Highly Efficient Benzothiophene Capture with a Metal-Modified Cu

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Highly Efficient Benzothiophene Capture with a Metal-Modified Cu-BTC Adsorbent Guihua Zhao, Qing Liu, Ning Tian, Le Yu, and Wei Dai Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01223 • Publication Date (Web): 17 May 2018 Downloaded from http://pubs.acs.org on May 17, 2018

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Energy & Fuels

Highly Efficient Benzothiophene Capture with a Metal-Modified Cu-BTC Adsorbent Guihua Zhao,† Qing Liu,† Ning Tian,† Le Yu,a Wei Dai*,† †Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, College of Chemistry and Life Science, Zhejiang Normal University, Jinhua 321004, People’s Republic of China

ABSTRACT: In order to construct more desirable adsorption affinity between the current MOFs and benzothiophene (BT), a novel desulfurizer (V/Cu-BTC, BTC represents 1,3,5-benzenetricarboxylic acid) was prepared by reducing Cu(II) to Cu(I) with V(III) on Cu-BTC using a hydrothermal synthesis method. Utilizing nitrogen adsorption-desorption,

powder

X-ray

diffraction

(XRD),

scanning

electron

microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), we approved that the modifications of those novel desulfurizers have been successfully realized and further compared their structural changes. The BT capture performance from the different simulated fuels with V/Cu-BTC was evaluated by batch tests. The results manifest that V/Cu-BTC exhibited impressive desulfurization capacity, which is grander to Cu-BTC and some other adsorbents reported previously. Additionally, due to sieving and inertia mechanisms, this adsorbent possessed an extremely high affinity for BT capture in presence of benzene. The V/Cu-BTC showed a remarkable stability in BT adsorption, maintaining more than 90 % initial sulfur uptake capacity after five regeneration times. In general, the V/Cu-BTC material exhibits a very beneficial for the adsorptive

ACS Paragon Plus Environment

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removal of BT. Key words: Benzothiophene; V/Cu-BTC; Adsorption, Sulfur capacity 1. INTRODUCTION Sulfur compounds are ubiquitous in fuels including gasoline, kerosene, diesel and so on. The massive burning of those fuels will inevitably lead to sulfide, which is not only deleterious to the catalysts in the hydrocarbon conversions but also detrimental to the environment and the welfare of human beings.1-5 Therefore, abating sulfur content in fuels is imperious. Adsorption is considered as a promising method for deep desulfurization attributable to some of its extraordinary advantages such as comparatively low cost, clement operation conditions, simplicity of design, and easy reproducibility, etc.6,7 Adsorption materials are the key and core in industrial fields where desulfurization is crucial. Nowadays, thanks to these innovative inventions of various adsorbents including inorganic (e.g. activated carbon, zeolites and active alumina)8-10 and organic porous materials (e.g. porous resin),11 rapid development in adsorptive desulfurization technology has been developed. However, designing of the shape and regulating the pore sizes of the mentioned above types of adsorbents remain tough tasks, and those difficulties genuinely hindered the effective adsorption removal of organosulfur species such as BT.12,13 Recently, an organic-inorganic material, MOFs (Metal Organic Frameworks) combing metal components and organic ligand, has achieved significantly progress in the field of deep desulfurization due to the high porosity, open metal sites, and feasibility of changing their pore scale from micropores to mesopores through the


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adjustment of the connectivity between the metal part and the organic section.14,15 For example, one of the most representative MOFs material, Cu-BTC (HKUST-1) has been reported that it shows excellent adsorption performance towards organosulfur compounds.16 Tenable theories have been adopted in explaining the mechanism of the impressive adsorptive ability of MOFs for sulfur compounds capture. Based on the Pearson’s hard and soft acid−base theory, as soft bases, the thiophenic sulfur compounds are firmly appealed to the metal ions such as Zn(II), Ni(II), Cu(II), Cu(I), and Ag(I) (serving as soft Lewis acid).17,18 Besides, π-complexation, as an another commonly accepted mechanism for adsorption desulfurization is reported by Prof. Ralph T. Yang.19 The mechanism emphasizes that close interaction between cations of d-block metals and the thiophenic sulfur molecules, which is realized through π-complexation contributes to aggrandize the adsorption proficiency. Typical cases there are Cu(I) or Ag(I), the metals that were firstly reported for the π-complexation function between the metal sites and π orbitals of thiophenic molecule.19,20 Therefore, lots novel desulfurizers modified with Cu(I) or Ag(I) have been developed to attain higher sulfur uptake capacity and selectivity. For example, Khan et al. noticed that MIL-100-Fe, after adulterated with Cu(I) has enhanced adsorption toward BT. Inspired by the discovery they further inquired into the benefits brought by the formation of π-complex formation.17 Similar cases that accomplished by the same group of investigating the adsorption of BT onto π-complexing adsorbents (Cu(I)-doped MILs materials) were available.17,21 It is worth noting that in their work Cu(I) was successfully loaded into MIL-100(Fe) in a clement manner and a facile way


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to add in the Cu(I) part without reducing the Cu(II) species was also reported.21 In our previous work, a renewable MOF-5 (containing Zn(II)) adsorbent for the dibenzothiophene (DBT) capture from model fuels was successfully developed.22 Cu(I)/MOF-5 composites were prepared by spontaneous monolayer dispersion through adding diverse amounts of CuCl. Despite consequential decreasing of the adsorption capacity of BT in the existence of benzene, the MOF-5, due to the presence of more sites on Cu(I), still performed an excellently in adsorption. The surface area and pore volume reduced sharply due to Cu(I) loading, which could reduce the adsorption and diffusion properties of sulfur molecules in the pore channel. As mentioned before, for Cu-BTC, it is difficult to further improve the sulfur uptake capacity only through the effectiveness of unsaturated Cu(II) ions in the Cu-BTC. To tackle this issue, the valence change of Cu is worth investigation. As known from the literature, the Cu(II) ions could be reduced to Cu(I) by the V(III) ions at ambient temperature and pressure.23,24 In addition, extraordinary as it was regarded in the literatures, the impact of metal compositions on the adsorption desulfurization of Cu-BTC still has not been extensively searched.21,23,24 Therefore, in the present work, with the aim to open a new vision in this field, we provide experimental evidence of a method to metal ions modulation on Cu-BTC expecting to obtain a remarkable sorption affinity toward BT using different model fuels. By meticulously controlling the use of the reducing agent V(III), Cu(II) in the Cu-BTC structure was reduced to Cu(I) in a desirable manner at ambient temperature and pressure (Scheme S.I.1). In addition, the mechanism of using metal-modified Cu-BTC to capture BT


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was analyzed and discussed in this work, as well. 2.

EXPERIMENTAL SECTION

2.1. Chemicals. Reagents required include benzene tricarboxylic acid (H3BTC, 98%), cupric nitrate hydrate (Cu(NO3)2·3H2O, ≥99.5% ), benzene (≥99.5%), octane (≥99.5%), BT (≥ 99.5%), vanadium(III) chloride (VCl3, ≥ 99.9%), ethanol (>99.5%), and N,N dimethylformamide (DMF, ≥99.5%), all of which were supplied by Sigma–Aldrich Chemical Company. Every chemical selected in this work were employed without any purification. 2.2. Cu-BTC and V/Cu-BTC Preparation The Cu-BTC crystal was prepared through similar procedures in literatures.16,18 The V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC adsorbents were produced by following the Cu-BTC preparation process while using VCl3 as a reducing agent by the starting V/Cu molar ratio of 0.5:1, 1:1, and 1.5:1. To be specific, taking V1.0/Cu-BTC as an example, a blend of H3BTC (4.76 mmol), Cu(NO3)2·3H2O (4.14 mmol) and VCl3 (4.14 mmol) was dissolved in a 51 mL combination of 1:1:1 (v./v./v.) water, ethanol and N, N-Dimethylformamide, under 40 kHz ultrasound condition for 30 min at 25 oC. The above mixture was put in a Teflon autoclave and maintained at 85 oC for 20 h. After that the reactor was cooled down to 25 oC and a water-ethanol mixture was subsequently applied to remove any remained H3BTC from the blue powder. The purified product was achieved after filtration and dried at 100 oC for 5 h. 2.3. Samples Characterization


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Nitrogen adsorption-desorption experiments were carried out on a physical adsorption equipment (ASAP 2020) at −196 oC. The obtained N2 isotherm data is quite reproducible, whose error span is ±1%. The distribution of pore size was calculated from the isotherm data of desorption curve by means of the Nonlocal Density Functional Theory (NLDFT) theory. The SEM images was determined by electron microscope (Hitachi S4800). The samples’ crystal phase was considered by the XRD (D2 Phaser, Bruker, CuKα radiation). A Nicolet Nexus 470 spectrometer was employed to record the FT-IR data with potassium bromide pellet adsorbents. X-ray photoelectron spectroscopy (XPS) analysis was obtained by a Thermo Scientific ESCALAB 250Xi spectrometer. 2.4. Batch Adsorption Tests It is well known, most of practical fuels consist of about 20 wt % aromatic and 80 wt % aliphatic hydrocarbons.3,10,13 Therefore, utilizing benzene as the aromatic fuel (ARF) and n-octane as the aliphatic fuel (ALF), we prepared 3 characteristic model fuels. The mixed fuel (MIF) contains 20 wt % benzene and 80 wt % n-octane. We use BT to simulate the S-contaminant, dissolve it in the three kinds of fuels. The primary S-concentrations are 500~2000 µg/g for ALF, ARF and MIF, separately. Impurities and water were removed by degassing the adsorbents at 120 °C overnight under vacuum. The BT adsorption experiments were verified in a thermal Erlenmeyer flask which serves as the adsorption batch reactor and under atmospheric pressure with constant stirring. In the reactor with predestined time intervals, the adsorbent (0.05 g) was mixed with model fuel (100 g) for adsorption until it reaches equilibrium. The


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aqueous phase was then separated from the samples by filtration, and the S-content (initial and final S-concentrations) was detected by a gas chromatograph (GC-7890, Shanghai Science Instrument Co., China) containing with the FPD (hydrogen flame photometric detector) and an EC-5 capillary column (length=45 m; i.d.=0.30 m). The sulfur uptake capacity from the equipment is quite reproducible, which error span is ±1%. The sulfur uptake capacity was calculated by the formula (1) in the supporting information (Part IV(A)). 3. RESULTS AND DISCUSSION 3.1. Adsorbents Characterization The nitrogen adsorption-desorption isotherms and aggregated textural data of Cu-BTC and V/Cu-BTC adsorbents are presented in Figure 1 and Table S.I.1, correspondingly. According to the isotherms shape and IUPAC (International Union of Pure and Applied Chemistry) classification, the Cu-BTC and V/Cu-BTC materials are an amalgamation of typical I and IV16,18,25,26 with a hysteresis loop feature, illustrating the coexistence of micropores and mesopores. A high fraction of micropores in these MOFs can be observed from the steep ascending at the low pressure. While the increasing of mesoporous pores was confidently supposed from the hysteresis loop appears at P/Po of ∼0.4 which could result from the stacking pore formed by particles accumulation and MOFs crystal defect. Though the lesser porosity of all the MOFs materials (V/Cu-BTC) presented after modified by VCl3, the structure and morphology of the porosity were not visibly disturbed. The results of total pore volume and micropore are consistent with that of the surface area. Due to


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more V(III) introduced into the support, pores might be partly blocked and the BET surface area decreases. In order to determine the metal composition, V/Cu-BTC was revealed by XPS characterization (Figure 2(A)). Like the parent Cu-BTC,16,18 V/Cu-BTC exhibits the identical binding energy at 935.0 eV, matching to Cu(II) 2p3/2. As known from Figure 2(B), compared with the valence states of V in VCl3 and VOSO4, the V elements in V/Cu-BTC and VOSO4 display the uniform binding energy at 935.0 eV, which correspond to V(IV). The valence peak of the V element in V/Cu-BTC (Figure 2(C)) shows V(III) and V(IV) binding energy at 517.3 and 516.5 eV, which indicates that the redox reaction ( Cu2 + + V 3+ → Cu+ + V 4+ ) might occur during the hydrothermal synthesis of MOFs. There are similar research results in the literatures.25,26,27 The XRD curves of Cu-BTC and V/Cu-BTC materials are presented in Figure 3. The characteristic patterns of the Cu-BTC and V/Cu-BTC are very alike, which is consistent with the earlier works.25,26 This result specifies that the redox reaction process is isomorphous replacement and crystal structure of MOFs is kept undamaged under the employed circumstances. Meanwhile Cu species can be believed to present in new crystal form or attached to the framework with the practice of Cu(I) and Cu(II) because there are no any new peak displays in the pattern. More information of properties of functional groups on the Cu-BTC and V/Cu-BTC is exhibited by FT-IR results in Figure S.I.1. The typical Cu–O stretching vibration can be observed at 730 cm−1, which indicated that the oxygen atom was synchronized with Cu. In additon, a quite broad peak at 3423 cm−1 advised that H2O


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molecules are slackly bound with the adsorbents. The distinguished suggestions of these feature peaks are the stretching VC=O, VC–O and bending O–H vibrational frequencies at 1645, 1373 and 1444 cm−1, correspondingly, specifying the existence of a carboxylic acid group. The spectrum data of V/Cu-BTC is good conformed to Cu-BTC in the literatures.16,18,27 The SEM images in Figure 4(A) and (B) revealed that V/Cu-BTC material is not, ostensibly in macroscopic scale, diverse from the primary Cu-BTC. It validated that the crystal morphology has a consistent octahedron with about 10~20 µm in width, which was not disturbed by the redox reaction. 3.2 BT adsorption isotherms The adsorption isotherm curves of BT over Cu-BTC and V/Cu-BTC samples in ALF, ARF and MIF were detailed and presented in Figure 5(A), (B) and (C), accordingly. In each case of three model fuels, V/Cu-BTC sorbents yield higher adsorption amount of BT than Cu-BTC does due to the π-complexation reaction of Cu(I) and BT, but the uptake capacities are does not proportionate with the loading quantity of V(III). This non-linear result could be a consequence of variations in the structure and composition of the V/Cu-BTC surface, or unreachability to the Cu adsorption sites for some domains. It was found while the V/Cu molar ratio of 0.5:1, the sulfur adsorption capacity of V0.5/Cu-BTC, compared with the Cu-BTC has significantly increased, can be reasonably ascribed to π-complexation between BT and Cu(I). The content of active sites in Cu(I) was further increased by raising the V/Cu molar ratio and this lead to better sulfur uptake capacity of V1.0/Cu-BTC than


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Cu-BTC. Nevertheless, further increasing the doping content of V/Cu onto the support would indeed clog the pore and thus aggravate diffusion resistance in the mass transfer process, which could consequently result in the decreasing of available active metal sites that react with BT. This inevitable limitation accounts for the lower sulfur uptake capacity of higher V/Cu ratio (V1.5/Cu-BTC) than other V/Cu-BTC materials. Therefore, among all the samples, V1.0/Cu-BTC shows the uppermost desulfurization capacity. As known from Table S.I.2, sulfur capacities of the V/Cu-BTC sorbents were parallel or more outstanding than those of some other sorbents reported previously.18,22,23,27-34 In addition, the obtained experimental equilibrium adsorption data are then fitted using Langmuir, Freundlich, Temkin and D-R isotherm models by Eqs. (2)-(5) in the supporting information (Part IV(B)). The calculated constants according to these isotherm equations along with R2 values (standard deviation) in ALF, ARF and MIF are presented in Table S.I.3-5. This table shows that the adsorption process tallies best with the Langmuir isotherm with a R2＞ 0.99. The satisfied fittings to the Langmuir equation model suggest that this is a monolayer adsorption process on a comparatively homogeneous surface. Another special finding that should be noticed is that V/Cu-BTC sorbents display better desulfurization performance for ARF than for ALF and MIF. For instance, the maximal uptake capacity of the V1.0/Cu-BTC is 80 mg/g for ARF, while the resultant values reduce to 62 and 69 mg/g for ALF and MIF regarding the sulfur element. This funding is extremely strange, which is inconsistent with the related reported in the literatures.18,19,20 We have repeated and double checked our experiments and the


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adsorption results were highly consistent. There are possible two reasons for the above phenomenon. Firstly, there are three size-types of channel cavities with 0.35, 0.50, and 0.90 nm in the Cu-BTC structure.8 Synthetic Cu-BTC and V/Cu-BTC have the molecular-sieving windows of nominal diameter 0.35, 0.50, and 0.90 nm in its crystal lattice framework. Isooctane (kinetic size, length: 0.69 nm; width: 0.38 nm) could selectively enter two channel cavities of 0.90 and 0.50 nm during the adsorption process, while benzene (kinetic size: 0.60 nm) could only enter the cavity of 0.90 nm. Secondly, due to larger molecular mass, the isooctane might have more motion inertia than benzene during the mass transfer process, which could cause the isooctane molecule to occupy the adsorption sites of the MOFs.9,24,27 Thus, compared with benzene, isooctane might have a stronger competitive ability towards BT during the adsorption process. 3.3 BT adsorption kinetics The BT model fuels containing the adsorbents were mixed together with magnetic stirring for a fixed period of adsorption time (5–60 min) at 25 oC and ambient temperature. The influence of contact time on BT uptake capacity of as-prepared MOFs in ALF, ARF and MIF are shown in Figure 6 (A), (B) and (C), correspondingly. These figures showed that the BT uptake capacities accreting along with the prolonging of adsorption time, and the adsorption equilibrium time is about 30 min. These figures also show that quick increase in BT uptake capacity is reached within the first 10 min. The fast adsorption process at the initial stage might be due to the availability of the unadsorbed surface area and the remaining active metal sites.


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The kinetic adsorption data of BT, calculated from Equation (6), (7) and (8) in the supporting information (Part IV(C)), were correlated by pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models. The R2 values and calculated constants of the three kinetic equations in ALF, ARF and MIF are offered in Table S.I.6-8. when applying the pseudo-first model, considerable discrepancy between the experimental and calculated uptake capacity values displays. Nevertheless, high R2 values (0.99) are gotten with the linear plot of t/qt versus t, indicating the BT adsorption process in agreement with the pseudo-second order kinetic models. Based on intra-particle diffusion model and Figure S.I.2 (A), (B) and (C), the BT amount adsorbed (qt) versus the square root of time (t1/2) was not linear and the straight lines did not pass through the origin. The results suggested that the more than one adsorption process of BT onto V/Cu-BTC took part in, and the the rate-limiting step is not depended on intra-particle transport. Such finding is conformed to previous works.8,18,35 3.4. Reusability of V/Cu-BTC After batch adsorption equilibrium, the V1.0/Cu-BTC was impregnated in ethanol with magnetic agitation for 4 h and solid-liquid separation, and then the particles was put in a quartz tube furnace at 200 oC for 4 h in the atmosphere of nitrogen. After five cycles regeneration, the BT adsorption isotherm in MIF of regenerated V1.0/Cu-BTC was then recovered again. The results manifest that 90% more sulfur uptake capacities of regenerated V1.0/Cu-BTC is than the initial values (Figure S.I.3). The color of V1.0/Cu-BTC is black when it is soaked with BT while it displays its original blue


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color after regeneration. The insignificant decreasing of the desulfurization efficiency of BT can probably be ascribed to the leaching of the MOFs. Then the surface area, pore structure data, and XRD tests were carried out again. The results revealed that the pore volume and surface area after regeneration were well matched and analogous, which shows that the MOFs could be effortlessly regenerated after the adsorption desulfurization process and recycled at least five rounds. The different absorption mechanism of BT over Cu-BTC and V/Cu-BTC could be explained by the acid–base interaction and π-complexation. Based on Pearson’s hard and soft acid−base theory, the BT acting as soft bases are strongly attracted to the Cu(II) and Cu(I) (soft Lewis acid) over the adsorbent. In additon, π-complexation is also identified as one of the most commonly accepted mechanisms for adsorption desulfurization. The intimate interaction between cations of d-block metals and the thiophenic sulfur molecules, which is realized through π-complexation makes a contribution to enhance the adsorption proficiency. The most effective metal ion for π-complexation is Cu(I). V(III) was introduced as a reducing agent to reduce the Cu(II) in the framework of Cu-BTC to Cu(I). Therefore, due to existence of Cu(II) and Cu(I), V/Cu-BTC could be explained by the acid–base interaction and π-complexation. However, BT adsorption onto Cu-BTC only might depend on acid–base interaction. Comparison with Cu-BTC, the synergistic action of acid–base interaction and π-complexation might enhance the regenerative performance of V/Cu-BTC. Our experimental results also indicated the V/Cu-BTC is quite stable, which remains more than 90 % of sulfur capacity after 5 regeneration cycles by ethanol wash. Similar research results can be


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found in the literatures.18,27,36 4. CONCLUSIONS BT capture performances of Cu-BTC and V/Cu-BTC are assessed through batch tests. Experimental data demonstrated that the V1.0/Cu-BTC exhibited the highest sulfur uptake capacity in the adsorption desulfurization process, which can be attributed to the presence of Cu(I). The V/Cu-BTC exhibits a significantly higher BT uptake capacity compared with some other adsorbents in the literatures. Adsorption kinetics of the BT capture process complies with the pseudo-second-order model. Adsorption equilibrium data are better described by Langmuir than those of Freundlich, Temkin and D-R isotherm model equations. In general, V/Cu-BTC has been established to possess prospective value in deep desulfurization field.

ASSOCIATED CONTENT

Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: Part I: Oxidation reduction mechanism (Scheme S.I.1); Part II: Textural properties of Cu-BTC and V/Cu-BTC (Table S.I.1), Sulfur uptake capacity of different adsorbents (Table S.I.2), Constants and correlation coefficients of different adsorption models in ALF, ARF and MIF (Table S.I.3-5), Kinetic parameters in ALF, ARF and MIF for BT adsorption on Cu-BTC and V/Cu-BTC (Table S.I.6-8); Part III: IR spectra of Cu-BTC and V/Cu-BTC (Figure S.I.1), Weber–Morris intra-particle diffusion plots for the adsorption of BT in the ALF, ARF and MIF over Cu-BTC and


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V0/Cu-BTC (Figure S.I.2 (A), (B) and (C)); and Reusability of V/Cu-BTC (Figure S.I.3); Part IV: Sulfur uptake capacity calculation formula (1); Langmuir, Freundlich, Temkin, and D-R isotherm models equations (2)-(5); Adsorption kinetic equations (6)-(8). AUTHOR INFORMATION *,†E-mail: [email protected]. Fax: +86-579-82282325.Tel:+86-579-82282269.

ACKNOWLEDGMENTS We thank to the Zhejiang Provincial Natural Science Foundation of China under

Grant No. LY16B060002 and Open Research Fund of Key Laboratory of the Ministry of Education for Advanced Catalysis Materials and Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces, Zhejiang Normal University

REFERENCES

(1) Guo, J. S.; Chen, R. R.; Zhu, F. C.; Sun, S. G.; Villullas, H. M. New understandings of ethanol oxidation reaction mechanism on Pd/C and Pd2Ru/C catalysts in alkaline direct ethanol fuel cells. Appl Catal B-Environ 2018, 224, 602−611. (2) Domenico, C.; Melissa, S.; Valentina, C.; Stefano, L.; Giovanni, S.; Valerio, V. Biodegradable passion fruit-like nano-architectures as carriers for cisplatin prodrug. Part. Part. Syst. Charact. 2016, 33, 818−824. (3) Wu, K.; Wu, Y.; Chen, Y.; Chen, H.; Wang, J. Heterogeneous catalytic conversion of biobased chemicals into liquid fuels in the aqueous phase. Chem Sus Chem 2016, 9, 1355−1385.


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(4) Wei, H. H.; Zhang, Q.; Wang, Y.; Li, Y. J.; Fan, J. C.; Xu, Q. J.; Min, Y. L. Baby diaper-inspired construction of 3D porous composites for long-term lithium-ion batteries. Adv. Funct. Mater. 2018, 28, 1704440−1704452. (5) Wang, X. F.; Tang, Y. H.; Shi, P. H.; Fan, J. C.; Xu, Q. J.; Min, Y. L. Self-evaporating

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cobalt nanofibers

oxide for

high-performance lithium ion batteries. Chem. Eng. J. 2018, 334, 1642−1649. (6) Mostafa, M. S.; Betiha, M. A.; Rabie, A. M.; Hassan, H. M.; Morshedy, A. S. New conduct in the adsorptive removal of sulfur compounds by new nickel-molybdenum adsorbent. Ind. Eng. Chem. Res. 2017, 57, 425−433. (7) Tran, D. T.; Palomino, J. M.; Oliver, S. R. J. Desulfurization of JP-8 jet fuel: challenges and adsorptive materials. RSC. Adv. 2018, 8, 7301−7314. (8) Dai, W.; Gong, R.; Hu, J.; Zhou, L. M. Thiophene capture by an oxidation-modified activated carbon derived from bergamot. Sep. Sci. Technol. 2014, 49, 367−375. (9) Dehghan, R.; Anbia, M. Zeolites for Adsorptive desulfurization from fuels: a review. Fuel Process. Technol. 2017, 167, 99−116. (10) Wu, L.; Xiao, J.; Wu, Y.; Xian, S.; Miao, G.; Wang, H.; Li, Z. A combined experimental/computational study on the adsorption of organosulfur compounds over metal–organic frameworks from fuels. Langmuir 2014, 30, 1080–1088. (11) Zhang, Z. Q.; Cui, M.; Wang, F.; Zhou, T.; Zhang, G. D.; Wang, X. F. Synthesis, characterization, and adsorptive desulfurization behavior of merrifield resin supported


Page 17 of 27 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

Energy & Fuels

polymeric ionic liquids with different alkyl chain lengths. Colloid. Polym. Sci. 2017, 295, 1863−1871. (12) Khan, N. A.; Jhung, S. H. Adsorptive removal of benzothiophene using porous copper-benzenetricarboxylate loaded with phosphotungstic acid. Fuel Process. Technol. 2012, 100, 49−54. (13) Ren, X. L.; Liu, Z. W.; Dong, Lei.; Miao, G.; Liao, N.; Li, Z.; Xiao, J. Dynamic Catalytic adsorptive desulfurization of real diesel over ultra-stable and low-cost silica gel-supported TiO2. AIChE J. 2018, 64, 2146−2159. (14) Khan, N. A.; Hasan, Z.; Jhung, S. H. Adsorptive removal of hazardous materials using metal-organic frameworks (MOFs): A Review. J. Hazard. Mater. 2013, 244–245, 444−456. (15) Khan, N. A.; Jhung, S. H. Remarkable adsorption capacity of CuCl2-loaded porous vanadium benzene dicarboxylate for benzothiophene. Angew. Chem. Int. Ed. 2012, 51, 1198−1201. (16) Chui, S. S. Y.; Lo, S.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. A chemically functionalizable nanoporous material. Science 1999, 283, 1148−1150. (17) Khan, N. A.; Jhung, S. H. Low-temperature loading of Cu+ species over porous metal-organic frameworks (MOFs) and adsorptive desulfurization with Cu+-loaded MOFs. J. Hazard. Mater. 2012, 237−238, 180−185. (18) Wang, T. T.; Fang, Y. Y.; Dai, W.; Hu, L. F.; Ma, N.; Yu, L. The remarkable adsorption capacity of zinc/nickel/copper-based metal–organic frameworks for thiophenic sulfurs. RSC. Adv. 2016, 6, 105827−105832.


Energy & Fuels 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

(19) Yang, R. T.; Hernández-Maldonado, A. J.; Yang, F. H. Desulfurization of transportation fuels with zeolites under ambient conditions. Science 2003, 301, 79−81. (20) Hernández-Maldonado, A. J.; Yang, R. T. Desulfurization of diesel fuels by adsorption via π-complexation with vapor-phase exchanged Cu(I)−Y zeolites. J. Am. Chem. Soc. 2004, 126, 992−993. (21) Khan, N. A.; Kim, C. M.; Jhung, S. H. Adsorptive desulfurization using Cu-Ce/metal-organic framework: improved performance based on synergy between Cu and Ce. Chem. Eng. J. 2016, 311, 20−27. (22) Dai, W.; Hu, J.; Zhou, L. M.; Li, S.; Hu, X.; Huang, H. Removal of dibenzothiophene with composite adsorbent MOF-5/Cu(I). Energy Fuels 2013, 27, 816−821. (23) Khan, N. A.; Jhung, S. H. Effect of central metal ions of analogous metal-organic frameworks on the adsorptive removal of benzothiophene from a model fuel. J. Hazard. Mater. 2013, 260, 1050−1056. (24) Khan, N. A.; Jhung, S. H. Adsorptive removal and separation of chemicals with metal-organic frameworks: contribution of π-complexation. J. Hazard. Mater. 2017, 325, 198−213. (25) Sun, H.; Han, X.; Liu, K. F.; Shen, B. X.; Liu, J. C.; Wu, D.; Shi, X. Y. Metal-modified Cu-BTC acid for highly enhanced adsorption of organosulfur species. Ind. Eng. Chem. Res. 2017, 56, 9541−9550. (26) Sun, Z. G.; Li, G.; Zhang, Y.; Liu, H.; Gao, X. H. Ag–Cu–BTC prepared by


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postsynthetic exchange as effective catalyst for selective oxidation of toluene to benzaldehyde. Catal. Commun. 2015, 59, 92−96. (27) Dai, W.; Tian, N.; Liu, C. M.; Yu, L.; Liu, Q.; Ma, N.; Zhao, Y. X. (Zn, Ni, Cu)-BTC functionalized with phosphotungstic acid for adsorptive desulfurization in the presence of benzene and ketone. Energy Fuels 2017, 31, 13502−13508. (28) Li, W. L.; Xing, J. M.; Xiong, X. C.; Huang, J. X.; Liu, H. Z. Feasibility study on the integration of adsorption/bioregeneration of pi-complexation adsorbent for desulfurization. Ind. Eng. Chem. Res. 2006, 45, 2845−2849. (29) Wang, J.; Xu, F.; Xie, W. J.; Mei, Z. J.; Zhang, Q. Z.; Cai, J.; Cai, W. M. The enhanced adsorption of dibenzothiophene onto cerium/nickel-exchanged zeolite Y. J. Hazard. Mater. 2009, 163, 538−543. (30) Srivastav, A.; Srivastava, V. C. Adsorptive desulfurization by activated alumina. J. Hazard. Mater. 2009, 170, 1133−1140. (31) Nejad, N. F.; Shams, E.; Amini, M. K.; Bennett, J. C. Ordered mesoporous carbon CMK-5 as a potential sorbent for fuel desulfurization: application to the removal of dibenzothiophene and comparison

with CMK-3. Microporous

Mesoporous Mater. 2013, 168, 239−246. (32) Shi, Y.; Zhang, X.; Wang L.; Liu, G. MOF-derived porous carbon for adsorptive desulfurization. AIChE J. 2014, 60, 2747−2751. (33) Song, X. L.; Sun, L. B.; He, G. S. Isolated Cu(I) sites supported on β-cyclodextrin: an efficient π-complexation adsorbent for thiophene capture. Chem. Commun. 2011, 47, 650−652.


Energy & Fuels 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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(34) Khan, N. A.; Jun, J. W.; Jeong, J. H. Remarkable adsorptive performance of a metal-organic

framework,

vanadium-benzenedicarboxylate

(MIL-47),

for

benzothiophene. Chem. Commun. 2011, 47, 1306−1308. (35) Yu, L.; Liu, Q.; Dai, W.; Tian, N.; Ma, N. Efficient thiophene capture with a hydrophobic Cu-BTC-(n)Br adsorbent in the presence of moisture. Microporous Mesoporous Mater. 2018, 266, 7−13. (36) Sun, H.; Han, X.; Liu, K. F.; Shen, B. X.; Liu, J. C.; Wu, D.; Shi, X. Y. Metal-modified Cu-BTC acid for highly enhanced adsorption of organosulfur species. Ind. Eng. Chem. Res. 2017, 56, 9541−9550.


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Figure Captions: Figure 1. N2 adsorption/desorption isotherms for Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC samples at -196 oC, respectively. Figure 2. Cu 2p and V 2p XPS spectra of V1.0/Cu-BTC. (A): Cu 2p; (B): V 2p; (C): V 2p3/2 Figure 3. XRD analysis for Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC samples. Figure 4. SEM images of Cu-BTC and V1.0/Cu-BTC samples. (A): Cu-BTC; (B): V1.0/Cu-BTC. Figure 5. Adsorption isotherms of BT in the ALF, ARF and MIF over Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC, respectively. (A): ALF; (B): ARF; (C): MIF. Figure 6. Effect of contact time on the adsorption capacity of BT in the ALF, ARF and MIF over Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC at 25 oC and ambient pressure. (A): ALF; (B): ARF; (C): MIF.


Energy & Fuels

320

3

Volume adsorbed (cm /g, STP)

400

240

Cu-BTC V0.5/Cu-BTC V1.0/Cu-BTC V1.5/Cu-BTC

160

80

0 0.0

0.2

0.4

0.6

0.8

1.0

Relative pressure (P/P0)

Figure 1. N2 adsorption/desorption isotherms for Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC samples at -196 oC, respectively.

(A)

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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CuCl V1.0/Cu-BTC Cu(NO3)2 CuCl2

970

960

950

940

Binding energy(eV)


930

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Intensity(a.u)

(B)

VOSO4 V1.0/Cu-BTC VCl3

535

530

525

520

515

Binding energy (eV)

8000

(C) 4+

V 7000

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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3+

V 6000

5000

4000

3000 528

526

524

522

520

518

516

514

Binding energy (eV)

Figure 2. Cu 2p and V 2p XPS spectra of V1.0/Cu-BTC. (A): Cu 2p; (B): V 2p; (C): V 2p3/2


Energy & Fuels

V1.5/Cu-BTC

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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V1.0/Cu-BTC

V0.5/Cu-BTC

(440) (333) (422)

(222) (400) (220)

6

8

10

12

14

16

18

20

Cu-BTC

22

24

26

28

30

32

2-Theta (degree)

Figure 3. XRD analysis for Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC samples. (A)

(B)

Figure 4. SEM images of Cu-BTC and V1.0/Cu-BTC samples. (A): Cu-BTC; (B): V1.0/Cu-BTC.


Page 25 of 27

70

(A): ALF 60

qe (mg/g)

50

40

30


20

10

0 0

200

400

600

800

1000

1200

1400

Ce (ppm)

90

(B): ARF

80 70

qe (mg/g)

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

Energy & Fuels

60 50 40


30 20 10 0 0

200

400

600

800

1000

Ce (ppm)


1200

1400

Energy & Fuels

70

(C): MIF

60

qe (mg/g)

50

40

30


20

10

0 0

200

400

600

800

1000

1200

1400

Ce (ppm)

Figure 5. Adsorption isotherms of BT in the ALF, ARF and MIF over Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC, respectively. (A): ALF; (B): ARF; (C): MIF.

70

(A): ALF 60

50

qt (mg/g)

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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40

30


20

10

0 0

10

20

30

40

50

t (min)


60

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90

(B): ARF

80 70

qt (mg/g)

60 50 40


30 20 10 0 0

10

20

30

40

50

60

t (min)

70

(C): MIF

60

50

qt (mg/g)

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

Energy & Fuels

40

30


20

10

0 0

10

20

30

40

50

60

t (min)

Figure 6. Effect of contact time on the adsorption capacity of BT in the ALF, ARF and MIF over Cu-BTC, V0.5/Cu-BTC, V1.0/Cu-BTC, and V1.5/Cu-BTC at 25 oC and ambient pressure. (A): ALF; (B): ARF; (C): MIF.


Highly Efficient Benzothiophene Capture with a Metal-Modified Cu

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