An Efficient Extraction Method for Separation of Carbazole and

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Efficiency and Sustainability

An Efficient Extraction Method for Separation of Carbazole and Derivatives from Coal Tar Derived Anthracene Oil by Using Ionic Liquids Yi-Feng Chen, Zhi-Min Zong, Xue-Ke Li, Guang-Hui Liu, Zheng Yang, Xian-Gang Jiang, Fangjing Liu, Xian-Yong Wei, Qing-Jie Guo, tiansheng zhao, Hong-Cun Bai, and Baojun Wang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02675 • Publication Date (Web): 30 Oct 2018 Downloaded from http://pubs.acs.org on November 3, 2018

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An Efficient Extraction Method for Separation of Carbazole and Derivatives from Coal Tar Derived Anthracene Oil by Using Ionic Liquids Yi-Feng Chena, Zhi-Min Zonga,*, Xue-Ke Lia, Guang-Hui Liua, Zheng Yanga, Xian-Gang Jianga, Fang-Jing Liua, Xian-Yong Weia,b, Qing-Jie Guob, Tian-Sheng Zhaob, Hong-Cun Baib, Bao-Jun Wangc a

Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education, China University

of Mining & Technology, Xuzhou 221116, Jiangsu, China b

State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, Ningxia

University, Yinchuan 750021, Ningxia, China c

Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province,

Taiyuan University of Technology, Taiyuan 030024, Shanxi, China ABSTRACT Carbazole and its derivatives are important value-added chemicals in anthracene oil (AO) which is one of the coal tar fractions. Green and efficient carbazole purification process is a critical step in carbazole utilization. In this work, imidazolium-based ionic liquids (ILs) were used as novel extractants to extract carbazole from AO, and the effects of different anionic substituents and cationic structures on the separation of carbazole were investigated. The results show that the yield and purity of carbazole dramatically reached up to 96.2% and 98.0% by extracting anthracene oil-related model oil with ILs, respectively. The hydrogen-bond force existing between 1-butyl-3-methylimidazolium dicyanamide (ILa) and carbazole was revealed by FTIR and 2D NMR, and further confirmed by density functional theory simulation results. Such π-π interaction and hydrogen bonds formed between ILs and carbazole play crucial roles in the efficient separation of carbazole from AO. Simultaneously, the stability test ACS Paragon Plus Environment

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shows that ILa is easily recyclable and highly stable for the separation of carbazole. Moreover, the yield and purity of carbazole extracted from real AO were 66.6% and 90.2% with ILa as the extractant by assistance with flash chromatograph. This study provides a green and efficient approach for separating high value-added chemicals from coal tar and its derived fractions. Keywords: Carbazole, Anthracene oil, Ionic liquids, Molecular simulation, Hydrogen bond 1. INTRODUCTION Nowadays, along with aggravating situation of environmental pollution and dwindling reserves of fossil fuels, much attention has been paid to developing efficient and clean separation processes of fine chemicals. The products derived from anthracene oil (AO) have the potential to be significant contributors for obtaining high-grade electrode materials and value-added chemicals1. AO is a mixture obtained by the distillation of coal tar, mainly composed of polycyclic aromatic hydrocarbons with 2-5 aromatic rings2. Carbazole, mainly derived from coal tars, is an important nitrogen-containing organic compound (NCOC) raw material for chemical production. The larger conjugated system and strong intramolecular electron transfer of carbazole, make it play a significant role, in the production of dyes and pigments3, pesticides4 and medicine5, photovoltaic materials6, synthetic resins7, supramolecular recognition8, and so on. However, it is difficult to obtain from the petroleum industry conveniently and economically, mainly relying on the extraction from AO. Thus, the optimization of carbazole extraction technology is essential for the efficient utilization of AO. Components in AO can be broadly classified as low-acidic, alkaline, neutral and aromatic compounds because of their high complexity9. Correspondingly, four representative components (i.e., carbazole, quinoline, fluorene, and anthracene) were selected to make up anthracene oil-related model

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oil (MO). Effective separation of carbazole by π-π interaction and hydrogen bonds has been a big challenge due to the weaker N-H···N bond binding energy (13-40 kJ mol-1)10. The selective separation of specific nitrogen-containing functional groups in AO ingredients not only embodies the concept of atomic economy, but also combines with the green energy. Carbazole was used as a model compound for revealing the mechanisms of extraction. Carbazole separation methods can be divided into two major categories: physical methods (including solvent crystallization11, distillation, emulsion liquid membrane12 and supercritical fluid extraction13, etc.) and chemical methods (sulfuric acid method and alkali metal method). However, distillation method is limited by coking due to high temperature and plate numbers and usually combined with solvent crystallization. Emulsion liquid membrane has the deficiencies in the preparation of the emulsion and the stability of membrane system. Moreover, severe operating conditions adversely affect the application of zone smelting. Compared to physical methods, chemical methods have been abandoned due to wastewater pollution. Solvent crystallization is the method most used in industries currently with defect of using toxic solvents. Thus, an environmentally benign and highly efficient separation method is necessary for full use of carbazole in AO. Ionic liquids (ILs), composed of organic cations and inorganic anions, have received widespread attention as green solvents14, especially in the field of separation and synthesis. Compared with organic solvent extraction, ILs have great advantages in nonvolatility, stability, selectivity, low vapor pressure and environmental friendliness15-17. Low vapor pressure allows the dissolved components to be recycled again by simple distillation or back-extraction. A variety of functional groups in the chemical structure of ILs make it relatively easy to form hydrogen bonds, p-π, σ-π, CH-π, π-π and so on, with the specific components in the oil18. Moreover, ILs and oils do not dissolve each other, which can ACS Paragon Plus Environment

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effectively prevent cross-contamination19. Therefore, it is possible to separate specific components in AO by ILs. At present, ILs have been widely used in the fields of electrochemical, polymer synthesis and separation, especially for desulfurization and denitrogenation of fuels20,21 and the separation of value-added components in oils (e.g., phenolic, NCOCs and aromatics)22-24. Hou et al.23 studied the effect of different anions and cations for ILs on the phenol extraction. Zhang et al.25 selectively separated aromatics from paraffins and cycloalkanes using morpholinium-based ILs. Measurement and correlation of phase equilibria were also applied to the separation of mixed systems by ILs26-28. Various studies have shown that liquid-liquid separation of carbazole from AO using ILs is feasible and environmentally friendly29-31. In this work, imidazolium-based ILs (IBILs) were used as new extractants to separate carbazole from AO. The effects of different anionic substituents and cationic structures of IBILs were discussed. Meanwhile, different experimental conditions were optimized. The formation of hydrogen bonds between IBILs and carbazole enables the extraction process to be achieved, which was revealed by FTIR and 2D NMR, and further confirmed by density functional theory (DFT) simulation results. ILs showed good performance in the stability test. Simultaneously, ILa was chosen for further investigation in real AO, assisted by flash chromatograph, which provided a green and efficient approach for separating high value-added chemicals from coal tar and its derived fractions. 2. EXPERIMENTAL 2.1. Materials In the experiment, all reagents were purified by distillation prior to use. All the ILs were dried in vacuum at 150 oC before use (Table S1). AO was collected from Wugang Group Co., Ltd., China. ACS Paragon Plus Environment

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Silica gel (SG, 200-300 mesh) was purchased from Shanghai Chemical Co., Ltd., China, and activated before use. 2.2. Preparation of MO Four representative components: carbazole, quinoline, fluorene and anthracene were selected to prepare MO. The mass ratios of these four components in MO referred to their mass fraction in real AO. 1 g carbazole, 1 g quinoline, 3 g fluorene and 5 g anthracene (1: 1: 3: 5) were dispersed in 40 mL mixed solution of toluene and acetone. A small amount of acetone (2 mL) was added into MO to avoid the phase splitting due to the dissolving capacity of carbazole. The mixture was stirred to form a homogeneous system. Representatives of MO were prepared according to the literature9, and other different MO concentrations (MOCs) were also prepared in the same way. 2.3. Extraction and recovery procedure in MO As shown in Figure 1, a certain amount of ILs was added into the aforementioned round bottom flask with prepared MO and stirred at the set temperature for a stipulated period of time. After keeping in thermostat for some time, obvious stratification would occur, and the upper (U1) and lower (L1) phases were separated carefully. In addition, 40 mL carbon tetrachloride (CCl4) was added into L1 as the back-extractant to separate the components of U1, which may be slightly soluble in L1. Therefore, stratification would occur again, namely the upper (U2) and lower (L2) phases. Then, 80 mL distilled water was added into U2 as the other back-extractant to obtain filtered carbazole (FC). The filtrate was distilled by rotary evaporator until the mass was constant to obtain the recovered ILs. The mass of FC and recovered ILs were weighed accurately after vacuum drying. All the experiments were repeated three times and the average value was adopted. ACS Paragon Plus Environment

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2.4. Separation procedure of carbazole in real AO As illustrated in Figure 2, the AO sample (500 g) and CCl4 (1000 mL) were sonicated in a magnetically stirred extractor with ultrasonic apparatus. CCl4 can selectively remove some non-polar aromatics. The residue (R1) was extracted by ethyl acetate (EA, 1000 mL), therewith, 1 g of the extraction liquid (E2) after concentration was packed in a 5 g silica gel column. EA/Hex mixed solvent (volume ratio 1:2) was chosen as mobile phase in flash chromatograph. Detection was performed with two UV detectors, UV1 (254 nm) and UV2 (365 nm), and the flow rate was 30 mL min-1 corresponding to the column volume. Fractions were injected into the tubes in turn and analyzed by GC/MS. The fraction enriched with carbazole (Fc) was further extracted with an IL under the optimal experimental conditions. 2.5. Sample analysis Peak area normalization method was adopted to complete semi-quantitative analysis of the compounds to obtain the relative content of them with GC/MS, while external standard method was adopted to complete quantitative calculation of the detected compounds. FTIR analyses of fresh and regenerative ILs were carried out by using KBr compression method to scan in the range of 400-4000 cm-1. 1H NMR was adopted to analyze the purity of recovered ILs using DMSO-d6 as an external reference at 297 K. 2.6. Calculation of yield and purity The concentration of each component and the volume in initial MO, U1, and the solution dissolved from FC were recorded as C0i, C1i, C2i (mg mL-1), and V0, V1, V2 (mL), respectively. The extract yield


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(YE, %) was calculated by Eq. (1), and the extract purity (PE, %) was calculated by Eq. (2). The specific formulas for calculation were as follows: 𝐶2𝑖 ∙ 𝑉2

𝑌E (%) = 𝑚0𝑖 𝑃E (%) =

∙ 𝑃0𝑖 %

𝐶2𝑖 ∙ 𝑉2 𝑚2

× 100

× 100

(1) (2)

Where P0i and m0i (mg) represent the purity and the mass of initial components, respectively. m2 represents the mass of FC. The above formulas are applicable to calculation of the yield and purity in real AO. 3. RESULTS AND DISCUSSION 3.1. Effects of anions and cations in ILs Different electronegativity and space extension of anions, as well as the structure of cations in ILs have varying degrees of impact on extraction. The coordination between the cation and the anion is the main factor that affects the extraction process of carbazole. Therefore, this paper explored the best combination of cation and anion for IBILs, and the name, code, structure, molar mass, melting point, density and water content of IBILs used in the experiment were listed in Table S2. High stability of IBILs makes it suitable for the thermal extraction and back-extraction conditions32. In order to clearly reflect the extraction capacity of ILs itself, the procedure of back-extraction by CCl4 was not applied. IBILs were researched in this paper including ILa, ILb, ILc, and ILd, and all the experiments were performed under the same conditions. As shown in Figure 3, different anionic substituents had a certain influence on the extraction procedure. The yield of carbazole followed this order: ILa > ILb > ILc > ILd, while the purity of carbazole followed this order: ILa > ILd > ILb > ILc. Among IBILs, ILa exhibited the best extraction performance for separating carbazole with yield and purity of 81.0% and 76.3%, ACS Paragon Plus Environment

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respectively. This could be attributed to the larger stretching space of the anion in ILa than in other IBILs. Solute molecules are hard to enter in the ILs with compact structures to complete structure reorganization and hence it makes the extraction of solute molecules more difficult33. As exhibited in Figure 4, the carbon number in alkyl chain of the cation has a significant influence on the carbazole extraction process. For ILs with same anions but different cations, the yield of carbazole decreases in the order: BMI > EMI > OMI. On the one hand, the higher yield of carbazole in ILa than that in 1-ethyl-3-methylimidazolium dicyanamide could be due to the increase of the carbon number in alkyl chain, enlarging the enclosed solute space between the cation and the anion. The lower compactness allows the attack of the solute molecules to complete the restructuring, and thereupon it has a higher capacity for the dissolved components33. On the other hand, the lower yield of carbazole in 1-Octyl-3-methylimidazolium dicyanamide than that in ILa could result from the steric hindrance of longer alkyl chain which would weaken the hydrogen bond interaction and increase the distance between the charge centers of the cation and the anion. Thus, the appropriate distance between the cation and the anion (i.e., suitable carbon number in alkyl chain) for the formation of hydrogen bonds is important for promoting the yield of carbazole. In addition, anionic substituents show greater effects than cationic structures on the carbazole extraction. Meanwhile, the coordination of the cation and the anion is a major factor affecting carbazole extraction process. Hence, based on the excellent performance on the yield and purity of carbazole, ILa was utilized as the extractant in the succeeding experiments. 3.2. Effects of experimental conditions As demonstrated in Figure 5a, the yield of carbazole increases sharply with increasing reaction time


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from 5 to 30 min, while further prolonging time increases the yield slightly, indicating that 30 min is sufficient for extracting most of carbazole in MO. Therefore, subsequent tests were all performed at 30 min. During extraction, carbazole dissolved in U1 rapidly migrated into ILs phase. In this study, the two phases were delaminated in a short time. The purity was stable at ca. 98% through the back-extraction with CCl4, suggesting that CCl4 is a promising solvent for selectively purifying carbazole. As Figure 5b shows, the yield of carbazole increases slightly with increasing temperature from 293.15 K to 303.15 K. This may be due to the increase in temperature that accelerates the molecular motion, so that ILs could have more opportunity to contact with carbazole molecules. Subsequently, as the reaction temperature increases gradually in the range of 303.15 K to 333.15 K, the yield of carbazole continues to decline, yet the decreasing range is getting smaller. This trend may be caused by the increase of solubility for carbazole in toluene. Therefore, the appropriate reaction temperature can promote the extraction of carbazole by ILs. However, as the temperature continues to increase, the interaction between ILs and carbazole will be weakened. The maximum yield was ca. 80.9% at 303.15 K, and the corresponding purity was ca. 97.6%. Furthermore, 303.15 K was close to the room temperature, without additional heating. As shown in Figure 5c, the yield increases rapidly from ca. 61.3% to 94.6% in the mass ratio range of 1:8 to 1:1, while the yield increases slightly (from ca. 94.6% to 97.8%) when the mass ratio was 2:1. It should be noted that the purity was always maintained at a high level (around ca. 98%) regardless of the mass ratio. Therefore, high yield and purity were obtained when the mass ratio was high. Although the yield increased with the amount of ILs used, ILa/MO mass ratio of 1:1 was selected in view of cost and recycling. In fact, the content of carbazole in different types of AO was often different. Therefore, exploring ACS Paragon Plus Environment

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the impact of initial concentration for carbazole on the extraction reaction was necessary. As Figure 5d displays, the yield increases within low MOC, and then decreases as further increasing, but it remains over ca. 85% throughout. Therewith, the same trend occurs in the purity within high MOC. Obviously, excessively high concentration of carbazole is not conducive to ILs extraction. When the mass ratio was constant, as the initial concentration excessively increased, the amount of ILs cannot meet the extraction requirement of carbazole, and the yield decreased accordingly. The maximum yield may appear around 33 mg mL-1, where the yield and purity are above ca. 96% and ca. 98%, respectively. ILa exhibited significant extraction ability of carbazole from MO in a high range of initial concentration, therefore it can be potentially used in the separation of carbazole from real AO. Under the above optimized conditions, ILa was selected to carry out the extraction. The component change of MO in the extraction process was quantitatively analyzed with GC/MS, and Figure 6 shows the component of the initial MO, U1, and FC. By comparison, it can be found that the relative abundance of carbazole in U1 is substantially zero after extraction, indicating that ILa has high carbazole extractive efficiency. Moreover, the relative abundance of carbazole obtained by back-extraction was relatively high (76.25%), indicating that ILa also has high selectivity for carbazole extraction. In addition, the slightly solubility of U1 into ILa will lead to the relative abundance of carbazole not as high as expected34. But in this work, CCl4 was added into L1 as the back-extractant to extract the components of U1, which may be slightly soluble in L1. Therewith, the purity was increased to ca. 97.9%. 3.3. Separation of carbazole from real AO Based on the results of MO, ILa was used as the solvent for extraction of real AO to evaluate the


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suitability of ILs for industrial carbazole separation from highly complex mixtures. As illustrated in Figures S1-S4 and Tables S3-S31, in total 96 organic compounds were detected in E1-E3 and Fc, which can be classified into 29 categories. Among them, anthracene (RC 19.19% in E2) was selected as the representative of NSCAs, MNs, MAs, MPsI, MFI & MPsII, EAs, DMNs, DMPs and TMNs due to high content. Fluorene was also selected as the representative of F & BFs, MFsII and HAs. Similarly, carbazole (RC 16.56% in E2) was selected as the representative of C & BCs, MCs, ECs and DMCs. Meanwhile, quinoline was selected as the basic representative of NCOCs, such as IQs, Phenanthridines, Acridines and NNs, which cannot form hydrogen bonds with ILs. In view of the low RC and poor representation of oxygen-containing and sulfur-containing compounds (TRC 3.01% in E2), they were not selected as the representative. This can explain why compositions of MO were selected. However, no arenes, oxygen-containing and sulfur-containing compounds existing in E1 and E2 were detected in E3, suggesting good separation efficiency and high selectivity of ILa. As Figure 7 exhibits, the distribution of group components in E3 is substantially different from that in E1, E2 and Fc. For example, the total relative content (TRC) of NSCAs is predominantly high in E2, while E3 only contains C & BCs and a little part of MCs. Meanwhile, Phenanthridines and IQs consisting in Fc were not detected in E3, evidently indicating that ILa has strong capacity and selectivity for extracting compounds containing N-H bonds, consistent with the results of MO extraction as stated above. The RC of carbazole increased from 16.56% in E2 to 58.88% in Fc, and then significantly increased to 91.03% in E3, verifying that it is feasible to separate carbazole from real AO with high purity through extraction with ILa. Moreover, the yield can reach up to ca. 72.5% by flash chromatograph, as well as ca. 91.8% by ILs. Previous studies on extracting NCOCs by ILs were shown in Table S32. It can be found that there are few references in separation of nitrogen compounds from ACS Paragon Plus Environment

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real coal tar, and instead reports on denitrogenation of diesel and gasoline fields. By contrast, this paper has an exploratory significance for the application of ILs to the separation of real coal tar, and the result obtained is highly competitive. Further investigations focusing on optimization of extraction conditions and fine separation/purification processes will be conducted to promote the yield and purity of carbazole from AO. 3.4. Possible mechanism of extraction process Intermolecular interaction between the ILa and carbazole was studied to explain strong extraction capacity of ILa and high selectivity of carbazole. The π-π interaction was reported between aromatic hydrocarbons and ILs, whose cations are wrapped with aromatic solute in a so-called sandwich-like structure45,46. Likewise, this interaction exists between carbazoles and ILs. However, the interaction between carbazole and ILs is stronger than that between arenes and ILs because of the higher π-electron density of carbazole47. As demonstrated in Figure 8, the spectrum of the complex (ILa-carbazole) has a series of same characteristic absorption bands with that of fresh carbazole and ILa, suggesting that carbazole combines well with ILa under certain interaction. Compared with carbazole, the absorption intensity of the band around 3414 cm-1 assigned to the stretching vibration frequency of N-H9 is much weaker in the complex, indicating that carbazole molecules in the complex undergo a change in vibrational state. This further suggested the presence of hydrogen bonds between carbazole and ILa. HSQC spectra (Figure S5-7) can show the correlation peak between 1H nucleus and

13C

directly connected to it. With the formation of the complex, it can be found that 1H and

nucleus

13C

NMR

chemical shifts () of carbazole moved to the low field, with the great change in the hydrogen atom of


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N-H bond (Δ = 0.027 ppm) and C-H bond (Δ = 0.016 ppm). However, 1H and 13C NMR chemical shifts of ILs moved to the high field, especially, the

13C

chemical shift of C≡N bond decreased

significantly (Δd’ = -0.015 ppm). This fully demonstrates that hydrogen bond can be formed between N-H bond of carbazole and the nitrogen atom of ILs anion, and carbazole can also form π-π interaction with ILs cation, which are responsible for efficient extraction. It can also be seen from the variation of chemical shifts (Table S33 and S34) that hydrogen bonding is the main factor compared to π-π interaction. For the formation of X-H···Y hydrogen bond, the electron cloud surrounding the proton is affected by the atom Y, which deviates from the proton toward the atom X. Thereby, this reduces the electron cloud density around the proton, enhances the deshielding effect of the proton, and forces the formant of the proton to the low field, finally increasing the chemical shift. This was consistent with the conclusion of the FTIR analysis, and further demonstrates the existence of hydrogen bonds. In order to explain the intermolecular interaction thoroughly, the chemical bonds formed between carbazole and ILa were simulated using Gaussian 09W program in combination with DFT48. The geometry optimization of ILa, ILb and carbazole was first performed by means of M06-2X/ 6-311+G(d,p) basis set, and then mPW2PLYPD/ cc-pVTZ basis set for single-point energy (ele). Meanwhile, the calculated single-point energy was corrected by zero-point energy (Hcorr) to obtain the total enthalpy (H(T)). For ILa, many different spatial configurations can be formed when dicyanamide anion was located at different positions of cation. After optimization and frequency calculation, six stable configurations were identified and the most stable configuration was shown in Figure S849-51. In this case, the dicyanamide anion and the imidazole ring of the cation are coplanar, and the N29 and N30 atoms on the anion can form hydrogen bonds with the H17, H11 and H16 atoms on the cation (N29-H17 = 0.239 nm, N30-H11 = 0.238 nm, N30-H16 = 0.217 nm), respectively. The structural ACS Paragon Plus Environment

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formula and atomic number of ILa are shown in Figure 9. Under these circumstances, there are three possible approaches for carbazole molecules to form hydrogen bonds with the dicyanamide anion: N26, N29, and N30. However, it is difficult for carbazole molecules to form hydrogen bond with N30. On the one hand, the hydrogen on the methylene group is more active than that on the methyl group. The steric hindrance for carbazole molecules to form hydrogen bond with N30 is higher. On the other hand, N30 forms intramolecular hydrogen bonds with H11 and H16, simultaneously, which presents as a firm intramolecular structure. Thus, more energy is needed for carbazole molecules to destroy the existing intermolecular hydrogen bonds and to reform new hydrogen bonds with N30. These three approaches of hydrogen bond formation were simulated by Gaussian 09W program. As shown in Table 1, the hydrogen bond length will be slightly longer for hydrogen bond between carbazole and N29 than that between carbazole and N26. Meanwhile, the structure of coplanar dicyanamide anion and the imidazole ring has been reversed. Intermolecular hydrogen bond lengths of ILa will have a greater change compared to itself. Nevertheless, if the carbazole molecule forms hydrogen bond with N26, intermolecular hydrogen bond lengths will be shortened to a great extent, indicating the highest hydrogen bond strength. Moreover, it is more stable for the symmetrical structure formed by N26, which is considered as the optimized configuration. The shorter the hydrogen bond length, the stronger the hydrogen bonding interaction will be9. The interaction between carbazole and ILs is stronger than that between carbazole and the solvent, which promotes the efficient extraction of carbazole. As presented in Figure 10, the hydrogen bond formed between carbazole and N26 of ILa is shorter than that between carbazole and Cl- of ILb, which could be responsible for the higher yield of carbazole with ILa than that with ILb. Moreover, the enthalpy (ΔH) during hydrogen bond formation was calculated, and ΔH had gone through the zero-point correction, ACS Paragon Plus Environment

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which was calculated as follows: ∆𝐻(kJ mol ―1) = 2625.5 × [𝐻AB(Hartree) ― (𝐻A(Hartree) + 𝐻B(Hartree))] The HAB is the total enthalpy; HA and HB are the enthalpy of the single object. The greater the absolute value of ΔH, the more stable the structure is, the stronger the hydrogen bond is. Table 2 and Table 3 showed ΔH between ILs and carbazole. The theoretical calculation provided good insight into the interaction between ILs and carbazole. ΔH between ILa and carbazole was larger than that between ILb and carbazole, further confirming the experimental results. As Figure 11 shows, red indicates the area where negative charge exists and blue indicates the area where positive charge exists. The electron cloud density distribution reflects the distribution of charges around ILa-carbazole, clearly showing the sites where the interaction is easy to occur. Based on the analyses with FTIR and 2D NMR combined with simulation results, hydrogen bonds formed between ILa and carbazole during extraction play an important role in separating carbazole from AO. 3.5. Recovery and recycling of ILs ILs are considered as green and alternative solvents to replace traditional organic solvents, largely because ILs are easy to recycle, making it possible for a sustainable green separation. Distilled water was selected as the back-extractant to obtain carbazole, and then water was evaporated in a vacuum drying oven until the mass of ILs was constant to get recovered ILs. Therewith, the recovered ILs were repeatedly used for extraction under the same conditions. In this work, ILa was recycled for 3 times, then its recycling ratio and the corresponding yield of carbazole were shown in Figure 12. It is noted that recycling ratio of ILa maintained above 95% along with corresponding yield slightly decreasing to ca. 89.8% after recycled 3 times. Distributions of functional groups in recycled ILs are almost the same


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as those in the fresh ILs, according to analysis with FTIR as shown in Figure S9. As illustrated in Figure 13, the ratio of integral peak area in 1H NMR was in accordance with the atomic number ratio of hydrogen at different chemical shifts within the allowable error range. Moreover, there are no extra peaks in 1H NMR spectrum of recycled ILs, indicating the ILs were recycled successfully with high purity. 4. CONCLUSIONS In the work, a green and efficient separation process, ILs extraction assisted by flash chromatograph, was designed to separate carbazole from real AO in high yield and purity, which effectively avoided using toxic organic solvents and reduced environmental pollution. Self-compactness and steric hindrance were critical factors that led to significant differences in extraction capacity between IBILs with different anionic substituents and cationic structures. Under the optimum extraction conditions with ILa, the yield and purity of carbazole could reach 96.2% and 98.0% in MO, respectively. CCl4 is a promising and effective back-extractant to selectively purify carbazole. The hydrogen bonds formed between ILs and carbazole could play a crucial role in the extraction of carbazole from AO. FTIR and 1H

NMR studies revealed that the hydrogen-bond force exists between ILa and carbazole which was

also confirmed by DFT simulation results. ILa was easily recyclable with high purity and highly stable for the separation of carbazole. The new separation process of carbazole proposed in this study would be a potential candidate for the green and efficient production of high value-added chemicals from coal and its derived liquids. AUTHOR INFORMATION Corresponding Author ACS Paragon Plus Environment

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*Tel: +86 516 83885951. Fax: +86 516 83884399. E-mail: [email protected] (Z. M. Zong). Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This work was supported by the Key Project of Joint Fund from National Natural Science Foundation of China and the Government of Xinjiang Uygur Autonomous Region (Grant U1503293), the Key Project of Joint fund from National Nature Science Foundation of China and the Government of Shanxi Province (Grant U1610223), the Natural Scientific Foundation of China (Grant 21576280), the Natural Scientific Foundation of China (Grant 21776298), the National Key Research and Development Program of China (Grant 2018YFB06046002) and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. The authors greatly appreciate Prof. B. Wang (The Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology), who generously assisted us by using quantum chemistry calculation based on the Gaussian platform. NOMENCLATURE C0i

Concentration of each component in initial MO (mg mL-1)

C1i

Concentration of each component in U1 (mg mL-1)

C2i

Concentration of each component in FC solution (mg mL-1)

V0

Volume of initial MO (mL)

V1

Volume of U1 (mL)


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

V2

Volume of FC solution (mL)

P0i

Purity of initial components (%)

m0i

Mass of initial components (mg)

m2

Mass of FC (mg)

YE

Extract yield

PE

Extract purity

ele

Single-point energy (Hartree)

Hcorr

Zero-point energy (Hartree)

H(T)

Total enthalpy after correction (Hartree)

HAB

Total enthalpy of object AB (Hartree)

HA

Enthalpy of object A (Hartree)

HB

Enthalpy of object B (Hartree)

ΔH

Enthalpy (kJ mol-1)

ABBREVIATIONS AO

Anthracene oil

MO

Anthracene oil-related model oil

ILs

Ionic liquids

IBILs

Imidazolium-based ionic liquids

CCl4

Carbon tetrachloride

EA

Ethyl acetate

Hex

Hexane


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Energy & Fuels

TE

Thermal extraction

BE

Back-extraction

U1

Upper phase after extraction with ILs

L1

Lower phase after extraction with ILs

U2

Upper phase after extraction with CCl4

L2

Lower phase after extraction with CCl4

E1

Extract liquid after extraction with CCl4

R1

Residue after extraction with CCl4

E2

Extract liquid after extraction with EA

R2

Residue after extraction with EA

Fc

Fraction enriched with carbazole by flash chromatograph

E3

Extract liquid after extraction with ILs

FC

Filtered carbazole

MOC

Model oil concentration

NCOCs

Nitrogen-containing organic compounds

GC/MS

Gas chromatograph/mass spectrometer

FTIR

Fourier transform infrared spectrometer

HSQC

Heteronuclear single quantum coherence

1H

Nuclear magnetic resonance spectrometer

NMR

REFERENCES (1) Delport, M. R.; Badenhorst, H. Production of a self-adhering mesophase powder from anthracene


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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oil for low pressure forming of graphite artefacts. J. Mater. Sci. 2016, 51 (13), 6309-6318. (2) Liang, P.; Yu, J.; Zhang, Y. Q.; Jiao, T. T.; Qin, X. Z. Effects of natural dolomite catalysts on cracking anthracene oil. Energy Fuels. 2017, 31 (11), 11765-11772. (3) Gawale, Y.; Adarsh, N.; Kalva, S. K.; Joseph, J.; Pramanik, M.; Ramaiah, D. Carbazole-linked near-infrared Aza-BODIPY dyes as triplet sensitizers and photoacoustic contrast agents for deep-tissue imaging. Chem. Eur. J. 2017, 23 (27), 6570-6578. (4) Wang, W. S.; Li, Q.; Wei, Y. F.; Xue, J.; Sun, X.; Yu, Y. Novel carbazole aminoalcohols as inhibitors of -hematin formation: Antiplasmodial and antischistosomal activities. Int. J. Parasitol. Drug. 2017, 7 (2), 191-199. (5) Sherer, C.; Snape, T. J. Heterocyclic scaffolds as promising anticancer agents against tumours of the central nervous system: Exploring the scope of indole and carbazole derivatives. Eur. J. Med. Chem. 2015, 97 (32), 552-560. (6) Qureshi, M.; Chetia, T. R.; Ansari, M. S.; Soni, S. S. Enhanced photovoltaic performance of mesoporous SnO2 based solar cells utilizing 2D MgO nanosheets sensitized by a metal-free carbazole derivative. J. Mater. Chem. A. 2015, 3 (8), 4291-4300. (7) Mousawi, A. Al.; Dumur, F.; Garra, P.; Toufaily, J.; Hamieh, T.; Graff, B. Carbazole scaffold based photoinitiator/photoredox catalysts: toward new high performance photoinitiating systems and application in LED projector 3D printing resins. Macromolecules. 2017, 50 (7), 2747-2758. (8) Yang, Z. Z.; Chen, Y.; Li, G.; Tian, Z. M.; Zhao, L.; Wu, X. Supramolecular recognition of three way junction DNA by a cationic calix[3]carbazole. Chem. Eur. J. 2018, 24 (23), 1-8. (9) Jiao, T. T.; Zhuang, X. L.; He, H. Y.; Zhao, L. H.; Li, C. S.; Chen, H. N. An ionic liquid extraction process for the separation of indole from wash oil. Green Chem. 2015, 17 (7), 3783-3790. ACS Paragon Plus Environment

Page 21 of 41 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

(10) An, B. B.; Feng, S. Y.; Wen, K. K.; Wu, W. P.; Yuan, H. J.; Zhu, Q. L. Theoretical insights into the ultrafast excited-state intramolecular proton transfer (ESIPT) mechanism in a series of amide-based N-H···N hydrogen-bonding compounds. Org. Electron. 2017, 45, 1-8. (11) Ye, C. P.; Zheng, H.; Wu, T. T.; Fan, M. M.; Feng, J.; Li, W. Y. Optimization of solvent crystallization process in obtaining high purity anthracene and carbazole from crude anthracene. AIChE. J. 2014, 60 (1), 275-281. (12) Habaki, H.; Bi, D.; Shimada, Y.; Egashira, R. Enhancement of permeation rate of nitrogen heterocyclic compounds for emulsion liquid membrane separation of coal tar absorption oil. J. Chem. Eng. Jpn. 2014, 47 (3), 254-260. (13) Martinez, F.; Martin, A.; Camarillo, R.; Rincon, J. Measurement and modeling of the solubility of 9H-carbazole in sub- and supercritical propane. J. Chem. Eng. Data. 2011, 56 (4), 956-962. (14) Amde, M.; Liu, J. F.; Pang, L. Environmental application, fate, effects and concerns of ionic liquids: a review. Environ. Sci. Technol. 2015, 49 (21), 12611-12627. (15) Fadeev, A. G.; Meagher, M. M. Opportunities for ionic liquids in recovery of biofuels. Chem. Commun. 2001, 3, 295-296. (16) Poole, C. F.; Poole, S. K. Extraction of organic compounds with room temperature ionic liquids. J. Chromatogr. A. 2010, 1217 (16), 2268-2286. (17) Amado Alviz, P. L.; Alvarez, A. J. Comparative life cycle assessment of the use of an ionic liquid ([Bmim]Br) versus a volatile organic solvent in the production of acetylsalicylic acid. J. Clean. Prod. 2017, 168, 1614-1624. (18) Yang, Q. W.; Xing, H. B.; Su, B. G.; Bao, Z. B.; Wang, J.; Yang, Y. W. The essential role of hydrogen-bonding interaction in the extractive separation of phenolic compounds by ionic liquid. ACS Paragon Plus Environment

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

Page 22 of 41

AIChE. J. 2013, 59 (59), 1657-1667. (19) Ji, Y. A.; Hou, Y. C.; Yao, C. F.; Wu, W. Z. Highly efficient separation of phenolic compounds from oil mixtures by imidazolium-based dicationic ionic liquids via forming deep eutectic solvents. Energy Fuels. 2017, 31 (9), 10274-COVER3. (20) Alonso, L.; Arce, A.; Francisco, M.; Soto, A. Extraction ability of nitrogen-containing compounds involved in the desulfurization of fuels by using ionic liquids. J. Chem. Eng. Data. 2010, 55, 3262-3267. (21) Kedra-Krolik, K.; Fabrice, M.; Jaubert, J. Extraction of thiophene or pyridine from n-heptane using ionic liquids. Gasoline and diesel desulfurization. Ind. Eng. Chem. Res. 2011, 50 (4), 2296-2306. (22) Arce, A.; Earle, M. J.; Rodriguez, H.; Seddon, K. R. Separation of aromatic hydrocarbons from alkanes using the ionic liquid 1-ethyl-3-methylimidazolium bis{(trifluoromethyl) sulfonyl}amide. Green Chem. 2007, 9 (1), 70-74. (23) Hou, Y. C.; Ren, Y. H.; Peng, W.; Ren, S. H.; Wu, W. Z. Separation of phenols from oil using imidazolium-based ionic liquids. Ind. Eng. Chem. Res. 2013, 52 (50), 18071-18075. (24) Marcos, L.; Noemí, D.-M.; Pablo, N.; Roberto, A.; Cristian, M.; José, P.; Julian, G.; Francisco, R. Novel process to reduce benzene, thiophene, and pyrrole in gasoline based on [4bmpy][TCM] ionic liquid. Energy Fuels. 2018, 32, 5650-5658. (25) Zhang, F.; Li, Y.; Zhang, L. L.; Sun, W.; Ren, Z. Q. Selective separation of aromatics from paraffins and cycloalkanes using morpholinium-based ionic liquid. J. Chem. Eng. Data. 2015, 60 (6), 1634-1641. (26) Gao, J.; Ma, Y. X.; Zhang, L. Z.; Liu, W.; Xu, D. M.; Xu, X. C.; Wang, Y. L. Measurement and correlation of phase equilibria for ternary systems of water + (ethanol / 1-propanol) + ACS Paragon Plus Environment

Page 23 of 41 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

1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide at 298.15 K. Fluid Phase Equilibr. 2016, 427, 340-344. (27) Zhang, L. Z.; Xu, D. M.; Gao, J.; Zhang, M.; Xia, Z. M.; Ma, Y. X.; Zhou, S. X. Separation of the mixture pyridine + methylbenzene via several acidic ionic liquids: phase equilibrium measurement and correlation. Fluid Phase Equilibr. 2017, 440, 103-110. (28) Wang, P.; Xu, D. M.; Yan, P. S.; Gao, J.; Zhang, L. Z.; Wang, Y. L. Separation of azeotrope (ethanol and ethyl methyl carbonate) by different imidazolium-based ionic liquids: ionic liquids interaction analysis and phase equilibrium measurements. J. Mol. Liq. 2018, 261, 89-95. (29) Anugwom, I.; Mäki-Arvela, P.; Salmi, T.; Mikkola, J. P. Ionic liquid assisted extraction of nitrogen and sulphur-containing air pollutants from model oil and regeneration of the spent ionic liquid. J. Environ. Prot. 2011, 2 (6), 796-802. (30) Kubiczek, A.; Kaminski, W. Liquid-liquid extraction in systems containing butanol and ionic liquids-a review. Chem. Process Eng.-Inz. 2017, 38 (1), 97-110. (31) Kumar, A.; Thakur, A.; Panesar, P. S. Lactic acid extraction using environmentally benign green emulsion ionic liquid membrane. J. Clean. Prod. 2018, 181, 574-583. (32) Efimova, A.; Varga, J.; Matuschek, G.; Saraji-Bozorgzad, M. R.; Denner, T.; Zimmermann, R.; Schmidt, P. Thermal resilience of imidazolium based ionic liquids – studies on short- and long-term thermal stability and decomposition mechanism of 1-alkyl-3-methylimidazolium halides by thermal analysis and single-photon ionization time-of-flight mass spectrometry. J. Phys. Chem. B. 2018, In Press. DOI: 10.1021/acs.jpcb.8b06416. (33) Zhou, J. X.; Mao, J. B.; Zhang, S. G. Ab initio calculations of the interaction between thiophene and ionic liquids. Fuel Process. Technol. 2008, 89 (12), 1456-1460. ACS Paragon Plus Environment

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

Page 24 of 41

(34) Asumana, C.; Yu, G. R.; Guan, Y. W.; Yang, S. D.; Zhou, S. Z.; Chen, X. C. Extractive denitrogenation of fuel oils with dicyanamide-based ionic liquids. Green Chem. 2011, 13 (11), 3300-3305. (35) Su, X. L.; Song, J.; Yang, J. Y.; Xu, X. R. Extractive denitrification of coal tar diesel fraction using phosphate-based alkylimidazolium ionic liquids. Prog. Chem. 2016, 35, 1081-1086. (36) Feng, J. F.; Yuan, J.; Yang, M.; Wei, Y.; Chen, X. X. Removing basic nitrogen compounds from coker diesel with acid ionic liquid. J. Wuhan Inst. Technol. 2011, 33, 17-21. (37) Gao, P.; Cao, Z. B.; Zhao, D. Z.; Li, D. D.; Zhang, S. Y. Extraction of basic nitrides from FCC diesel using ionic liquids at room temperature. Petrol. Sci. Technol. 2005, 23 (9-10), 1023-1031. (38) Xie, L. L.; Favre-Reguillon, A.; Pellet-Rostaing, S.; Wang, X. X.; Fu, X. Z.; Estager, J. Selective extraction and identification of neutral nitrogen compounds contained in straight-run diesel feed using chloride based ionic liquid. Ind. Eng. Chem. Res. 2008, 47 (22), 8801-8807. (39) Zhang, L. Z.; Xu, D. M.; Gao, J.; Zhou, S. X.; Zhao, L. W.; Zhang, Z. S. Extraction and mechanism for the separation of neutral N-compounds from coal tar by ionic liquids. Fuel. 2017, 194, 27-35. (40) Wang, H.; Xie, C. X.; Yu S. T.; Liu, F. S. Removal of non-basic nitrogen in model oil with functionalized acidic ionic liquid. J. Fuel Chem. Technol. 2014, 42 (1), 55-60. (41) Huh, E. S.; Zazybin, A.; Palgunadi, J.; Ahn, S.; Hong, J.; Kim, H. S.; Cheong, M.; Ahn, B. S. Zn-containing ionic liquids for the extractive denitrogenation of a model oil: a mechanistic consideration. Energy Fuels. 2009, 23, 3032-3038. (42) Gabric, B.; Sander, A.; Bubalo, M. C.; Macut, D. Extraction of S- and N-compounds from the mixture of hydrocarbons by ionic liquids as selective solvents. Sci. World J. 2013, 2, 1-11. ACS Paragon Plus Environment

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(43) Krolikowska, M.; Karpinska, M. Extraction of aromatic nitrogen compounds from heptane using quinolinium and isoquinolinium based ionic liquids. Fluid Phase Equilibr. 2015, 400, 1-7. (44) Vilas, M.; González, E. J.; Tojo, E. Extractive denitrogenation of model oils with tetraalkyl substituted pyridinium based ionic liquids. Fluid Phase Equilibr. 2015, 396, 66-73. (45) Holbrey, J. D.; Reichert, W. M.; Nieuwenhuyzen, M.; Sheppard, O.; Hardacre, C.; Rogers, R. D. Liquid clathrate formation in ionic liquid–aromatic mixtures. Chem. Commun. 2003, 4, 476-477. (46) Hansmeier, A. R.; Meindersma, G. W.; de Haan, A. B. Desulfurization and denitrogenation of gasoline and diesel fuels by means of ionic liquids. Green Chem. 2011, 13 (7), 1907-1913. (47) Zhang, S. G.; Zhang, Z. C. Novel properties of ionic liquids in selective sulfur removal from fuels at room temperature. Green Chem. 2002, 4 (4), 376-379. (48) Orio, M.; Pantazis, D. A.; Neese, F. Density functional theory. Photosynth. Res. 2009, 102, 443-453. (49)

Wang,

Y.;

Li,

H.

R.;

Han,

S.

J.

Structure

and

conformation

properties

of

1-alkyl-3-methylimidazolium halide ionic liquids: A density-functional theory study. J. Chem. Phys. 2005, 123 (17), 6609. (50) Housaindokht, M. R.; Hosseini, H. E.; Googheri, M. S. S.; Monhemi, H.; Najafabadi, R. I.; Ashraf, N. Hydrogen bonding investigation in 1-ethyl-3-methylimidazolium based ionic liquids from density functional theory and atoms-in-molecules methods. J. Mol. Liq. 2013, 177 (8), 94-101. (51) Liu, J. B.; Chambreau, S. D.; Vaghjiani, G. L. Dynamics simulations and statistical modeling of thermal

decomposition

of

1-ethyl-3-methylimidazolium

dicyanamide

1-ethyl-2,3-dimethylimidazolium dicyanamide. J. Phys. Chem. A. 2014, 118 (47), 11133-11144.


and

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MO TE with an IL

U1

L1 BE with CCl4

analysis with GC/MS

U2

L2

BE with H2O and filtration

FC

filtrate evaporation

analyses with 1 H NMR and FTIRS

IL

reuse for TE of MO

H2O reuse for BE of U2

Figure 1. Procedure for carbazole extraction from MO and sample analyses.


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AO TE with CCl4

E1

R1 TE with EA

E2

analysis with GC/MS

R2

eluted with EA/hexane

Fc

retentate

TE with an IL

E3 Figure 2. Procedure for carbazole separation from AO and sample analysis.


Energy & Fuels

H N

N

100

Yield (%)

80 60 40 20 0 100 80 Purity (%)

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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60 40 20 0

ILa

ILb

ILc

ILd

IBIL Figure 3. Yields and purities of the 4 compounds isolated with different IBILs. ACS Paragon Plus Environment

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82 80

Yield (%)

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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78 76 74 72 64

68

72 76 Purity (%)

80

Figure 4. Yield vis purity of carbazole enriched with different IBILs.


84

100

82

96

82

96

80

92

80

92

78

88

78

88

84

76 30 min, IL /MO mass ratio = 1:4, MOC 25 a

84

80

mg mL-1 74 290 300

80

MOC 25 mg mL-1 74 0

20

40 60 Time (min)

80

100

310 320 Temperature (K)

330

340

100

100

92

96

97

96

84

92

94

92

76

88

91

88

68

Yield (%)

100

Purity (%)

100

84

88

80

85 10

-1

30 min, 303.15 K, MOC 25 mg mL 60 1:8

1:4 1:2 1:1 ILa/MO mass ratio

2:1

Purity (%)

303.15 K, ILa/MO mass ratio = 1:4,

Yield (%)

84

Purity (%)

100

Purity (%)

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84

76

Yield (%)

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

Yield (%)

Energy & Fuels

84

30 min, 303.15 K, ILa/MO mass ratio = 1:1

80 19

28 37 MOC (mg mL-1)

46

55

Figure 5. Effects of time, temperature, ILa/MO mass ratio, and MOC on the yield and purity of carbazole separated.


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100 80

MO

60 N

40

N H

20 Relative 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

Energy & Fuels

0 100 80

U1

60 40

N

20 0 100 80

FC N H

60 40 20 0 16

17

18

19

20

21

22

23 24 25 26 27 Retention time (min)

28

Figure 6. Ion chromatograms of MO, U1, and FC. ACS Paragon Plus Environment

29

30

31

32

33

34

Energy & Fuels

E1

E2

Fc

E3

TRC (area %)

80 60 40 20 0

AAs

acridines

ATs

BNFs

C & BCs

DATs

DBFs

DMCs

TRC (area %)

5 4 3 2 1 0

DMNs

DMPs

EAs

ECs

F & BFs

HAs

IQs

MAs

MBPs

MCs

MFI & MPsII

MFsII

MNs

MPsI

NNs

NSCAs

OCs

phenanthridines

PNs

PPs

TMNs

TRC (area %)

20 15 10 5 0 60

TRC (area %)

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

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45 30 15 0

Group component

Figure 7. Distribution of group components in E1-E3 and Fc according to the analysis with GC/MS. ACS Paragon Plus Environment

623 584 525 432

935 843 754

2232 2194 2134

1616 1569 1496 1462 1390 1310 1240 1170

ILa

2958 2872

3149 3146

3482 3414

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

Energy & Fuels

Absorbance

Page 33 of 41

ILa-carbazole

carbazole

4000

3600

3200

2800

2400 2000 Wavenumber (cm-1)

1600

Figure 8. FTIR spectra of ILa, ILa-carbazole, and carbazole.


1200

800

400

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Figure 9. The structural formula and atomic number of ILa.


Page 34 of 41

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0.2028 nm 0.2122 nm

ILa...carbazole

ILb...carbazole

Figure 10. Bond lengths between ILa and carbazole and between ILb and carbazole.


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-7.075 e-2

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7.075 e-2

Figure 11. Electron cloud density distributions of ILa and carbazole.


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100

80

80

60

60

40

40

20

20

0

0

1 2 Recycle times

3

Figure 12. Recycling ratio of ILa and carbazole yield with fresh and recycled ILa.


0

Carbazole yield (mol%)

100

Recycling ratio of ILa (%)

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

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

fresh

a h

N

b

N + N c N g N

Page 38 of 41

h f

d e

f

c g

d

DMSO-d6

ab

e

h

first recycled

c g

10

9

f DMSO-d6

d

e

ab

8

7

6 5 4 Chemical shift (ppm)

3

Figure 13. 1H NMR spectra of fresh and recycled ILa.


2

1

0

Page 39 of 41 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

Table 1. Data for the Lengths of Some Hydrogen Bonds. Bond length (nm) Hydrogen bond ILa N26-carbazole N29-carbazole N30-carbazole N29-H17

0.239 0.240

0.216

0.212

N30-H11

0.238 0.239

0.242

0.256

N30-H16

0.217 0.219

0.228

0.237

0.201

0.203

0.206

ILa-carbazole


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

Table 2. ΔH between ILa and Carbazole Calculated. Hcorr H(T) ele ILa (Hartree) -663.491154 0.268657 -663.222497 Carbazole (Hartree) -517.204988 0.187169 -517.017819 ILa-carbazole (Hartree) -1180.711391 0.458106 -1180.253285 ΔH (kJ mol-1) -40.034937 5.986140 -34.048797


Page 40 of 41

Page 41 of 41 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

Table 3. ΔH between ILb and Carbazole Calculated. Hcorr H(T) ele ILb (Hartree) -883.277424 0.241713 -883.035711 Carbazole (Hartree) -517.204988 0.187169 -517.017819 ILb-carbazole (Hartree) -1400.495194 0.431064 -1400.064130 ΔH (kJ mol-1) -33.560454 5.728841 -27.831613


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