Adsorptive Denitrogenation of Model Fuel with CuCl-Loaded

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Adsorptive Denitrogenation of Model Fuel with CuClloaded Adsorbents: Contribution of #-complexation and Direct Interaction between Adsorbates and Cuprous Ions Nazmul Abedin Khan, Nizam Uddin, Cheol Ho Choi, and Sung Hwa Jhung J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 16 May 2017 Downloaded from http://pubs.acs.org on May 18, 2017

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The Journal of Physical Chemistry

Adsorptive Denitrogenation of Model Fuel with CuCl-loaded Adsorbents: Contribution of Πcomplexation and Direct Interaction between Adsorbates and Cuprous Ions Nazmul Abedin Khan, Nizam Uddin, Cheol Ho Choi, and Sung Hwa Jhung* Department of Chemistry and Green Nanomaterials Research Center, Kyungpook National University, Daegu 41566, Korea

Abstract Removing nitrogen-containing compounds (NCCs) from fuel is very important to protect the environment and catalysts in various processes, including hydrodesulfurization. In this study, the

adsorptive

denitrogenation

(ADN)

of

quinolines

(such

as

quinoline,

1,2,3,4-

tetrahydoquinoline, and decahydroquinoline) was studied in a systematic way using a CuClloaded metal–organic framework (here MIL-100(Cr)) and activated carbon in order to understand ADN quantitatively. In this study, it was found that CuCl was effective for ADN via π-complexation and direct interaction, and the important role of Cu(I) in ADN could be defined. Quinolines with aromaticity could interact with Cu(I), mainly via π-complexation. However, quinolines without aromaticity interacted with Cu(I) through direct interaction (or basic N-Cu(I)). This direct interaction was only meaningful when there was no aromaticity in the NCCs; the ADN efficiency via direct interaction was relatively low (around 30% of π-complexation 1 ACS Paragon Plus Environment


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between the simple aromatic ring and Cu(I)). An aromatic ring containing nitrogen was more effective (by around 50%) than a simple aromatic ring (without nitrogen) in π-complexation.

1. Introduction Nitrogen-containing compounds (NCCs) are usually present in crude fuel at very low levels. Recently, there has been a significant demand to reduce these NCCs in commercial fuel to very low levels in order to reduce air pollution due to the emission of various nitrogen oxides and deactivation of numerous catalysts.1-3 NCCs, especially prior to hydrodesulfurization (HDS), should be removed from fuels because they also hamper the catalytic HDS by competing with various sulfur-containing compounds (SCCs) for the active sites and eventually reducing the catalytic activity.1-2 Moreover, coal-derived liquid fuels contain very high quantities of basic NCCs, including aniline, quinoline (QUI) and their derivatives.4 Therefore, NCCs, particularly basic NCCs, should be removed before commercialization because fuels derived from coal are expected to be extensively utilized in the near future. Various techniques including hydrodenitrogenation,5 adsorption,1-2 and extraction6 have previously been utilized to remove NCCs from fuels. Adsorption is considered as one of the most effective methods, specifically in terms of attaining an ultralow nitrogen content and easy operation. Porous adsorbents, including activated carbon (AC),2, 7 zeolite,8-9 mesoporous silica,10 Ti-HMS,11 and metal oxide,12 have been investigated for the adsorptive removal of NCCs. It has been widely reported that metal ions such as Cu(I), Ag(I), Pt(II), and Pd(II) form πcomplexes with aromatics and olefins.13-17 Therefore, porous adsorbents having π-complexing metal ions are capable of π-complex formation for the efficient adsorption/separation of various aromatic organics, including NCCs, from liquid fuel in a flat and facedown manner.14, 18 For example, Cu(I)-incorporated porous materials such as carbon19 and zeolite8 have been studied for 2 ACS Paragon Plus Environment

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the adsorption removal of NCCs. Aromatic NCCs (such as quinolines) have a lone pair of electrons on the nitrogen. Therefore, they can act either as n-type donors by donating the lone pair of electrons (weak bases) to the adsorbent (direct N-M (metal) interaction)9 or as p-type donors by using the π-electrons of the aromatic ring of the adsorbent to form π-complexes.8, 19-21 Thus far, π-complexation has been explained to adsorb various aromatics, including NCCs; however, to the best of our knowledge, there has been no report or experimental result that quantitatively estimated the contributions of the π-electrons and hetero-atoms in the adsorption of NCCs. Moreover, the contribution of a direct interaction (for example, interaction between the Cu(I) and N of NCCs) in a vertical way has not been detailed, even though such an interaction was suggested as a mechanism for the adsorption of NCCs (especially basic NCCs).9 So far, remarkable progress in the development of various porous materials has been achieved because of the development of advanced functional materials,14, 22-27 including metal– organic framework (MOF) type materials.28-38 The usefulness of MOFs is derived from their huge porosity and the facile tunability of the pore size and shape (from the micro- to mesoporous scale) by changing the connectivity of the metal center and the organic linkers.39 Recently, MOF-type materials have also been studied for the adsorption/removal of numerous hazardous materials.29, 40-47 The denitrogenation of liquid fuel has also been widely performed with MOFs3, 48-56. Modified MOFs have been reported for the efficient adsorption of NCCs via πcomplexation,21 H-bonding,54, 57-59 and acid-base interactions.51, 60 However, a more fundamental understanding of the high/efficient uptake of NCCs, with functionalized or modified MOF adsorbents, is required not only for competitive applications but also for further improvements in the adsorption of NCCs.

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In this study, CuCl particles, as Cu(I) species, were introduced within a highly porous MOF via the reduction of CuCl2 at room temperature with the help of Na2SO3. Among the numerous MOFs reported, porous chromium-benzenetricarboxylate (MIL-100(Cr)),61 which is one of the most commonly studied MOFs for various potential applications, including adsorption,50, 62-63 was applied in this study. The preferential electronic interactions between three quinolines and the Cu(I) of the adsorbents were systemically studied. QUI, 1,2,3,4-tetrahydroquinoline (tetraQUI), and decahydroquinoline (deca-QUI) were adsorbed onto Cu(I)-based adsorbents in order to understand the contribution of π-complexation (between the Cu(I) and π-electrons of the adsorbates) and direct interaction (between the Cu(I) and N of adsorbates). In order to confirm the interaction between the Cu(I) and quinolines, CuCl-loaded AC was also applied for the adsorption. To the best of our knowledge, this is the first experimental study to show quantitatively the role of electrons (on the quinoline ring or lone pair on N) in the adsorption of quinolines over a Cu(I)-loaded MOF or AC. 2. Experimental 2.1. Materials Cupric chloride (CuCl2) and sodium sulﬁte (Na2SO3) were obtained from Acros Organics and Kanto Chemicals Co., respectively. Granular activated carbon (AC, size: 2–3 mm) was purchased from Duksan Pure Chemicals Co. Ltd. Chromium (VI) oxide and n-octane were purchased from Junsei Chemical Company. Hydrofluoric acid (HF, 48.0%) and hydrochloric acid (HCl, 35%) were purchased from OCI Company Ltd. Quinoline (C9H7N, 98%), deca-QUI (C9H17N, 97%), and trimesic acid (H3BTC) were obtained from Sigma-Aldrich Co. Ltd. The tetra-QUI (C9H11N, 99%) was purchased from Alfa-Aesar Co. The chemicals used in this study were analytical grade and applied without further purification. 4 ACS Paragon Plus Environment

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2.2. Synthesis and modification MIL-100(Cr) was synthesized under an autogenous pressure to follow the reported methods.50 For the synthesis mixture, H3BTC, chromium (VI) oxide , H2O, and HF were mixed with a molar ratio of 1:0.67:265:1 and then transferred to a Teflon-lined autoclave. The sealed autoclave was heated in a conventional electric oven at a temperature of 220 °C for 96 h. The obtained solid was purified by mixing with ethanol and stirring for 5 h at 65 °C, followed by filtering, washing, and drying. The CuCl-loaded MIL-100(Cr) was prepared similar to a reported method21 with Na2SO3 as a reductant. Exact amounts of MIL-100(Cr) (1.0 g) were taken to glass vials containing 2.5, 5.0, 10.0, and 20.0 mL of a 0.2 M CuCl2 aqueous solution and magnetically stirred at room temperature for 30 min. The same amounts (2.5, 5.0, 10.0, and 20.0 mL) of a 0.1 M Na2SO3 aqueous solution were added dropwise under stirring to the respective CuCl2 solutions containing MIL-100(Cr). The final mixture was allowed to stir for 20 min, and then sulfurous acid solution (1 mL) was added. Sulfurous acid solution was prepared by mixing 0.2 M HCl (3.0 mL) and 0.25 mM Na2SO3 (25.0 mL). The MIL-100(Cr)-containing mixture was filtered and further washed with sulfurous acid solution. The solids were dried overnight at 100 °C using a vacuum oven (to avoid air contact). The adsorbents were called CuCl(x)/MIL100(Cr), where x represents the volume of the CuCl2 or Na2SO3 solution employed in the preparation per 1 g of MIL-100(Cr). CuCl-incorporated activated carbon adsorbents were also prepared following steps very similar to those mentioned for the preparation of the CuCl(x)/MIL100(Cr). The experimental details for the characterization and adsorption processes are also given in the Supporting Information (SI). 2.3. Theoretical methodology 5 ACS Paragon Plus Environment


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The geometries of the quinoline-Cu(I) complexes were optimized at the MP2/cc-pVTZ level of theory. The GAMESS64 program was used to optimize the stable geometry of compounds and their relative energies in gas phase. After optimization with MP2/cc-pVTZ level the quinolines-Cu(I) bond energies (BEs) were calculated using the following formula: Q + Cu(I) = Q-Cu(I), where Q = Quinoline, tetra-QUI, or deca-QUI. BE is defined as the standard-state energy change for the reaction at a specified temperature, here at 298 K was obtained by the following:

+ Cu+ N

N Cu+

BE = EQ-Cu(I) – (EQ + ECu(I)) The detailed procedure of bond energy and pKb calculation are given in the SI. 3. Results and discussion 3.1. Properties of adsorbents The crystal structure of the obtained MOF was confirmed to be MIL-100(Cr), as shown by the XRD patterns in Figure S1a.61 Figure S1 shows that there was no noticeable change in the XRD patterns of MIL-100(Cr) and AC after the introduction of the CuCl species. The nitrogen adsorption isotherms and textural properties of the studied adsorbents are shown in Figure S2 and Table 1, respectively. The surface area and pore volume of the modified adsorbents decreased with the loading of the CuCl species, indicating the existence of some guest materials supported on the virgin MIL-100(Cr) or AC adsorbents. The presence of CuCl species in the CuCl(5.0)/MIL-100(Cr) adsorbent was confirmed via an energy dispersive spectroscopic


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analysis (EDS) (Table 1). Figure S3 (EDS mapping) shows that the CuCl species were dispersed well onto the porous support. As shown in Figure S4, the oxidation state of the incorporated copper in the CuCl(10.0)/MIL-100(Cr) or CuCl(10.0)/AC was confirmed to be +1. The copresence of Cu2+ (together with Cu+, even in very low amount) in the CuCl(10.0)/AC might be because of partial oxidation throughout the synthesis procedure including storage. It is quite well-known that +1 oxidation state of copper is very sensitive to air and unstable; therefore, may be oxidized or disproportionated into Cu2+ and Cu0 in the presence of moisture or air.65 3.2. Adsorption results CuCl/adsorbents were prepared from various amounts of metal precursors (see experimental section). The optimum CuCl contents in the porous MIL-100(Cr) were determined prior to detailed experiments to ensure the maximum adsorption capability of the CuCl-loaded MIL-101(Cr) for QUI. As shown in Figure 1, the QUI and tetra-QUI adsorption capacity increased with an increase in the amount of CuCl precursors up to a certain level, demonstrating the favorable effect of CuCl on the adsorption processes. The adsorption of quinolines over the pristine MIL-100(Cr) is mainly because of van der Waals interactions or simple pore filling. Another possible reason of the adsorption might be because of π-π interaction66 between aromatic ring of the MOF and aromaticity of quinolines. The possible contribution of π-π interaction in the adsorption can be understood based on the fact that the adsorbed quantity of quinolines decrease in the order QUI > tetra-QUI > deca-QUI (Figure 1). As shown in Figure 1, the optimum composition for the loaded CuCl was determined to be 5.0 mL of the CuCl precursor (based on 1.0 g of MIL-100(Cr)). However, the MIL-100(Cr) samples with higher CuCl contents (>5.0 mL) showed lower adsorbed amounts, probably due to the excessively high degree of pore filling with CuCl particles. In other words, there might be a 7 ACS Paragon Plus Environment


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tradeoff between the beneficial role (see below) of CuCl in the adsorption of QUI or tetra-QUI and decreasing porosity (with increasing CuCl). Therefore, the amount of CuCl on the porous support materials could not be increased much, and further experiments on quinoline adsorption were conducted with only virgin MIL-100(Cr) and CuCl(5.0)/MIL-100(Cr). Interestingly, as illustrated in Figure 1, in contrast with the QUI or tetra-QUI adsorptions, the adsorption of decaQUI using the CuCl-supported MIL-100(Cr) samples decreased monotonously with an increase in the content of CuCl in MIL-100(Cr), suggesting a negative role for CuCl in the adsorption of deca-QUI. To better determine the effect of CuCl (in MIL-100(Cr)) on the adsorption process, all three quinolines were adsorbed over the virgin and most effective MOF [CuCl(5.0)/MIL-100(Cr), which showed the highest adsorption for QUI] over various times up to 12 h (Figure 2). CuCl(5.0)/MIL-100(Cr) showed higher amounts of adsorbed QUI and tetra-QUI than virgin MIL-100(Cr) for all the adsorption times. However, CuCl(5.0)/MIL-100(Cr) poorly adsorbed deca-QUI and resulted in lower adsorption capacities than virgin MIL-100(Cr) for all the adsorption times. Therefore, the results in Figure 2 generally agree with those in Figure 1. To calculate the maximum adsorption capacities (Q0) of the virgin and supported MOF (CuCl(5.0)/MIL-100(Cr)), adsorptions were performed using the three quinoline solutions with a wide range of initial concentrations. The adsorption isotherms (shown in Figure 3) of the virgin and modified adsorbents were obtained after adsorption for a sufficiently long time of 12 h. The general trend in the adsorption isotherms shown in Figure 3 matches the results illustrated in Figures 1 and 2. The adsorption isotherms were plotted (see Figure S5) to follow the Langmuir equation, and the obtained Q0 values of the adsorbents are summarized in Table 2. With the incorporation of CuCl, the Q0 values increased from 395 to 485 mg/g and from 222 to 235 mg/g


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for the adsorption of QUI and tetra-QUI, respectively. However, the presence of CuCl in MIL100(Cr) reduced the Q0 value from 149 to 127 mg/g for the adsorption of deca-QUI. A non-MOF adsorbent (AC) was also employed to check the adsorption trend obtained for the adsorption of the quinolines with CuCl-supported MIL-100(Cr). CuCl(5.0)/AC was prepared in a way very similar to that used to prepare the CuCl(5.0)/MIL-100(Cr) adsorbent. Similar to the experimental results obtained with the CuCl/MIL-100(Cr) samples, the CuClsupported AC also adsorbed higher amounts of QUI and tetra-QUI compared to bare AC (Figure 4). However, the CuCl-supported AC adsorbed a smaller amount of deca-QUI than AC. Therefore, the supporting materials (AC and MIL-100(Cr)) for CuCl loading did not have a great impact on the adsorption of the three quinolines. In other words, the beneficial role of the loaded CuCl, when a suitable amount was supported, for QUI and tetra-QUI was observed in both the CuCl/AC and CuCl/MIL-100(Cr); however, a negative effect was found for deca-QUI adsorption. 3.3. Quantitative analyses of adsorptions All of the adsorption results (in Figures 1–4 and Tables 2 and 3) show that the loaded CuCl (on MIL-100(Cr) and AC) increased the adsorbed quantity when the NCCs had aromatic rings (QUI and tetra-QUI); however, an opposite tendency was observed when there was no aromaticity in the adsorbate (deca-QUI). The beneficial role of CuCl in the adsorption of NCCs (with aromaticity) was understandable based on the π-complexation8, 19 between the π-electrons (on aromatic rings) and Cu(I). However, it was not easy to explain the negative role of CuCl in the adsorption of the non-aromatic NCC (deca-QUI). To obtain a better understanding of the adsorptions of quinolines, the qt and Q0 values were calculated on the basis of the unit surface areas (rather than the unit weights) of the adsorbents because the surface area of an adsorbent is one of the most important factors for 9 ACS Paragon Plus Environment


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controlling the adsorption, especially when there is no particular interaction mechanism.67 As listed in Table 2, the Q0 values (based on the surface areas of the adsorbents) of MIL-100(Cr) for QUI, tetra-QUI, and deca-QUI were increased by 202, 81, and 26 µg/m2, respectively, by the incorporation of the CuCl species into the MOF. Therefore, CuCl had a beneficial effect on the adsorption of quinolines, irrespective of the aromaticity/basicity. This was understandable because Cu(I) may interact effectively with NCCs (irrespective of aromaticity/basicity) in several ways.9 To gain a better understanding of the interactions between the Cu(I) and N of the NCCs, the structures of the Cu(I)-NCC complexes were optimized theoretically (Figures S6 and S7). The bond energies of the Cu(I) and N of the NCCs were calculated using the second-order Møller–Plesset (MP2) theory. As shown in Figure S8, the bond energies follow the order decaQUI >> tetra-QUI > QUI. The trend of the bond energies can be effectively explained by the basicities of the studied quinolines (see Figure S8). The increase of 26 µg/m2 for deca-QUI by CuCl might be explained by the direct interaction between the Cu(I) and N of deca-QUI (since there are no π-electrons on deca-QUI for π-complexation) based on the favorable/direct interaction between the basic NCCs and Cu(I).9 On the other hand, the increase (81 µg/m2) for tetra-QUI by CuCl might be mainly because of an aromatic ring for π-complexation between the Cu(I) and π-electrons (on aromatic rings). The contribution of the direct interaction between the Cu(I) and N of tetra-QUI might be relatively low because the basicity of N on tetra-QUI is quite low (pKb=9.068-69), compared with that of deca-QUI (pKb ~ 0.37, theoretically calculated), and direct interaction might be more favorable with an increase in the basicity of the NCCs. The increase of 202 µg/m2 for QUI by CuCl might be divided into two π-complexations [between the Cu(I) and π-electrons from the benzene ring (similar to tetra-QUI, 81 µg/m2) and from the


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hetero-ring containing N (121 µg/m2)]. Therefore, the hetero-ring of QUI might be more important (by around 50%) than the simple benzene ring in π-complexation with Cu(I). The adsorbed quantities for quinolines after adsorption for 12 h (q12 h) were also compared (Table 3). The q12 h results for the quinolines are similar to the Q0 values in Table 2. In other words, the increase in the deca-QUI adsorption by CuCl (loaded on MOF) via direct NCu(I) interaction is 14 µg/m2; the increases by CuCl via π-complexation with the benzene ring and hetero ring are 60 and 83 µg/m2, respectively. Thus, the contribution of the direct interaction between the Cu(I) and N (even with a basic property, pKb ~ 0.37) is relatively small, and that of the π-complex between the hetero-ring and Cu(I) is larger than that for the benzene ring and Cu(I). The q12 h values for the adsorption of quinolines with pristine and CuCl-loaded ACs are also compared in Table 3. Very similar to the adsorption with the MIL-100(Cr) samples, the use of CuCl on AC enhanced the adsorption of deca-QUI by 15 µg/m2 via a direct N-Cu(I) interaction. From the adsorption of tetra-QUI and QUI over CuCl/AC, it could be confirmed that π-complexes between the Cu(I) and benzene ring resulted in a q12 h increase of 47 µg/m2; the 82 µg/m2 increase in q12

h

might be due to the interaction between the Cu(I) and hetero ring.

Therefore, the current results observed with CuCl/AC were in fairly good agreement with the results obtained with CuCl/MIL-100(Cr). The adsorption paths (which also show the relative importance of interactions in the adsorption of NCCs) for the adsorption of quinolines with active Cu(I) sites are summarized in Scheme 1. 4. Conclusion The following conclusions can be obtained based on the adsorption of quinolines over CuCl-loaded MIL-100(Cr) (or AC). First, CuCl was effective in adsorbing NCCs via two 11 ACS Paragon Plus Environment


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methods (direct interaction between N and Cu(I), and π-complexation between the aromatic rings and Cu(I)). Second, the efficiency of direct interaction was quite low (~30% compared to πcomplexation) for ADN and meaningful only when there was no aromaticity in the NCCs. Third, π-complexation was very effective in ADN when there were aromatic rings on the NCCs. Fourth, aromatic rings containing nitrogen were more effective (by ~50%) than aromatic rings without nitrogen for π-complexation in ADN.


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ASSOCIATED CONTENT Supporting Information. Supporting Information Includes detailed synthesis, adsorption method and calculation and additional adsorption and theoretical calculation data. “This material is available free of charge via the Internet at http://pubs.acs.org.” AUTHOR INFORMATION Corresponding Author *Sung Hwa Jhung, Phone: 82-10-28185341; Fax: 82-53-950-6330; E-mail: [email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ACKNOWLEDGMENT This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and future Planning (grant number: 2015R1A2A1A15055291). ABBREVIATIONS ADN, adsorptive denitrogenation; NCC, nitrogen containing compounds; SCC, sulfur containing compounds; HDS, hydrodesulfurization; QUI, quinoline; tetra-QUI, 1,2,3,4-tetrahydroquinoline; deac-QUI, decahydroquinoline; AC, activated carbon; BE, bond energy. REFERENCES 13 ACS Paragon Plus Environment


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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


QUI

tetra-QUI N

N

N

deca-QUI N π-complex (horizontal) Cu(I)

π-complex (horizontal) Cu(I)

π-complex (horizontal) Cu(I)

N-Cu(I) interaction (vertical)

Cu(I)

Scheme 1. Mechanisms for the adsorption of quinolines over Cu(I)-loaded adsorbents. Both πcomplexation and direct N-Cu(I) interaction are shown, and length and thickness of blue lines mean the relative strength of interactions.



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

Page 24 of 31

Table 1. Textural properties and Cu contents of studied adsorbents. MIL100(Cr)

CuCl(2.5)/MIL -100(Cr)

CuCl(5.0)/MI L-100(Cr)

CuCl(10.0)/MIL100(Cr)

AC

CuCl(5.0)/ AC

SBET, m2/g

1653

1311

1093

702

1032

817

PV (mic.), cm3/g

0.35

0.34

0.31

0.23

0.30

0.23

PV (tot.), cm3/g

0.91

0.64

0.62

0.47

0.59

0.46

Cu, wt% *

0.00

0.68

0.94

1.83

ND**

ND**

* **

based on EDS analysis. Not determined.


Page 25 of 31

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


Table 2. Maximum adsorption capacities (Q0) for the adsorption of quinolines with the adsorbents.* Q0, MIL-100(Cr)

Q0, CuCl(5.0)/MIL100(Cr)

∆, Based on adsorbent weight**, mg/g

∆, Based on unit surface area of the adsorbents*, µg/m2

mg/g

µg/m2

mg/g

µg/m2

QUI

395

238

485

440

90

202

tetra-QUI

222

134

235

215

13

81

deca-QUI

149

90

127

116

-22

26

*

∆ means the increased Q0 with the incorporation of Cu. The values obtained by Q0 of CuCl(5.0)/MIL-100(Cr) - Q0 of MIL-100(Cr)

**



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

Page 26 of 31

Table 3. q12 h for the adsorption of quinolines with the adsorbents.* The initial concentration of quinolines was 1000 µg/g. q12 h of MIL100(Cr)

q12 h of CuCl(5.0)/MIL100(Cr)

∆, mg/g

mg/g

µg/m2

mg/g

µg/m2

QUI

219.3

132.7

301.1

275.5

81.8

tetraQUI

135.7

82.1

155.4

142.2

decaQUI

111.2

67.3

88.9

81.4

∆, µg/m2

q12 h of AC

q12 h of CuCl(5.0)/AC

∆, mg/g

∆, µg/m2

mg/g

µg/m2

mg/g

µg/m2

143.0

166.1

160.9

236.4

289.4

70.3

129.0

19.7

60.1

101.3

98.2

118.2

144.7

16.9

46.5

-22.3

14.1

85.1

82.5

80.0

97.9

-5.1

15.4

*

∆ values obtained by q12 h of CuCl(5.0)/MIL-100(Cr) - q12 h of MIL-100(Cr)

or, q12 h of CuCl(5.0)/AC - q12 h of AC


Page 27 of 31

300 250 q 12 h, 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


QUI tetra-QUI deca-QUI

200 150 100 50 0

5

10

15

20

Amount of CuCl precursor (mL) loaded on 1 g of MIL-100(Cr)

Figure 1. Effect of CuCl content, loaded on MIL-100(Cr), on the adsorption of QUIs.



350

(a) 300

qt, mg/g

250 200 150 100

MIL100-Cr CuCl(5.0)/MIL-100(Cr)

50 0 0

2

4

6

8

10

12

Time, h

200

120

(b)

(c) 100

150

qt, mg/g

80 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

Page 28 of 31

100


40


50

60

20 0

0 0

2

4

6

8

10

12

0

2

Time, h

4

6

8

10

12

Time, h

Figure 2. Effect of contact time on the adsorption of (a) QUI, (b) tetra-QUI and (c) deca-QUI with the virgin and CuCl-supported MIL-100(Cr)s. The initial concentrations of quinolines were 1000 µg/g.


Page 29 of 31

(a)

400

Q0, mg/g

300

200 MIL100-Cr CuCl(5.0)/MIL-100(Cr)

100

0 0

500

1000

1500

Ce, ppm

150

250

(c)

(b) 200 100 Q0, mg/g

150 Q0, 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


100 MIL100-Cr CuCl(5.0)/MIL-100(Cr)

50

50


0

0 0

500

1000

0

1500

500

1000

1500

Ce, ppm

Ce, ppm

Figure 3. Adsorption isotherms for the adsorption of (a) QUI, (b) tetra-QUI and (c) deca-QUI with the virgin and CuCl-supported MIL-100(Cr)s.



250

200 AC CuCl(5.0)/AC q 12 h, 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

150

100

50

0 QUI

tetra-QUI

deca-QUI

Figure 4. Adsorption of quinolines with AC and CuCl-supported AC. The initial concentrations of quinolines were 1000 µg/g.


Page 30 of 31

Page 31 of 31

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TOC Graphic


Adsorptive Denitrogenation of Model Fuel with CuCl-Loaded

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