Phosphotungstic Acid Immobilized on Ionic Liquid-Modified SBA-15

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Phosphotungstic Acid Immobilized on Ionic Liquid-modified SBA-15: Efficient Hydrophobic Heterogeneous Catalyst for Oxidative Desulfurization in Fuel Jun Xiong, Wenshuai Zhu, Wenjing Ding, Lei Yang, Yanhong Chao, Hongping Li, Fengxia Zhu, and Huaming Li Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie503322a • Publication Date (Web): 26 Nov 2014 Downloaded from http://pubs.acs.org on December 3, 2014

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Industrial & Engineering Chemistry Research

Phosphotungstic Acid Immobilized on Ionic Liquid-modified SBA-15: Efficient Hydrophobic Heterogeneous Catalyst for Oxidative Desulfurization in Fuel Jun Xiong a, Wenshuai Zhua,*, Wenjing Ding a, Lei Yang a, Yanhong Chao a, Hongping Li a, Fengxia Zhu b, and Huaming Lia,* a

School of Chemistry and Chemical Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang

212013 (PR China), b

School of Chemistry and Chemical Engineering, Huaiyin Normal University,

E-mail: [email protected] (H.M. Li), [email protected] (W.S. Zhu)

Abstract: A heterogeneous catalyst system was synthesized by immobilizing phosphotungstic acid on ionic liquid-modified mesoporous silica SBA-15 and applied in oxidative desulfurization. Structure and properties of catalyst were characterized by XRD, FT-IR, XPS, N2 adsorption-desorption, SEM, TEM and the contact angle. The results demonstrated that the synthesized catalyst possessed the ordered mesopore structure and high special surface area. Due to the introduction of imidazole-based ionic liquid, the catalyst exhibited good wettability for model oil, which had significantly contribution to desulfurization activity. Both DBT and 4,6-DMDBT could be removed completely at mild conditions (60 oC, 40 min). The removal of BT also can reach 81.3% within 60 min. Furthermore, the catalyst was recovered and reused in four reaction runs with a slight decrease in activity. Keywords: heterogeneous catalyst; hydrophobic; ionic liquid; mesoporous silica; oxidative desulfurization 1. Introduction With the increasingly stringent regulations and fuel specifications of petroleum refining industry in

ACS Paragon Plus Environment


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worldwide, the deep removal of sulfur compounds from fuels had attracted more and more attentions.1,

2

However, the conventional catalytic hydrodesulfurization (HDS) required high

temperature and high hydrogen pressure. It also exhibited less effective for refractory aromatic thiophenes such as benzothiophene (BT) and dibenzothiophene (DBT).3, 4 Hence, lots of different approaches have been explored, including adsorptive desulfurization (ADS),5-8 oxidative desulfurization (ODS),9-17 and extractive desulfurization18-20. Among them, ODS has received massive research interests, because it not only can carried out under mild conditions but also exhibits high efficient removal of aromatic sulfur compounds. Up to now, different catalytic systems have been used in ODS, such as organic acid,21,

22

polyoxometalate,23-27 ionic liquids,28-30 Fenton reagent31-33 and so on. They all were regarded to be effective strategies for removal of sulfur compounds. Especially, polyoxometalate due to the unique properties, including fast reversible multielectron redox transformation under mild conditions, thermal and hydrolytic stability, have received increasing attention as catalysts for oxidative desulfurization.34, 35 For example, Yazu et al.36 used the 12-tungstophosphoric acid as the catalyst in n-octane/acetonitrile biphasic system for catalytic oxidation the DBT. The removal sulfur could reach 96.36%. Wang et al.37 reported several Keggin-type POMs for catalytic oxidation DBT with H2O2 as oxidant, acetonitrile as extractant. H3PW6Mo6O40 was found to have the high desulfurization efficiency (99.79%). Te et al.38 studied a series of polyoxometalate/H2O2 systems to evaluate for dibenzothiophene oxidation. And the sulfur removal could reach 100%. It can be seen that these homogeneous catalysts are normally exhibited high activity and selectivity. However, their separation and recovery can be difficult, which could not conducive to the industrial application. Therefore, different methodologies have been used to immobilize the homogeneous


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catalysts on various supports as the heterogeneous catalysts. Recent decade, the oxidative desulfurization with polyoxometalate-based heterogeneous catalysts have been studied.34,

39-43

However, though the heterogeneous catalysts showed excellent performance in catalyst recovery and reuse, the catalytic sites were lower exposure to the reactants. Thus, their activities were usually lower than those of homogeneous catalysts. What’s worse, heterogeneous catalyst also required relative long reaction time and easily leached of active species into the reaction medium. Therefore, the catalysts with high activity and good recycle are still needs to be fully exploited. Recently, ordered mesoporous sillicas, such as SBA-15, have attracted increasing interest due to their large specific surface area, uniform internal pore structure, controlled pore size, pore volume, and higher hydrothermal stability.44, 45 Because of these characteristics, SBA-15 has been regarded as suitable support of catalysts to form heterogeneous catalysts.46 However, there still exist some problems of the SBA-15 supported catalysts. The active species are easily leaching into the reaction medium as the weakly interaction between the active species and SBA-15. On the other hand, due to the hydrophilic nature of SBA-15, for reactions containing both aqueous phase and hydrophobic starting materials, the activity of these catalysts could be significantly influenced.47 It has been reported that the hydrophobization of mesoporous support could markedly enhance the stability and performance of the catalyst system.47,48 Considering these facts, we attempted to design a catalyst system dissolving active species H3PW12O40 (HPW) in ionic liquid (IL) functionalized on SBA-15 and employ it for oxidative desulfurization. The HPW could be steadily immobilized in the SBA-15 across by IL. After the HPW-IL was immobilized in SBA-15, the wettability of HPW-IL/SBA-15 material could be changed from hydrophilic to hydrophobic. Therefore, the hydrophobic HPW-IL/SBA-15 material could have good wettability for the model oil and provide higher



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exposure active sites to the reactants. This strategy combined the advantages of heteropoly acid and SBA-15, and solved the shortage of heterogeneous catalysts. The results demonstrated the catalyst system with high surface area, high accessibility of substrate and oxidant, and no leaching of active species in the reaction media. This synthesis procedure can be extended to a general strategy for immobilizing functionalized IL on mesoporous materials to construct hydrophobic structure and thus make the heterogeneous catalysts with high activity.

2. Experimental 2.1. Materials. All the reagents were analytical purity and were used as received. Benzothiophene (BT), Dibenzothiophene

(DBT),

4,6-dimethyldibenzothiophene

(4,6-DMDBT)

and

poly(ethyleneglycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic P123) were purchased from Sigma-Aldrich. Commercially available 30 wt % H2O2, phosphotungstic acid hydrate (H3PW12O40), n-octane, tetradecane, ethylsilicate (TEOS) and N-methylimidazole were purchased from Sinopharm Chemical Reagent. (3-chloropropyl)Trimethoxysilan (98%) were marketed by Aladdin Chemistry.

2.2. Catalysts preparation SBA-15 was synthesized according to the procedures reported previously.49 P123 was dissolved in 1.6 M HCl solution with stirring and then the silica source TEOS was added P123 solution with stirring for 24 h at 40 oC. The mixture was hydrothermally treated for 24 h at 100 oC. The precipitates were filtered, washed with distilled water, dried overnight in an oven at room


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temperature, and then calcined in air at 550 oC for 5 h. 1. Synthesis of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium chloride ([pmim]Cl) The mixture of N-methylimidazole (freshly distilled) (10.3160 g, 0.1258 mol) and (3-chloropropyl)Trimethoxysilan (25 g, 0.1258 mol) was refluxed at 95 oC for 24 h. After cooling to room temperature, the reaction mixture was washed with diethyl ether and dried under vacuum. The dried temperature was 40 oC. 2. Grafting of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium chloride ([pmim]Cl) on SBA-15 ([pmim]Cl-SBA-15, denoted as IL/SBA-15) SBA-15 (1 g) was dispersed in 50 mL dried toluene and treated with 0.5 g [pmim]Cl. The mixture was heated under reflux (90 oC) for 16 h. After cooling to room temperature, the solid was isolated by filtration and dried under high vacuum (60 oC). Then, the unreacted [pmim]Cl was removed by 48 h extraction with boiling dichloromethane. White powder of IL/SBA-15 was achieved under vacuum. The dried temperature was 50 oC. 3. Preparation of immobilized HPW-based ionic liquid (HPW-IL/SBA-15) Catalysts of xHPW-IL/SBA-15 with different loadings of H3PW12O40 on IL/SBA-15 were prepared by stirring the suspension of 0.5 g IL/SBA-15 in 50 ml of deionized water containing various amount of HPW (0.05, 0.1, or 0.25 g, respectively), where x represented weight of HPW in the samples. Then, the solid was isolated by filtration and washed with deionized water. The resulting solid was dried in vacuum (50 oC) to produce HPW-IL/SBA-15. (Scheme 1) 4. Preparation of HPW/SBA-15 Sample HPW/SBA-15 was prepared by stirring the suspension of 0.5 g SBA-15 in 50 ml of deionized water containing 0.1 g HPW. Then, the solid was isolated by filtration and washed with



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deionized water. The resulting solid was dried in vacuum (50 oC) to produce HPW/SBA-15.

2.3. Catalyst characterization Powder X-ray diffraction (XRD) analysis was performed on Bruker D8 diffractometer with high-intensity Cu Ka (λ = 1.54 Å). Transmission electron microscopy (TEM) micrographs were recorded on a JEOL-JEM-2010 (JEOL, Japan) operating at 200 kV. N2 adsorption–desorption isotherms and porosity properties were investigated using a TriStar II 3020 surface area and porosity analyzer (Micromeritics Instrument) at 77 K. X-ray photoemission spectroscopy (XPS) was tested on a VG MultiLab 2000 system with a monochromatic Mg-Ka source operated at 20 kV. The field-emission scanning electron microscopy (SEM) measurements were carried out with a field-emission

scanning

electron

microscope

(JEOL JSM-7001F)

equipped

with

an

energy-dispersive X-ray spectroscope (EDS) operated at an acceleration voltage of 10 kV.

2.4. Oxidative desulfurization of model oil. Model oil was prepared by dissolving DBT, BT, and 4,6-DMDBT, in n-octane, with a corresponding S-content of 500, 250, and 185 ppm, respectively. Desulfurization was carried out in a 40 mL two-necked flask. 0.01 g catalyst and 5 ml model oil were added to the flask in turn. Then 30 wt % hydrogen peroxide was added into the mixture with continuous magnetic stirring at corresponding temperature. The sulfur-containing compounds concentrations in model oil after the reaction were analyzed by Gas Chromatography-Flame Ionization Detector (GC-FID) with tetradecane as the internal standard (Agilent 7890A; HP-5, 30 m × 0.32 mm i.d. × 0.25 µm; FID: Agilent). The conversion of


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DBT in the model oil was used to calculate the removal of sulfur compounds. The oxidized S-compound was characterized by Gas Chromatography-Mass Spectrometer (GC-MS) (Agilent 7890/5975C-Gas Chromatography (GC)/Mass Selective Detector (MSD); HP-5 MS column, 30 m × 250 µm i.d. × 0.25 µm; temperature program: 100 oC temperature rising 15 o

C/min-200 oC for 10 min).

3. Results and discussion 3.1. XRD Analysis The

X-ray diffraction

(XRD)

patterns

of

the

SBA-15

and

the

functionalized

0.1HPW-IL/SBA-15 catalysts are presented in ure 1. Both the SBA-15 and HPW-IL/SBA-15 samples (ure 1a) displayed the (100) characteristic peak of SBA-15 at around 1.0° (2θ). At the same time, two weak peaks in the range of 2θ = 1-3o were found, which ascribed to the (110), (200) peaks of SBA-15. This result indicated that after the HPW-IL was introduced, the synthetic material could remain the well-ordered hexagonal mesostructure of SBA-15. It was noted that the intensities of these characteristic peaks of HPW-IL/SBA-15 are lower than those of SBA-15. This may due to the introduction of HPW-IL, the interaction would form between the organic group of the HPW-IL and silicon wall. Thus, it will affect the mesoporous channels. The HPW-IL inside the mesoporoous channels of SBA-15 leaded to the degree of order with a little decrease. However, the mesoporous structure of support was well retained. The similar result can also be found in other reports.50-52 The wide-angle XRD pattern of the HPW and 0.1HPW-IL/SBA-15 sample is presented in Figure 1b. No remarkable peaks of HPW were found on wide-angle XRD pattern of 0.1HPW-IL/SBA-15 sample, which implied that the HPW may be due to a well dispersion and low content of HPW supported on



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SBA-15.

3.2. XPS and FT-IR analysis The surface composition and chemical states of the HPW-IL/SBA-15 sample are investigated by X-ray photoelectron spectroscopy (XPS) analysis. The survey XPS spectrum showed that the HPW-IL/SBA-15 sample was composed of the elements of Si, O, C, N, P and W. (Figure 2a). Figure 2b shows the high resolution Si2p XPS spectrum of the sample. The O1s peak was associated with the binding energy of 533.2 eV (Figure 2c). The Si2p and O1s peaks indicated the existence of SiO2 in the sample. The Figure 2d, 2e show the C1s and N1s peaks respectively, which attributed to the imidazole part of ionic liquid in the sample. The high resolution XPS spectra of P2p and W4f in the HPW-IL/SBA-15 sample are shown in Figure 2f, 2g, which indicated that the HPW was introduced to the as-prepared sample. The FT-IR analysis was also provided to further determine the structure of HPW-IL/SBA-15 sample (Figure S1). With regard to the SBA-15, the absorption peak at 1086 cm-1 could be attributed to the stretching mode of Si-O-Si. The characteristic peak at 954 cm-1 was ascribed to the Si-OH vibration peak. For the HPW-IL/SBA-15 sample, it was noted that a little shift of 954 cm-1 characteristic peak appeared, indicating the interaction between HPW-IL and SBA-15. The result of XPS and FT-IR analysis confirmed that phosphotungstic acid was successfully immobilized on ionic liquid-modified SBA-15 and still remained the structure of SBA-15.

3.3. Nitrogen adsorption-desorption analysis The N2 adsorption-desorption isotherms and pore size distributions of SBA-15, IL/SBA-15, and HPW-IL/SBA-15 are presented in Figure 3. As it can be seen from Figure 3 that all the


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adsorption-desorption isotherms displayed typical IV-type curves with an H1-type hysteresis loop, characteristic of the mesoporous samples with uniform cylindrical pores. This implied that the order mesostructure was well remained after supporting HPW-IL on SBA-15. With the introduction of IL and HPW/IL, the height of the capillary condensation decreased step by step, illustrating that HPW/IL was successfully supported on SBA-15. This phenomenon was coincident with the low-angel XRD. At the same time, it can be observed that these three samples exhibited a sharp increase in adsorption at the relative pressure (P/P0) range of 0.6-0.8, implying the modified samples with large mesopores and narrow pore size distributions, similar with the SBA-15. The pore size distribution, which was obtained using the Barrett-Joyner-Halenda model, revealed a sharp peek centered at 6.3 nm (Figure 3, inset). The BET surface area of SBA-15, IL/SBA-15, and HPW-IL/SBA-15 samples were 841.67, 665.78 and 535.83 m2 g-1, respectively. The decreased BET surface area was ascribed to the IL and HPW/IL had been successfully grafted into the SBA-15.

3.4. SEM, TEM and EDS analysis The surface morphology of the SBA-15 and HPW-IL/SBA-15 were examined by SEM analysis. It can be seen from Figure S2 that the SBA-15 was a rod-like structure which aggregate together. For the HPW-IL/SBA-15, similar structure can be found. TEM analysis was used to further determine the structural information of the as-prepared sample. It can be seen from Figure 4A, 4B that the TEM image shows the high ordered hexagonal mesostructure in the SBA-15 sample. When the HPW-IL was loaded (Figure 4C), the HPW was distributed in the pore wall uniformly. As shown in Figure 4C, it can be seen that the hexagonal mesostructure of SBA-15 was still maintained after the introduction of HPW-IL. This was consists



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with the above results that HPW has been successfully introduced into the pores of the inner wall of the material which constructing the uniform active centre. The EDS pattern (Figure 4D) indicated the HPW-IL/SBA-15 sample contained C, N, O, P, W, and Si element. It proved that the sample prepared was HPW-IL/SBA-15 material.

3.5. Influence of different catalyst on removal of DBT Figure 5 depicts the removal efficiency of DBT over different catalysts. It can be seen, the catalyst without IL, HPW-SBA-15, exhibited poor desulfurization efficiency and the sulfur removal was only 13.6%. Notably, the removal efficiency of HPW-IL/SBA-15 can reach 100% after oxidization for 40 min. This significant improvement indicated that the introduction of IL played important role in the desulfurization efficiency of catalysts. The contact angle (CA) of HPW-SBA-15 and HPW-IL/SBA-15 sample was measured to account for the significant improvement of desulfurization rate. When the water droplet was brought in contact with the surface of catalyst, the CA of HPW-IL/SBA-15 sample was measured to be 55o (Figure 6A). However, the CA was zero for a water droplet in contact with the surface of HPW-SBA-15 (Figure 6B). It revealed that the HPW-IL/SBA-15 was relatively hydrophobic in comparison with HPW-SBA-15. It was interesting to note that the ILs functionalized on the SBA-15 support enhanced hydrophobicity of catalyst. As it was known, the hydrophobic materials could have a good miscibility in model oil. In this system, the HPW-IL functionalized SBA-15 was hydrophobic and could provide higher degree of exposure of the catalytic sites in model oil. Therefore, the enhanced removal of DBT was strongly related to the unique features of good miscibility of the hydrophobic HPW-IL/SBA-15 for the reactants.


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To study the effect of the loading amount of HPW on the sulfur removal, the oxidation of DBT in the model oil was carried out with various loading amount at 0.05, 0.1 and 0.25 g, respectively. From Figure 7, it could be seen that the loading amount of HPW played an important role in the desulfurization efficiency. The removal of DBT enhanced when loading amount of HPW increased from 0.05 to 0.1 g, and decreased when the loading amount was 0.25 g. The 0.1HPW-IL/SBA-15 showed the highest activity. The decreased sulfur removal was attributed to that the over much loading amount of HPW blocking the pore channel of SBA-15, and hence the sulfur removal was decreased.

3.6. Effect of different reaction temperature on DBT removal and activation energy for oxidation DBT. To investigate the effect of temperature on the desulfurization system, the experiments on sulfur removal of DBT versus reaction time at different temperatures were done, and the results are shown in Figure 8. As it can be seen, the sulfur removal was poor at the low temperatures. The sulfur removal was only 2.6% and 12.9% at 30 °C and 40 °C, respectively. When the temperature increased at 50 °C, the sulfur removal enhanced greatly and the 60 °C had the highest sulfur removal of DBT. This phenomenon might occur because the supported imidazole based ionic liquid almost presented solid state at low temperature. With the temperature increasing, the ionic liquid changed from solid to liquid state. The liquid state was beneficial for mass transfer. Therefore, in this system, the enhanced temperature benefited for the desulfurization process. The process of oxidation of DBT with 0.1HPW-IL/SBA-15 as the catalyst was investigated and fitted to the pseudo-first-order kinetic model (Figure S3). The first-order rate equation



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was ln(Ct / C0 ) = − kt , where C0 and Ct (mg L-1) is the concentration of sulfur at initial and t (min), k is the rate constant. The rate constants were 0.0726 and 0.143 min-1 at 323K and 333K, respectively. The Arrhenius equation is k = A exp( − as ln k = ln A −

Ea ) . It also can be expressed RT

Ea . A plot of lnk versus 1/T allows us to calculate the active energy Ea (slope = RT

-Ea/R). Based on these data, 56.6 kJ mol-1 active energy was obtained, which was in good agreement with other reports about polyoxometalate/H2O2 systems.54,55

3.7. Influence of the amount of H2O2 on the sulfur removal In order to study effect of H2O2 amount on the catalytic activity of 0.1HPW-IL/SBA-15, the different H2O2/DBT (O/S) molar ratios were used to oxidation of DBT at 60 °C (Figure 9). When the O/S molar ratios increased from 2 to 4, DBT removal enhanced. The sulfur removal can only reach 73.0% of O/S = 2:1 (0.53 mmol H2O2) within 60 min. And the sulfur removal could reach 100 % of O/S = 3:1 (0.8 mmol H2O2) at 40 min. The O/S = 4:1 (1.07 mmol H2O2) exhibited the fastest sulfur removal, which could have 100 % sulfur removal with only 20 min. In this catalysis system, the higher O/S molar ratios promoted the desulfuration process. Taking into account economic aspects, the optimized H2O2/DBT molar ratio was selected as 3:1 (0.8 mmol H2O2).

3.8. Sulfur removal of different sulfur-containing compounds It was known that there were many different sulfur-containing compounds in real fuel. Thus, other inflexible sulfur-containing compounds, such as BT and 4,6-DMDBT, were chosen to further investigate the catalytic activity of HPW-IL/SBA-15. As it can be seen in Figure 10, sulfur removal of 4,6-DMDBT and DBT can reach 100% after 30 min and 40 min, respectively. And the BT can


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reach 81.3% after 60 min. It can be concluded that besides DBT, BT and 4,6-DMDBT also exhibited excellent sulfur removal. The difference in sulfur removal could be attributed to the different electron density of the sulfur atom of these sulfur-containing compounds.53 The electron density on the sulfur atom decreases in following order: 4,6-DMDBT (5.760) > DBT (5.758)> BT (5.739).21 Therefore, the sulfur removal decreased in the order of 4,6-DMDBT > DBT> BT with 0.1HPW-IL/SBA-15 as the catalyst.

3.9. The mechanism of catalytic oxidation process To study the mechanism of catalytic oxidation desulfurization, DBT in model oil at different reaction times were measured by GC-MS. When the reaction time was 20 min, two main compounds were detected. The species A and B in oil phase ascribed to the DBT and DBTO2, respectively (Figure 11). At the reaction time of 40 min, only one compound was detected which was assigned to DBTO2 (Figure 12). It indicated that the DBT can be oxidized to DBTO2 completely and thus reach the deep desulfurization. The excellent catalytic performance of HPW-IL/SBA-15 can be attributed to three aspects. On the one hand, the catalyst maintained the structure of SBA-15 with the high surface area and large mesopores, which were beneficial for mass transfer. On the other hand, the phosphotungstic acid could active hydrogen peroxide. The most important point was that due to the introduction of ionic liquid, the catalyst exhibited a somewhat hydrophobic property, which made the catalyst have good wettability for the model oil and provide higher exposure active sites to the reactants.

3.10. Effect of the Recycle of the Catalyst



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The recycling reactions (Figure 13) were carried out for the oxidation desulfurization of DBT by the 0.1HPW-IL/SBA-15 sample. After four cycles, the sulfur removal could still be maintained, and only 5.7% of efficiency was decreased. The results indicated that the HPW-IL/SBA-15 sample was stabile in this desulfurization system. To further confirm the stability of the HPW-IL/SBA-15 sample, the TEM of the 0.1HPW-IL/SBA-15 sample before and after the cycle reaction was contrasted (Figure 14). The results revealed that the ordered mesoporous structure of the 0.1HPW-IL/SBA-15 sample still existed after the cycle reactions. However, the TEM images of HPW-IL/SBA-15 sample after the cycle reactions showed that the image was blurred, which indicating some materials covered on the HPW-IL/SBA-15 sample. This result was attributed to the DBTO2 adsorbed on the surface of sample, and thus resulting in a little decreased desulfurization activity. After the cycle reactions, XPS of used catalyst was investigated. The survey XPS spectrum (Figure S4) shows that the main elements on the surface of used catalyst are C, N, O, P, W, Si and S, which demonstrated that IL and active HPW species presented in the spent catalyst and the DBTO2 was indeed adsorbed on the catalyst.

4. Conclusions In summary, HPW-IL immobilized in SBA-15 has been successfully synthesized through the one-pot procedure. The low-angle XRD, TEM and N2 adsorption-desorption indicated that HPW-IL/SBA-15 sample remained the mesoporous structure of SBA-15. The HPW-IL/SBA-15 catalysts displayed significant higher catalytic performance than HPW/SBA-15 for oxidative desulfurization of DBT. The 0.1HPW-IL/SBA-15 sample showed the optimal oxidative desulfurization efficiency, in which the sulfur removal of DBT could reach 100%. This enhanced


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catalytic performance of the HPW-IL/SBA-15 could be attributed to the good miscibility of the hydrophobic HPW-IL/SBA-15 for the reactants. Through the GC-MS analysis, DBTO2 was confirmed to be the only product of DBT oxidizing reaction. Our strategy may open an opportunity for wide applications in catalysis by immobilized functionalized IL to form hydrophobic materials.

Acknowledgements This work was financially supported by the National Nature Science Foundation of China (Nos. 21276117, 21376111, 21376109), Natural Science Foundation of Jiangsu Province (Nos. BK20131207), College Natural science research plan of Jiangsu province (13KJB150008), Doctoral Innovation Fund of Jiangsu Province (CXZZ13_0692).

Supporting Information Experimental details and additional data, FT-IR spectra and SEM images for materials characterization, pseudo-first-order oxidation of DBT, and XPS spectrum of the catalyst after cycles. This information is available free of charge via the Internet at http://pubs.acs.org/.

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(a) Intensity (a.u.)

(100)

(110)

(200)

SBA-15 IL/SBA-15 HPW-IL/SBA-15

1

2

3

4

2-Theta (degree)

(b) HPW HPW-IL/SBA-15

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10

20

30

40

50

60

70

80

2-Theta (degree)

Figure 1. (a) Low-angle and (b) wide-angle XRD patterns of samples



O1s

(b)

1000

800

600

400

Intensity (a.u.)

Si2p

O2s W4f

Si2s P2p Si2p

W4p1 W4p3 N1s

C1s W4d3 W4d5

O KLL

Intensity (a.u.)

(a) Survey

200

0

110

108

106

(d)

O1s

102

100

98

C1s

Intensity (a.u.)

Intensity (a.u.)

(c)

104

Binding Energy (eV)

Binding Energy (eV)

540

538

536

534

532

530

528

526

292

288

Binding Energy (eV)

284

280

Binding Energy (eV)

(e) N1s

P 2p

Intensity (a.u.)

(f)

Intensity (a.u.) 408

406

404

402

400

398

396

394

140

136

Binding Energy (ev)

132

128

124

120

Binding Energy (eV)

(g)

W4f

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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42

40

38

36

34

32

30

Binding Energy (eV)

Figure 2. XPS spectra of the 0.1 HPW-IL/SBA-15 sample. (a) Survey of the sample; (b) Si 2p; (c) O 1s; (d) C 1s; (e) N 1s; (f) P 2p; (g) W 4f.


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800 1.0

700 600 500 400

dV / dD (cm 3/g nm )

3 Quantity Absorbed (cm .g-1 STP)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.8 0.6 SBA-15 IL/SBA-15 HPW-IL/SBA-15

0.4 0.2 0.0 0

5

300

10 15 Pore Diameter (nm)

20

200

SBA-15 IL/SBA-15 HPW-IL/SBA-15

100 0 0.0

0.2

0.4

0.6

0.8

1.0

Relative Pressure (P/Po)

Figure 3. N2 adsorption-desorption isotherms and the BJH pore-size distribution curves (inset) of SBA-15, IL/SBA-15, and HPW-IL/SBA-15.



A

B

C

Si W

D

600

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

400

200

O

0

N C

W

50 nm

P 5

Energy (keV)

Figure 4. The TEM images of SBA-15 (A, B) and HPW-IL/SBA-15 (C); The EDS of HPW-IL-SBA-15 (D)


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100

Sulfur removal(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80 0.1HPW-IL/SBA-15 0.1HPW-SBA-15

60 40 20 0

10

20

30

40

50

60

Time/min

Figure 5. Oxidation removal of DBT on different catalysts HPW-IL/SBA-15 and HPW/SBA-15 Experimental Conditions: m (catalyst) = 0.01g, n(H2O2) = 0.8 mmol, T = 60oC



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6. Contact angle for a water droplet on the surface of HPW-IL/SBA-15 (A) and HPW/SBA-15 (B)


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100

Sulfur removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80 60 0.05HPW-IL/SBA-15 0.1HPW-IL/SBA-15 0.25HPW-IL/SBA-15

40 20 0 10

20

30

40

50

60

Time / min

Figure 7. Oxidation removal of DBT of different HPW loadings. Experimental Conditions: m (catalyst) = 0.01g, n (H2O2) = 0.8 mmol, T = 60oC



100 80

Sulfur removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

60 o

30 C o 40 C o 50 C o 60 C

40 20 0 10

20

30

40

50

60

Time / min

Figure 8. Effect of different reaction temperature on DBT removal Experimental Conditions: m (0.1HPW-IL/SBA-15) = 0.01g, n(H2O2) = 0.8 mmol


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80 60 40 20

70

60

val(%)

100

Sulfur Remo

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0

50

Tim

4:1 (O:S)

40

e/m

in

30

3:1 (O:S)

20

10

2:1 (O:S)

0

Figure 9. Effect of H2O2/DBT molar ratio on sulfur removal of DBT. Experimental Condition: m (0.1HPW-IL/SBA-15) = 0.01g, T = 60oC



100 80

Sulfur removal / %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

60 40 20

BT DBT 4,6-DMDBT

0 10

20

30

40

50

60

Time / min

Figure 10. The effect of sulfur-containing compounds on sulfur removal. Experimental Conditions: m (0.1HPW-IL/SBA-15) = 0.01g, n (H2O2) = 0.8 mmol, T = 60oC


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184.1

Abundance

A

4

6

8

10 t

12

14

16

S

139.1 69.0

92.0

50

100

150 m/z

200

250

216.0

B

Abundance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4

6

8

10 t

12

14

16

187.0 S

28.0

O

O

139.1

168.1

115.0 63.0 79.0

20

40

60

80 100 120 140 160 180 200 m/z

Figure 11. The mass spectrogram of oil phase after reaction 20 min



216.0 A

Abundance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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4

6

8

10 t

12

14

16

187.0 S O

139.1

O

168.1

115.1 63.0 39.1

50

87.0

100

150

200

250

m/z

Figure 12. The mass spectrogram of oil phase after reaction 40 min


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100

Sulfur removal (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80 60 40 20 0

1

2

3

4

Recycle Times

Figure 13. The recycle times on the removal of DBT with 0.1HPW-IL/SBA-15 as catalyst. Experimental Conditions: m (catalyst) = 0.01g, n (H2O2) = 0.8 mmol, T = 60oC, t = 1 h



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 14. The TEM images of HPW-IL/SBA-15 after reaction.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Scheme 1. Synthesis of HPW-IL/SBA-15 catalyst.


Phosphotungstic Acid Immobilized on Ionic Liquid-Modified SBA-15

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