Removal of Thiophene and Its Derivatives from Model Gasoline

Article pubs.acs.org/IECR

Removal of Thiophene and Its Derivatives from Model Gasoline Using Polymer-Supported Metal Chlorides Ionic Liquid Moieties Xiaomeng Wang,† Hui Wan,† Mingjuan Han,‡ Lei Gao,† and Guofeng Guan*,† †

College of Chemistry and Chemical Engineering, and ‡College of Sciences, Nanjing University of Technology, Nanjing 210009, China ABSTRACT: A series of polymer-supported metal chlorides imidazolium ionic liquid (IL) moieties, M/CMPS-Im(Cl) (M = CuCl, ZnCl2 and FeCl3), were synthesized by grafted method using chloromethylated polystyrene (CMPS) resin as support. Meanwhile, the structures of synthesized ILs were characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results showed that the surface of CMPS resin was covered with a thin layer of extraction activity components. Then, the synthesized CMPS-supported imidazolium-based ILs were investigated to extract thiophene and its derivatives from model gasoline (n-octane/thiophene) under certain conditions. For a given imidazolium-based IL: first, the order of extraction capacity of extractant was CuCl/CMPS-Im(Cl) > ZnCl2/CMPS-Im(Cl) > FeCl3/CMPS-Im(Cl); the reason for this was that the π-complexation capability between Cu+ and thiophene was stronger than those of Fe3+ and Zn2+. Second, the sulfur removal selectivity of sulfur compound followed the order of TS < BT < DBT under the same conditions; it indicated that the extraction was favored for those aromatic heterocyclic sulfur compounds with higher density aromatic π-electrons density. Meanwhile, the effect of mass ratio of model gasoline to M/CMPS-Im(Cl) ILs, different initial sulfur concentrations, and extraction time on desulfurization rates of M/CMPS-Im (Cl) ILs was performed, respectively. Finally, regeneration of M/CMPS-Im(Cl) ILs was investigated. ation13−22 and denitrogenation23 processes of gasoline employing ILs have been extensively investigated. The studies indicated that the ILs had higher extraction ratios and greater selectivity in comparison with the conventional molecular solvents. However, the higher viscosity and cost of ILs restricted their industrial application. In order to overcome this problem, IL moieties were considered to immobilize on solid supports. Polystyrene (PS)-supported IL catalysts for a series of nucleophilic substitution reactions had been developed by Kim in 2004.24 Then the catalytic reaction process employing PS-supported IL catalysts had been investigated by other workers.25−27 All the reports showed that PS-supported IL catalysts were the most potential and powerful materials in the catalytic process due to their higher catalyst efficiencies and easy separation. On the other hand, it was well-known that Lewis acidic ILs with metal halide anions based on AlCl3,20 FeCl3,21 and CuCl22 were shown to exhibit promising performances on the selective removal of aromatic sulfur compounds. Also, imidazolium (Im) ILs could be immobilized on solid support by covalent bond to form imidazolium chloride functionality extractants.28 Being motivated by these expectations mentioned above, in this article, we emphasize immobilizing imidazolium ILs and Mbased imidazolium ILs (M = CuCl, ZnCl2, and FeCl3) on chloromethylated polystyrene (CMPS) resin by grafted method, denoted as CMPS-Im(Cl) and M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILs, respectively. Then, the

1. INTRODUCTION In recent years, considerable attention has been focused on deep desulfurization of gasoline and diesel due to the higher regulations on the sulfur compounds content level in fuels. Sulfur oxides caused by exhaust gases, such as SOx, were the main reason for acid rain, global warming effect, and air pollution. Many countries, including Europe and Japan, were striving to reduce the sulfur content in gasoline to less than 10 ppm by 2010.1 Industrially, the removal of simple small molecular organic sulfides in fuel oils, such as mercaptane, thioether, and so on, could be realized by means of the catalytic hydrodesulfurization (HDS) technique. However, a challenging task arose with the elimination of aromatic sulfur compounds such as thiophene or dibenzothiophene and their alkyl derivatives by use of the HDS method since it required both high temperatures (>300 °C) and high pressures (>4 MPa).2 It was well-known that this method for deep desulfurization of gasoline and diesel was a very complex problem for the petroleum industry, but the behavior of minimizing the pollution from exhaust gas of fuel oils was necessary and urgent within the required sulfur compounds content level. Then, nonhydride desulfurization technologies, including adsorption,3,4 biodesulfurization,5 oxidation,6 and extractive desulfurization,7 were developed. Ionic liquids (ILs), organic salts with melting points around or below ambient temperature, had been used as “green solvents” in a range of fundamental research and applications, including catalysis,8 synthesis,9 and separations,10 owing to their unique and useful properties, such as negligible vapor pressure, high chemical and thermal stabilities, and excellent solubility.11 The extractive desulfurization of diesel oil using a series of ILs was reported by Jess et al.12 in 2001. Extractive desulfur© 2012 American Chemical Society

Received: Revised: Accepted: Published: 3418

August 29, 2011 January 29, 2012 January 30, 2012 January 30, 2012 dx.doi.org/10.1021/ie201931a | Ind. Eng. Chem. Res. 2012, 51, 3418−3424

Industrial & Engineering Chemistry Research

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impurities. Finally, the product was dried in vacuum at 50 °C for 24 h. 2.3. Preparation of CMPS-Im(Cl). The synthetic process of CMPS-Im(Cl) is shown in Scheme 2. The immobilization of

properties of extractants were characterized by FTIR, XPS, and SEM techniques. Desulfurization properties of chloromethylated polystyrene (CMPS), CMPS-Im(Cl), and M/CMPSIm(Cl) ILs were investigated under certain conditions. Finally, the desulfurization rates of regenerated extractants were discussed as well.

Scheme 2. Immobilization of N-Methylimidazole onto CMPS

2. EXPERIMENTAL SECTION 2.1. Materials. Divinylbenzene (DVB, mixtures of isomers, 78−80% grade, Kehua Laboratory Instruments Sales Department, China) and styrene (St, >99%, Sinopharm Chemical Reagent Co. Ltd. China) were extracted with 5% (w/w) hydroxyl sodium solution to remove the inhibitor (p-hydroquinone), respectively, and then washed with deionized water until the pH was equal to 7.0. Vinyl benzyl chloride (VBC, 95%, mixtures of m- and p-isomers, Changzhou Wujin Linchuan Chem. Co. Ltd., China), 2,2-azobisisobutyronitrile (AIBN, Shanghai NO.4 Reagent & H.V. Chem. Co. Ltd.), CuCl (analytical grade, Sinopharm Chemical Reagent Co. Ltd. China), FeCl3 (analytical grade, Sinopharm Chemical Reagent Co. Ltd. China), ZnCl2 (analytical grade, Sinopharm Chemical Reagent Co. Ltd. China), poly(vinyl alcohol) (PVA, degree of polymerization: 1788), N-methylimidazole (purity, ≥98%), noctane (chemical grade), thiophene (≥99%, Alfa Aesar), benzothiophene (Aladdin), dibenzothiophene (Aladdin), and other corresponding chemicals were commercially available and used without further purification. Real oil was from Yangzi Petrochemical Company Ltd. 2.2. Preparation of Chloromethylated Polystyrene. The chloromethylated polystyrene (CMPS) beads were prepared by conventional free radical suspension polymerization according to the previous reports.29,30 The synthetic process is shown in Scheme 1. First, 3.5 g of PVA (1.0 wt %),

N-methylimidazole onto CMPS is briefly described as follows.28 In a 250 mL three-necked flask with a reflux condenser and mechanical stirring, 10 g of CMPS previously prepared was reacted with 1.0 equiv of N-methylimidazole in 60 mL of toluene at 85 °C for 24 h. The hot suspension was then filtered on a buchner funnel and washed with 20 mL of toluene and 20 mL of acetone three times, respectively. Finally, the product denoted as CMPS-Im(Cl) was dried in vacuum at 50 °C for 24 h. 2.4. Preparation of M/CMPS-Im(Cl) ILs. The synthetic processes of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) are shown in Scheme 3. CMPS-Im(Cl) (3.5 g) and metal Scheme 3. Immobilization of Metal Chlorides on the CMPSIm(Cl)

Scheme 1. Synthesis of Chloromethylated Polystyrene (CMPS)

chloride (3.5 g) were added into a 250 mL round-bottom flask, and the mixture was stirred at 80 °C for 12 h under N2 atmosphere. Ethanol was used as solvent for the synthesis of M/CMPS-Im(Cl) (M = ZnCl2 and FeCl3), and dimethylsulfoxide was used as solvent for the synthesis of CuCl/CMPSIm(Cl). The solid was recovered by filtration and washed with ethanol and methanol, respectively, and dried in vacuum at room temperature. 2.5. Preparation of Model Gasoline. The model gasoline was composed of thiophene and noctane. Thiophene (0.6342 g) was weighed accurately and added into a 250 mL volumetric flask, and then n-octane was added into the above volumetric flask until the volume was determined to be 250 mL. It showed that the concentration of thiophene was 2.5368 g/L (1381 ppm) in model gasoline. 2.6. Extractive Desulfurization Process. All of the extractive desulfurization experiments were conducted in a 20 mL stoppered test tube. Extractants were added into the model gasoline and vibrated for different time at 30 °C to reach

10.5 g of sodium chloride, and 1.75 g of AIBN (0.5 wt % of total water phase) were charged into a 500 mL three-necked glass reactor containing 350.0 mL of deionized water and stirred to obtain a transparent solution by motor stirrer. Then, 20.0 mL of the monomer mixtures (VBC:DVB:St = 12:4:4) together with 24.0 mL of porogen (Vtoluene:Vcyclohexanol = 1:1) were placed into the beaker and stirred regularly until the organic phase became uniform. The polymerization of conventional free radical suspension was conducted by adding the uniformed organic phase into the transparent solution mentioned above at 75 °C for 8 h under the protection of nitrogen. After polymerization, the resulting beads were collected by pumping filtration and washed three times with hot water and methanol in turn to remove the dispersant. Then, the product was extracted with dichloromethane for 10 h in a Soxhlet to remove the porogen and residual monomers and washed with ethanol twice to ensure the complete removal of 3419

dx.doi.org/10.1021/ie201931a | Ind. Eng. Chem. Res. 2012, 51, 3418−3424


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1b and three new peaks at 1637, 1634, and 1646 cm−1 in parts c, d, and e of Figure 1, respectively, which could be ascribed to the complexation between imidazole ring and metal ions.34,35 The phenomenon indicated that metal chlorides had been supported on CMPS-Im(Cl) particles. 3.2. XPS. XPS patterns of samples CuCl/CMPS-Im(Cl) (a), ZnCl2/CMPS-Im(Cl) (b), and FeCl3/CMPS-Im(Cl) (c) are shown in Figure 2. The characteristic peaks around 920−970,

extraction equilibrium. Then they were settled for 5 min to obtain phase splitting. 2.7. Characterization. Fourier transform infrared (FT-IR) spectroscopy was carried out on a Thermo Nicolet 870 spectrophotometer with anhydrous KBr as standard (Nicolet, U.S.). XPS patterns of samples M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) were collected on a ESCALAB250 (Thermo Electron Co.) X-ray photoelectron spectrometer, with MgKa target (1253.6 eV) as the X-ray source, passing energy of 187.0 eV, and the binding energy corrected by 284.6 eV of the Cls. Average diameters and surface morphology of CMPS and CuCl/CMPS-Im(Cl) beads were characterized by a scanning electron microscope (SEM) QUANTA200 (FEI, Holland). 2.8. Analysis of Sulfur Content. After the extraction, the oil was withdrawn. The sulfur contents of thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), and real oil were analyzed by GC-flame photometric detector (GC-FPD) with SE-54 capillary column (30 m × 0.32 mm inner diameter × 1.0 μm film thickness).

3. RESULTS AND DISCUSSION 3.1. FT-IR. FT-IR spectra of CMPS (a), CMPS-Im(Cl) (b), CuCl/CMPS-Im(Cl) (c), FeCl3/CMPS-Im(Cl) (d), and ZnCl2/CMPS-Im(Cl) (e) are shown in Figure 1. In Figure

Figure 1. Comparisons of FT-IR spectra of CMPS (a), CMPS-Im(Cl) (b), CuCl/CMPS-Im(Cl) (c), FeCl3/CMPS-Im(Cl) (d), and ZnCl2/ CMPS-Im(Cl) (e) particles.

1a and b, the characteristic peaks of polystyrene around 1492, 1599, 2850, 3025, and 2924 cm−1 could be clearly observed, which were ascribed to the characterization peaks of C−C skeleton vibration of aromatic ring, C−H asymmetric and symmetric stretching vibrations of methylene, and C−H stretching vibration of aromatic ring.31 Moreover, it could be observed that a typical peak at 1264 cm−1 corresponding to the stretching frequency of functional group CH2Cl of CMPS obviously appeared in Figure 1a and disappeared in Figure 1b. Furthermore, in Figure 1b, two characteristic peaks appeared at the positions of 1565 and 3145 cm−1, which were attributed to the CN, and CH stretching vibrations of imidazole ring.32,33 All of these results indicated that N-methylimidazole had been supported onto the surfaces of CMPS beads. Meanwhile, it could observed that the CN stretching frequency of imidazole ring shifted to higher frequencies from the comparison between the peak at 1565 cm−1 in Figure

Figure 2. XPS patterns of CuCl/CMPS-Im(Cl) (a), ZnCl2/CMPSIm(Cl) (b), and FeCl3/CMPS-Im(Cl) (c) particles.

1020, and 710 eV correspond to the existence of Cu+ and Cu2+, Zn2+, and Fe3+, respectively, which showed that metal ions had been immobilized onto CMPS-Im(Cl) particles. In Figure 2a, the Cu ion had two different valence states (Cu+ and Cu2+), which were ascribed to a small quantity of Cu+ that was 3420



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oxidized to Cu2+ during the synthetic process of the CuCl/ CMPS-Im(Cl) sample. 3.3. SEM. SEM was performed to characterize the morphology of CMPS and CuCl/CMPS-Im(Cl) particles, as shown in Figure 3. It was confirmed that CMPS and CuCl/

Table 1. Desulfurization Rates of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILsa desulfurization rate (%)

entry

S-compound

CuCl/CMPSIm(Cl)

1 2 3 4

thiophene benzothiophene dibenzothiophene real oil

68.62 74.70 77.12 72.41

ZnCl2/ CMPSIm(Cl)

FeCl3/CMPSIm(Cl)

55.01 56.64 60.27 53.16

51.26 54.84 58.63 50.28

. a

Note: mass ratio of model gasoline to extractant 5:1; extraction time 8 h; extraction temperature 30 °C.

different M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILs had the same order of DBT > BT > TS. It could be traced back to the calculation performed by Otsuki et al.,6 which was that the electron density on the sulfur atoms was 5.758 for DBT, 5.739 for BT, and 5.696 for TS, and this difference might further cause the relatively large differences of the sulfur compound partition coefficients. We also could trace back to the investigation of using a series of ILs to extract sulfur compounds of DBT, BT, and TS, which was performed by Gao et al.38 All the results indicated that the extractive performance became better with the increment of the aromatic π-electron density. Therefore, as for different S-species (DBT, BT, and TS) in this paper, the desulfurization rates of the same CMPSsupported IL followed the order of DBT > BT > TS. Third, the ionic liquid extractants M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) were employed in real oil. The desulfurization rate of those ILs in real oil was 72.41%, 53.16%, and 50.28%, respectively. They were lower than that from model oil. The reason might be that the real oil had more complex S-species than model gasoline, such as thiols, and here it should be noted that the extraction technique of thiols was different from those of thiophene and its derivatives, which has been elucidated in the Introduction section. 3.5. Desulfurization Rates of M/CMPS-Im(Cl) ILs for Different Initial Sulfur Concentrations. The desulfurization rates of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) for different initial sulfur concentrations are displayed in Figure 4. As indicated in Figure 4, the desulfurization rates increased with the increment of initial sulfur concentration. 3.6. Effect of Mass Ratio of Model Gasoline to M/ CMPS-Im(Cl) ILs on Desulfurization Rates. The effect of mass ratio of model gasoline to extractant on the extraction properties of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) is shown in Figure 5. The mass ratio of model gasoline to extractant had a strong influence on desulfurization rates. The desulfurization rate decreased with the increment of mass ratio of model gasoline to extractant. For a certain mass ratio of model gasoline to extractant, CuCl/CMPS-Im(Cl) exhibited the best activity. 3.7. Effect of Extraction Time on Desulfurization Rates of M/CMPS-Im (Cl) ILs. The effect of extraction time on desulfurization rates of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) is shown in Figure 6. It could be observed that the desulfurization rates increased with the increment of extraction time, obviously. The extraction equilibrium was reached after 5 h. In order to make a complete extraction process, we chose 8 h as the extraction time.

Figure 3. Whole (a) and magnified (b) SEM images of CMPS particles and whole (c) and magnified (d) SEM images of CuCl/ CMPS-Im(Cl) particles.

CMPS-Im(Cl) particles with spherical structure have been fabricated by grafted methods, and the diameters of the spherical particles were all in the range of 250−300 μm, as shown in parts a and c of Figure 3, respectively. It indicated that the particle sizes had no obvious differences when metal chlorides imidazolium IL was supported onto the surface of CMPS. Otherwise, it could be observed that the surface of CuCl/CMPS-Im(Cl) particles shown in Figure 3d was much plainer than that of the CMPS particle in Figure 3b. The reason for this was that a compact and thin layer of imidazolium ILs have covered the original rough surface of CMPS spherical particles. 3.4. Investigation on Desulfurization Rates of M/ CMPS-Im(Cl) ILs. The effects of CMPS, CMPS-Im(Cl), and M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) samples on the removal of different sulfur compounds, such as TS, BT, and DBT, were investigated, as shown in Table 1. First, it should be pointed out that the desulfurization rates (thiophene) of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3), as shown in Table 1, were much higher than those of CMPS (14.31%) and CMPS-Im(Cl) (27.22%). The reason for this was that metal chlorides supported on the CMPS-Im(Cl) strongly improved the desulfurization rates, which were ascribed to the metal ions Cu+, Zn2+, and Fe3+, and could form π-complexes with aromatics.36,37 The order of extraction capacity of M/CMPS-Im(Cl) was CuCl/CMPS-Im(Cl) > ZnCl2/CMPS-Im(Cl) > FeCl3/CMPS-Im(Cl). The reason was that the π-complexation capability of Cu+ with thiophene was stronger than those of Fe3+ and Zn2+.36 Second, from Table 1, it could be concluded that the desulfurization rates using 3421



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two techniques for the regeneration of extractants, the thermal treating and the solvent elution.39 In this work, the regeneration of extractants under investigation was carried out by the thermal treatment, so they were heated in vacuum (−0.085 MPa) at 80 °C for 4 h to remove the feed adsorbed on the resin surface; the results are displayed in Figure 7. As indicated in Figure 7, there were no great differences in desulfurization rates

Figure 4. Desulfurization rates of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILs for different initial sulfur concentrations. Extraction time 8 h; extraction temperature 30 °C.

Figure 7. Regeneration of M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILs. Regeneration conditions: heated in vacuum (−0.085 MPa) at 80 °C for 4 h.

and extractive capacity between fresh and regenerated M/ CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) ILs. The desulfurization rates of the first round for CuCl/CMPS-Im(Cl), ZnCl2/CMPS-Im(Cl), and FeCl3/CMPS-Im(Cl) ILs were 68.62%, 55.01%, and 51.26%, respectively. The desulfurization rates of the first regenerated CuCl/CMPS-Im(Cl), ZnCl2/ CMPS-Im(Cl), and FeCl3/CMPS-Im(Cl) ILs were 65.00%, 51.80%, and 49.50%, respectively. Until the sixth round, the desulfurization rates of CuCl/CMPS-Im(Cl), ZnCl2/CMPSIm(Cl), and FeCl3/CMPS-Im(Cl) ILs decreased up to 60.08%, 44.32%, and 42.11%, respectively. The extraction ability of regenerated CuCl/CMPS-Im(Cl), ZnCl2/CMPS-Im(Cl), and FeCl3/CMPS-Im(Cl) ILs until the sixth round still maintains 87.55%, 80.57%, and 82.15% of the fresh extractants, respectively. It indicated that extractants synthesized in this work possessed an excellent recycling property.

Figure 5. Effect of model gasoline to extractant mass ratio on desulfurization rates. Extraction time 8 h; extraction temperature 30 °C.

4. CONCLUSIONS The main focus of the present work was concerned with discovering the efficient synthesis method of CMPS-supported metal chlorides IL extractants, along with their desulfurization rates and regeneration. On the basis of grafted methods, CMPS-supported imidazolium-based ILs M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) with spherical structure have been fabricated, and their structures have been characterized by FTIR, XPS, and SEM techniques. The results confirmed that CMPS and CuCl/ CMPS-Im(Cl) particles possessed the spherical structures, and the diameters of the spherical particles were all in the range of 250−300 μm. Furthermore, the original rough surface of CMPS was covered with a thin and compact layer of extraction activity components. On the other hand, the synthesized CMPS-supported imidazolium-based ILs have been employed to extract thiophene and its derivatives from model gasoline (n-

Figure 6. Effect of extraction time on desulfurization rates. Mass ratio of model gasoline to extractant 5:1; extraction temperature 30 °C.

3.8. Regeneration of M/CMPS-Im(Cl) ILs. The regeneration and subsequent recycling of extractants are important for the industrial application of an extraction. Generally, there are 3422



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(12) Bösmann, A.; Datsevich, L.; Jess, A.; Lauter, A.; Schmitz, C.; Wasserscheid, P. Deep Desulfurization of Diesel Fuel by Extraction with Ionic Liquids. Chem. Commun. 2001, 23, 2494. (13) Kêdra-Królik, K.; Mutelet, F.; Jaubert, J.-N. Extraction of Thiophene or Pyridine from N-Heptane Using Ionic Liquids. Gasoline and Diesel Desulfurization. Ind. Eng. Chem. Res. 2011, 50, 2296. (14) Mochizuki, Y.; Sugawara, K. Removal of Organic Sulfur from Hydrocarbon Resources Using Ionic Liquids. Energy Fuels 2008, 22, 3303. (15) Kulkarni, P. S.; Afonso, C. A. M. Deep Desulfurization of Diesel Fuel Using Ionic Liquids: Current Status and Future Challenges. Green Chem. 2010, 12, 1139. (16) Wang, X. M.; Han, M. J.; Wan, H.; Yang, C.; Guan, G. F. Study on Extraction of Thiophene from Model Gasoline with Brønsted Acidic Ionic Liquids. Front. Chem. Sci. Eng. 2011, 5 (1), 107. (17) Hansmeier, A. R.; Meindersma, G. W.; de Haan, A. B. Desulfurization and Denitrogenation of Gasoline and Diesel Fuels by Means of Ionic Liquids. Green Chem. 2011, 13, 1907. (18) Nefedieva, M.; Lebedeva, O.; Kultin, D.; Kustov, L.; Borisenkova, S.; Krasovskiy, V. Ionic Liquids Based on Imidazolium Tetrafluoroborate for the Removal of Aromatic Sulfur-Containing Compounds from Hydrocarbon Mixtures. Green Chem. 2010, 12, 346. (19) Francisco, M.; Arce, A.; Soto, A. Ionic Liquids on Desulfurization of Fuel Oils. Fluid Phase Equilib. 2010, 294, 39. (20) Zhang, S.; Zhang, Q.; Zhang, Z. C. Extractive Desulfurization and Denitrogenation of Fuels Using Ionic Liquids. Ind. Eng. Chem. Res. 2004, 43, 614. (21) Ko, N. K.; Lee, J. S.; Huh, E. S.; Lee, H.; Jung, K. D.; Kim, H. S.; Cheong, M. Extractive Desulfurization Using Fe-Containing Ionic Liquids. Energy Fuels 2008, 22, 1687. (22) Huang, C.; Chen, B.; Zhang, J.; Liu, Z.; Li, Y. Desulfurization of Gasoline by Extraction with New Ionic Liquids. Energy Fuels 2004, 18, 1862. (23) Alonso, L.; Arce, A.; Francisco, M.; Soto, A. Extraction Ability of Nitrogen-Containing Compounds Involved in the Desulfurization of Fuels by Using Ionic Liquids. J. Chem. Eng. Data 2010, 55, 3262. (24) Kim, D. W.; Hong, D. J.; Jang, K. S.; Chia, D. Y. Structural Modification of Polymer-Supported Ionic Liquids as Catalysts for Nucleophilic Substitution Reactions Including Fluorination. Adv. Synth. Catal. 2006, 348, 1719. (25) Xu, Zh. J.; Wan, H.; Miao, J. M.; Han, M. J.; Yang, C.; Guan, G. F. Reusable and Efficient Polystyrene-Supported Acidic Ionic Liquid Catalyst for Esterifications. J. Mol. Catal. A: Chem. 2010, 332, 152. (26) Burguete, M. I.; Erythropel, H.; Garcia-Verdugo, E.; Luis, S. V.; Sans, V. Base Supported Ionic Liquid-Like Phases as Catalysts for the Batch and Continuous-Flow Henry Reaction. Green Chem. 2008, 10, 401. (27) Bao, Q. X.; Qiao, K.; Tomida, D.; Yokoyama, C. Acetalization of Carbonyl Compounds Catalyzed by GaCl 3 Immobilized on Imidazolium−Styrene Copolymers. Catal. Commun. 2009, 10, 1625. (28) Xie, L. L.; Favre-Reguillon, A.; Wang, X. X.; Fu, X. Z.; Vrinat, M.; Lemaire, M. Selective Extraction of Neutral Nitrogen-Containing Compounds from Straight-Run Diesel Feed Using Polymer-Supported Ionic Liquid Moieties. Ind. Eng. Chem. Res. 2009, 48, 3973. (29) Liu, Q. Q.; Wang, L.; Xiao, A. G.; Yu, H. J.; Tan, Q. H. A HyperCross-Linked Polystyrene with Nano-Pore Structure. Eur. Polym. J. 2008, 44, 2516. (30) Fontanalsa, N.; Ronkab, S.; Borrulla, F.; Trochimczukb, A. W.; Marcé, R. M. Supported Imidazolium Ionic Liquid Phases: A New Material for Solid-Phase Extraction. Talanta 2009, 80, 250. (31) Rosalynn, Q.; Ellen, S. G. Polystyrene Formation on MonolayerModified Nitinol Effectively Controls Corrosion. Langmuir 2008, 24, 10858. (32) Wu, Q.; Chen, H.; Han, M. H.; Wang, D. Z.; Wang, J. F. Transesterification of Cottonseed Oil Catalyzed by Brønsted Acidic Ionic Liquids. Ind. Eng. Chem. Res. 2007, 46, 7955. (33) Qiao, K.; Hagiwara, H.; Yokoyama, C. Acidic Ionic LiquidModified Silica Gel as Novel Solid Catalysts for Esterification and Nitration Reactions. J. Mol. Catal. A: Chem. 2006, 246, 65.

octane/thiophene) under certain conditions. The results showed that M/CMPS-Im(Cl) (M = CuCl, ZnCl2, and FeCl3) extractants were efficient to extract the thiophene and its derivatives from model gasoline at room temperature. For a given CMPS-supported imidazolium-based IL, the order of extraction capacity of extractants was CuCl/CMPS-Im(Cl) > ZnCl2/CMPS-Im(Cl) > FeCl3/CMPS-Im(Cl), which was ascribed to the stronger π-complexation capability of Cu+ with thiophene than those of Fe3+ and Zn2+. Meanwhile, the sulfur removal selectivity of sulfur compounds followed the order of TS < BT < DBT under the same conditions; it indicated that the extraction was favored for those aromatic heterocyclic sulfur compounds with higher density aromatic πelectrons density. Finally, regeneration and subsequent recycling of M/CMPS-Im(Cl) ILs have been investigated. The results showed that M/CMPS-Im(Cl) ILs could be used as promising extractants for the extractive desulfurization of future industrial application due to their higher desulfurization rates and easy separation from the gasoline.

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Corresponding Author

*Tel.: +86-25-83587198. Fax: +86-25-83587198. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the National Nature Science Foundation of China (no. 21176121, 21003074) and the Natural Science Fund for Colleges and Universities in Jiangsu province (09KJB530002).

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REFERENCES

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