Modification by nitrogen enhanced both the surface area and pore volume of templated carbon. The nitrogen-doped surfactant-modified alumina templated carbon, AS-N, showed the highest surface area of 1373 m2/g and pore volume of 1.15 cm3/g. The AS-N showed adsorptive removal of sulfur compounds (thiophene 92.15%, benzothiophene 82.90% and dibenzothiophene 82.38%) at 70 °C. This may be attributed to the highest surface area and presence of nitrogen (8.2 wt%), which improved the adsorption capability by increasing the π-π interaction between the sulfur compounds and carbon matrix. Further increase in nitrogen content in templated carbon enhanced the π-π interaction resulting in higher removal capacity. The AS-N-U adsorbent prepared in the presence of urea had 15.2 wt% nitrogen and showed enhanced removal of thiophene 97.7%, benzothiophene 92.4%, and dibenzothiophene 89.3%. The adsorptive desulfurization over AS-N-U for all sulfur compounds were best fitted to pseudo-second order kinetic model and Langmuir adsorption isotherm model. The templated carbon was regenerated successfully using the thermal regeneration process. After five adsorption-regeneration cycles, the removal efficiency was lowered only by 4–10% for all sulfur compounds.

Intraparticle ripening to create hierarchically porous Ti-MOF single crystals for deep oxidative desulfurization.

The catalytic oxidative desulfurization (ODS) technique is able to remove sulfur compounds from fuels, conducive to achieving deep desulfurization for the good of the ecological environment. Ti-based metal-organic frameworks (Ti-MOFs) possessing good affinity to organic reactants and considerable numbers of Ti active sites are promising catalysts for ODS. However, current Ti-MOFs suffer from severe diffusion limitations caused by the size mismatch between sole micropores and bulky sulfur compounds, leading to poor ODS performance. Here, a facile method of intraparticle ripening without any additive is developed to obtain hierarchically meso-microporous Ti-MIL-125 single crystals (Meso-Ti-MIL-125) for the first time. Such Meso-Ti-MIL-125 shows a BET surface area of 1401 m2 g-1 and a mesoporous volume that is 1.7 times as high as that of the conventional Ti-MIL-125. Our novel Meso-Ti-MIL-125 exhibits excellent catalytic performance in the ODS of a series of bulky thiophenic sulfur compounds, completely removing benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (DMDBT) from model fuels, which is, respectively, 2.4 times, 1.5 times, and 6.7 times higher than the removal achieved with conventional Ti-MIL-125. Such a facile synthetic strategy is envisioned to be applied in many kinds of crystalline materials, such as zeolites, for industrial production.

Boosting the Adsorption Performance of Thiophenic Sulfur Compounds with a Multimetallic Dual Metal-Organic Framework Composite.

Adsorptive desulfurization over metal-organic frameworks (MOFs) remains a challenge in maintaining good performance in the presence of water. Herein, multimetallic Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) is first achieved through phase-competition-driven growth technology. The adsorption performance of thiophene (Th), benzothiophene (BT), and dibenzothiophene (DBT) in model fuels is systematically investigated at mild temperature and follows the order Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) > MOF-5 > MIL-88B. Excellent adsorptive activity is mainly ascribed to the associative effects of multimetal active sites, suitable pore sizes and shapes, acid-base interactions, and complexation. Meanwhile, MIL-88B exhibits a "brick-wall" effect and effectively enhances the water stability of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) more than does MOF-5. Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) exhibits superior stability even after being immersed in water for 5 days, maintaining 77, 77, and 81% of the initial DBT, BT, and Th uptake capacities. After five periods of regeneration, more than 90% of the desulfurization capacity of Fe/Ni/Cu/Zn-(MIL-88B)-on-(MOF-5) was recovered. This work provides a new strategy for the synthesis of desirable MOF-on-MOF, promoting its potential application to adsorption desulfurization.

Enhanced Adsorptive Removal of Thiophenic Sulfur Compounds by Nitrogen-Doped Surfactant Modified Mesoporous Templated Carbons

Enhanced Adsorptive Removal of Thiophenic Sulfur Compounds by Nitrogen-Doped Surfactant Modified Mesoporous Templated Carbons

Upgrading of thiophenic compounds from fuels over a silver-modified MoO3 catalyst under ambient conditions

The demand for heterocyclic sulfur compounds is increasingly in fine chemical industry, where the thiophenic sulfur impurities in fuels can be a potential recyclable feedstock. In this work, the catalytic upgrading of thiophenic sulfur compounds over a silver-modified MoO3 catalyst under ambient conditions was reported. Br2 and H2O2/HBr were used to convert thiophenic compounds in alkane and alcohol solutions. The conversion of various thiophenic compounds (thiophene, benzothiophene and dibenzothiophene) to the corresponding bromides reached up to 81.6 ~ 99.8%. The bromination path undergoes electrophilic substitution mechanism, and the transformation of mono- to dibromides is identified as the rate-determining step. The introduction of MoAg2O4 phase on MoO3 is rationalized to boost the conversion of mono-bromothiophene, which results in the selectivity of 2,5-dibromothiophene increased from 10% to over 50%. The optimized silver loading was 10% due to its high thiophene conversion and selectivity of dibromides. Silver modification of MoO3 rods not only stabilized the textural property of catalysts but also improved its bromination activity compared to the bulk MoO3 indicated by SEM and FTIR characterization. Density functional theory (DFT) calculation suggested that the formation of 2-bromothiphene and 2,5-dibromothiophene were preferred on the MoO3(111) and MoAg2O4(111) sites, respectively. The catalytic upgrading approach paves the way for the efficient utilization of thiophenic sulfur impurities in fuels to their value-added under mild conditions.

Metal-free aerobic oxidative desulfurization over a diethyltriamine-functionalized aromatic porous polymer

A new cross-linked aromatic porous polymer (CAPP) from bifonazole and 4,4′-bis(bromomethyl)biphenyl was prepared and functionalized with diethyltriamine (DETA). The product CAPP-DETA was applied as a catalyst for the removal of thiophenic sulfur compounds via oxidative desulfurization: 100% conversion of dibenzothiophene (DBT) was achieved with 50 mg of CAPP-DETA for 400 ppm DBT in decane at 120 °C after 4 h using O2 as the oxidant. The reaction was carried out under different reaction conditions of temperature (80 to 140 °C), catalyst amount (10 to 50 mg), and concentration (200 to 1000 ppm). Radical scavenger experiments indicated the reaction involving the triamine functionality in the catalyst generating the superoxide (O2•-) radicals. The conversion efficiency among the thiophenic compounds followed a sequence of dibenzothiophene > benzothiophene > thiophene. The catalyst was reusable for four repetitive cycles without deterioration in catalytic activity.

Deep removal of thiophene and benzothiophene in low-sulfur fuels over the efficient CeAlSBA-15 adsorbent synthesized by sequential alumination and cerium incorporation

Deep removal of thiophenic sulfur compounds in the low-sulfur concentration fuels (e.g., < 50 μg/g S) has been facing a great challenge. Ce-containing adsorbents as a typical representation of “S-M” bonding mechanism have performed an excellent adsorption selectivity, while it cannot be unsatisfactory for the sulfur capacity due to the ambiguous and complexity of effective adsorption active sites. Herein, we aim to address the above difficulty, employing the CeAlSBA-15 materials that are synthesized for the first time by the sequential alumination and Ce incorporation. The data results of XRD, Ar adsorption, TEM and EDX mapping indicate that the Ce species can be highly dispersed onto the micro-mesoporous surface of CeAlSBA-15 by the induction of Al species. Moreover, the UV–vis, XPS and in situ FTIR spectra further reveal that the isolated Ce(III) species (e.g., -Al-O-Ce-O-Si-) located onto the CeAlSBA-15 adsorbents can be considered as effective adsorption active sites, rather than the Ce(IV) species (e.g., -Ce-O2-Ce-) that is difficult to be touched due to the steric hindrance. For the model fuels of thiophene and benzothiophene, 90 and 65 mL/g of sulfur-free fuels can be produced by using the CeAlSBA-15(NH4+) adsorbent, respectively, which are much superior to the best one reported. In particular, the adsorbent shows an excellent regeneration performance after three cycles (90.8% sulfur capacity recovered), and also can perform an outstanding adsorption selectivity (36.7%) in the presence of 5 wt% benzene. The contribution of this work can pave a way for further developing more excellent desulfurization adsorbents with effective adsorption active sites.

Facile fabrication of a superior Cu(I)-NH4Y zeolite adsorbent for improving thiophene adsorption selectivity in the presence of aromatics or olefins

Cu modified Y zeolite adsorbents have performed excellent adsorption desulfurization performance. Adsorption selectivity of thiophenic sulfur compounds, however, still remained a lower level in the presence of aromatics and olefins. In this work, we aim to address the above challenge, using Cu(I)-NH4Y zeolites obtained by liquid phase ion-exchanged method. Based on the coordination chemistry theory, the new adsorption active sites ([Cu+···NH3···H+] species) can be facilely fabricated at lower temperature (ca. 150 °C) and under H2 atmosphere. The desulfurization experimental results indicate that the outstanding breakthrough sulfur capacity (ca. 31.0 mg (S) · g−1) can be achieved by the Cu(I)0.10-NH4Y adsorbent, which is about 2.3 folds as high as the best one reported. After regeneration with three cycles, the adsorbent still remains a high sulfur capacity. Importantly, the thiophene adsorption selectivities of adsorbent have been improved in the presence of aromatics or olefins, which are about 44.5% and 6.3%, respectively. Meanwhile, the direct “S-M” bonding mechanism between thiophene and [Cu+···NH3···H+] species can be really proposed. Besides, the alkylation reaction between thiophene and olefins is significantly attenuated, mainly ascribed to the majority of strong Brønsted acid sites being masked. The new design idea of effective active sites in the zeolite adsorbents breaks out the traditional high-temperature preparation concept of excellent desulfurization adsorbents and can provide a new direction in the future.

Enhancing oxidation resistance of Cu(I) by tailoring microenvironment in zeolites for efficient adsorptive desulfurization

The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. However, its application is seriously hindered by the instability of Cu(I), which is easily oxidized to Cu(II) even under atmospheric environment due to the coexistence of moisture and oxygen. Here, we report the adjustment of zeolite microenvironment from hydrophilic to superhydrophobic status by coating polydimethylsiloxane (yielding Cu(I)Y@P), which isolates moisture entering the pores and subsequently stabilizes Cu(I) despite the presence of oxygen. Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere for 6 months, while almost all Cu(I) is oxidized to Cu(II) in Cu(I)Y for only 2 weeks. The optimized Cu(I)Y@P material after moisture exposure can remove 532 μmol g−1 of thiophene and is much superior to Cu(I)Y (116 μmol g−1), regardless of similar uptakes for unexposed adsorbents. Remarkably, Cu(I)Y@P shows excellent adsorption capacity of desulfurization for water-containing model fuel.

Metal-free oxidative desulfurization over a microporous triazine polymer catalyst under ambient conditions

A metal-free microporous triazine polymer (MCTP) was applied as a heterogeneous catalyst for the oxidative desulfurization (ODS) of thiophenic sulfur compounds in decane as a model fuel. Using a molecular oxygen (O2)/aldehyde system as the oxidant, complete removal of dibenzothiophene (DBT) from a 400 ppm DBT solution (10 mL) was achieved at room temperature in 15 min with 2 mmol of isobutyraldehyde (IBA). The highly efficient conversion of the DBT was explained by the formation of an acyl radical from IBA aided by the MCTP catalyst, which was converted to a peroxyacid that oxidized the DBT to DBT sulfone. The conversion efficiency of thiophenic compounds followed the sequence of electron densities in the individual S atoms: DBT > benzothiophene > thiophene. The MCTP catalyst could be reused for ODS for at least five consecutive runs without any reduction in the catalytic performance after a simple acetone wash.

Gas adsorptive desulfurization of thiophene by spent coffee grounds-derived carbon optimized by response surface methodology: Isotherms and kinetics evaluation

Abstract The elimination of sulfur compounds in the FCC gasoline is indispensable to protect downstream equipment. Researchers are trying to find technological innovations to produce the famous “zero sulfur” fuel. Many adsorbents, such as spent coffee grounds-derived carbon (SCG-AC), have been claimed to be effective in H2S removal. However, no study has been conducted to exploit its ability to eliminate the organo-sulfur compounds present in FCC gasoline such as thiophene. This work involves the optimization by the response surface methodology (RSM) of different operating conditions of activated carbon (AC) production by the chemical activation (H3PO4) of SCG. RSM was used to estimate the variables considered in the preparation of AC using the Box–Behnken Design (BBD). The optimized SCG-AC was used for the adsorption of thiophene through batch tests at ambient conditions. The equilibrium experimental data of the thiophene adsorption were analyzed by Langmuir, Freundlich, and Langmuir–Freundlich isotherms. The adsorption isotherm data fit the Langmuir–Freundlich isotherm where the adsorption’s kinetics were described by the Elovich model. The optimum SCG-AC exhibited the highest adsorption capacity, with up to 2.23 mmol/g. These results revealed that SCG-AC is a promising and economical adsorbent for the elimination of thiophenic sulfur compounds.

Separation and characterization of squalene and carotenoids derived sulfides in a low mature crude oil

An unusual distribution on molecular composition of organic sulfur compounds (OSCs) was found in a crude oil from the Bohai Bay Basin (China) that contains negligible thiophenic sulfur compounds but abundant in C30 and C40 sulfides. The sulfides were separated from the crude oil by methylation/demethylation method and characterized by gas chromatography-mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A novel series of C30 OSCs that possess a bio-precursor of squalene were identified. The lexene (C33) derived OSC was also identified for the first time in the crude oil, which indicates a strictly anaerobic condition during the early diagenesis of the source rock. Most C40 sulfur compounds were verified to be sulfides having a β-carotane skeleton. Most identified sulfides possess a thiolane group with a quaternary carbon atom or a thiane group within their carbon skeletons.

Hierarchical porous HPW/titania–silica material with superior adsorption-catalytic oxidation activity for multi-ring thiophenic sulfur compounds

HPW/titania–silica catalysts with micro-meso-macroporous structures and high specific surface areas are prepared and applied as oxidative desulfurization catalysts.

Cu, Zn-embedded MOF-derived bimetallic porous carbon for adsorption desulfurization

In this work, a metal organic framework (MOF)-restricted high-temperature carbonization autoreduction strategy was employed for the preparation of Cu, Zn-embedded porous carbon (marked as CuZn@C) via carbonizing a ZIF-8 pre-grown on CuO nanosheets. Resulting Cu(I) sites reduced from Cu(II) by using the method were homogeneously dispersed and embedded in the carbon matrix derived from the ZIF-8, which effectively formed π-complexation with thiophenic sulfur compounds, facilitating the improvement of adsorption desulfurization (ADS) performances. Accordingly, the obtained CuZn@C-0.05, provided with good porous structures, high surface area, large pore volume and uniformly distributed bimetallic active sites, exhibited a remarkable adsorption capacity of DBT (60 mg g−1). In addition, pseudo-second-order kinetic and Langmuir models presented best fitting results for DBT adsorbing on the adsorbent CuZn@C-0.05. Simultaneously, the adsorbent also revealed excellent reusability with the slight decrement of 8.4 mg g−1 after the fifth recycle, further indicating its great potential as a high-efficient and stable adsorbent for ADS.

Isolation and characterization of sulfur compounds in a lacustrine crude oil

A high-sulfur (4.69 wt%) crude oil was discovered in the China Bohai Bay Basin which is known to contain low sulfur crude oil. The composition of this high sulfur crude oil and its geological origin are unknown. In this study, thiophenic and sulfidic sulfur compounds were isolated from the crude oil by methylation/demethylation and characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography-mass spectrometry (GC–MS). Relatively high abundance of sulfur compounds with 30 carbon atoms and 5–7 double bond equivalence (DBE), which were assigned to sulfurated steranes with thiophene or tetrahydrothiophene moieties. Some of these compounds have not been reported in fossil fuels. In addition to commonly found sulfur compounds in petroleum feedstock, such as benzothiophenes and dibenzothiophenes, other structural sulfur compound types were detected: long-chain 2,5-di-n-alkylthiolanes, 2,5-di-n-alkylthianes, bicyclic terpenoid sulfides, isoprenoid thiophenes, and isoprenoid benzothiophenes. The presence of abundant biomarker sulfur compounds suggests that the sulfuration of the high sulfur crude oil was occurred in the early diagenesis stage instead of a thermochemical sulphate reduction (TSR) process.

Ultra-deep adsorptive removal of thiophenic sulfur compounds from FCC gasoline over the specific active sites of CeHY zeolite

Abstract Adsorption desulfurization performance of NaY, HY and CeHY zeolites is evaluated in a miniature fixed-bed flow by model gasoline containing with thiophene, tetrahydrothiophene, 2-methylthiophene, benzothiophene or mixed sulfur compounds. The structural properties of adsorbents are characterized by XRD, N2-adsorption and XPS techniques. Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work, have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules. Desulfurization experimental results show that the CeHY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound, especially in the capture of aromatic 2-methylthiophene (about ca. 28.6 mgS/gadsorbent). The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity, mainly resulting from the synergy between Bronsted acid sites and Ce(III) hydroxylated species active sites located in the supercages of CeHY. Meanwhile, the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites. By contrast, the oligomerization reaction of benzothiophene molecules on the active sites of CeHY cannot occur due to the restriction of cavity size of supercages, but they can be adsorbed on the Bronsted acid sites via protonation, and on Ce(III) hydroxylated species and extra-framework aluminum hydroxyls species via direct “S-M” bonding interaction. As to the tetrahydrothiophene, adsorption mechanism is similar to that of benzothiophene, except in the absence of protonation. The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.

Combining the Photocatalysis and Absorption Properties of Core-Shell Cu-BTC@TiO₂ Microspheres: Highly Efficient Desulfurization of Thiophenic Compounds from Fuel.

A core-shell Cu-benzene-1,3,5-tricarboxylic acid (Cu-BTC)@TiO2 was successfully synthesized for photocatalysis-assisted adsorptive desulfurization to improve adsorptive desulfurization (ADS) performance. Under ultraviolet (UV) light irradiation, the TiO2 shell on the surface of Cu-BTC achieved photocatalytic oxidation of thiophenic S-compounds, and the Cu-BTC core adsorbed the oxidation products (sulfoxides and sulfones). The photocatalyst and adsorbent were combined using a distinct core-shell structure. The morphology and structure of the fabricated Cu-BTC@TiO2 microspheres were verified by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, X-ray powder diffraction, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy analyses. A potential formation mechanism of Cu-BTC@TiO2 is proposed based on complementary experiments. The sulfur removal efficiency of the microspheres was evaluated by selective adsorption of benzothiophene (BT) and dibenzothiophene (DBT) from a model fuel with a sulfur concentration of 1000 ppmw. Within a reaction time of 20 min, the BT and DBT conversion reached 86% and 95%, respectively, and achieved ADS capacities of 63.76 and 59.39 mg/g, respectively. The BT conversion and DBT conversion obtained using Cu-BTC@TiO2 was 6.5 and 4.6 times higher, respectively, than that obtained using Cu-BTC. A desulfurization mechanism was proposed, the interaction between thiophenic sulfur compounds and Cu-BTC@TiO2 microspheres was discussed, and the kinetic behavior was analyzed.

A combination desulfurization method for diesel fuel: Oxidation by ionic liquid with extraction by solvent

Ionic liquids (ILs) are intensively studied in the oxidative desulfurization of diesel fuel, where ILs act as both extractants and catalysts with adding another oxidant such as H2O2 solution. Some thiophenic sulfur compounds can be effectively removed from some model diesel fuels with this method, while it is hard to reduce the sulfur content to a desirable level like less than 10 ppm with this method when people investigated the real diesel fuels. In this work, we developed a new combination desulfurization method, first oxidative desulfurization by ILs as both extractants and catalysts with 30 w% H2O2 as oxidant, then followed by desulfurization by solvent extraction. Four ILs and ten solvents were investigated for real diesel fuels. The effects of different factors on desulfurization performance were systematically studied, e.g., ILs species, solvents species, temperature, time, IL/oil mass ratio, extractant/oil mass ratio, multiple desulfurization, regeneration of ILs and solvents. The results show such a combination method is effective to reduce the sulfur content in real diesel fuels to a desirable level, e.g., the sulfur content in FCC diesel fuel was reduced to 8.1 ppm from original 150 ppm after one step oxidation by [(CH2)4SO3HMIm][Tos] (ILs/oil mass ratio of 1/2; 3 h, 348.15 K, O/S molar ratio of 40/1) and two-step extraction by DMF (extractant/oil mass ratio 1/2, 30 min, 298.15 K). ILs and solvents can be regenerated and recycled with negligible activity loss.