Desulfurization of Fuel Oil: Conductor-like Screening

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Desulfurization of Fuel Oil: COSMO-RS Study on Capacity of Ionic Liquids for Thiophene and Dibenzothiophene shurong gao, Xiaochun Chen, Rashid Abro, Ahmed A. Abdeltawab, Salem S. Al-Deyab, and Guangren Yu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b01385 • Publication Date (Web): 08 Sep 2015 Downloaded from http://pubs.acs.org on September 8, 2015

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Industrial & Engineering Chemistry Research

Desulfurization of Fuel Oil: COSMO-RS Study on Capacity of Ionic Liquids for Thiophene and Dibenzothiophene Shurong Gaoa, Xiaochun Chena, Rashid Abroa, Ahmed A. Abdeltawabb, Salem S. Al-Deyabb, Guangren Yua,* a

Beijing Key Laboratory of Membrane Science and Technology & College of Chemical Engineering, Beijing University of

Chemical Technology, Beijing 100029, P. R. China b

Petrochemicals Research Chair, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

* Corresponding author, Tel./Fax: +86-10-6443-3570, E-mail: [email protected]

Abstract: To screen and use ionic liquids (ILs) as environmental-friendly extractive solvents in removing aromatic sulfur compounds (S-compounds) from fuel oils, the knowledge of their capacity for S-compounds (or solubility of S-compounds in ILs) is very important. In this work, the capacities of 1860 potential ILs (30 anions, 62 cations) for two representative S-compounds of thiophene (TS) and dibenzothiophene (DBT) are calculated using conductor-like screening model for real solvents (COSMO-RS). The influences of cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length and functional group on the capacity are extensively discussed and are understood from a view of micro-level with σ-profile, σ-moments and COSMO-RS energies. It is observed that the capacity is very dependent on cation and anion structure characteristic and is in very wide range (e.g., 10-3~101 for TS, 10-3~102 for DBT); the van der Waals (vdW) and hydrogen-bonding (HB) energies have significant effects on the capacity. Increasing the non-polarity and vdW energies of cation or alkyl chain on anion, or the polarity and HB energies of anion can favor the capacity. This work is valuable to rationally select or design the ILs for desulfurization of fuel oils. Keywords: Ionic liquids, capacity, COSMO-RS, thiophene, dibenzothiophene.

Introduction Sulfur compounds in fuel oils give rise to the emissions of SOX and particulates during combustion of fuel oils1-3. To reduce the pollution caused by vehicle exhausts, many countries are setting more and more stringent legislation to limit S-content in fuel oils2,4-7. Requirement for producing S-ultra-low or S-free fuel oils is bringing many challenges to traditional hydrodesulfurization technology (HDS, which is widely employed in

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industry)8,9; because HDS is not effective to remove some heterocyclic S-compounds such as thiophene (TS), dibenzothiophene (DBT) and their derivatives due to the steric hindrance adsorption on catalyst surface; also HDS requires very harsh conditions such as high temperature, high pressure and expensive catalysts, and this results into high cost. Alternative methods such as extractive desulfurization (EDS), oxidative desulfurization (ODS), adsorptive desulfurization and biodesulfurization were studied, among which no one, however, is used in large scale in industry for their respective problems. Recently, a new class of desulfurization methods are being studied, i.e., EDS and ODS with ILs as solvents insteading of traditional molecule-type solvents. For EDS, S-compounds are extracted from oil to ILs and removed; for ODS, S-compounds are extracted into ILs, oxidized to higher polar sulfones, and removed. Owing to some desirable properties of ILs10-12 such as negligible vapour pressure, high thermal/chemical stabilities, tunable dissolving or extracting capabilities for inorganic or organic compounds and recyclability, such new methods avoid some problems caused by volatile organic solvents in traditional EDS and ODS such as solvent volatile loss and contamination/pollution, and make regeneration and recycle of solvent easier. Those heterocyclic S-compounds immune to HDS can be effectively removed in such methods, e.g., S-content in diesel fuel composed of DBT and octane can be reduced from 1000 ppm to < 10 ppm after only one stage of ODS (1-acetic acid-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, 1 ml; oil, 1 g; 30w% H2O2, 0.1 ml; 50˚C)13. Compared with the very huge IL pool (the number of reported ILs is estimated to be ~2000 while the number of potential ILs is ~1018), the number of ILs that were studied experimentally in desulfurization is very limited as listed in Tables S1~S214-38. There is still large room to further design and select the ILs with higher desulfurization efficiency and better physiochemical properties. Further, the heterocyclic S-compounds such as TS and DBT are extracted into IL phase first and then removed through physical or chemical oxidation in such new methods; therefore, one ideal IL has to have a good solubility or capacity for the heterocyclic Scompounds. To screen those ILs with high capacity for the S-compounds, experimental test one by one alone is too time-consuming, costly and impractical while computer simulation such as direct prediction or calculation of the capacity using some thermodynamics theories (e.g., Conductor-like Screening Model for Real Solvents, COSMO-RS) is an effective way.

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COSMO-RS39-43 is a well-established thermodynamics model that only requires information on the atoms of the compounds with no need for experimental data. This model has been used to calculate the thermodynamics properties and phase behaviors about ILs such as enthalpies of vaporization41,42, gas solubility44-46, infinite dilution activity coefficients of organic compounds47-49, liquid-liquid equilibria of hydrocarbons and ILs50-53 and capacity of ILs for hydrocarbons54,55. A few studies have been reported on employing COSMO-RS to predict the capacities of ILs for TS and DBT, e.g., Kumar et al.56 studied the capacity of 264 ILs for TS, Anantharaj et al.54 reported the capacity of 168 ILs for TS and DBT, Wilfred et al.57 investigated the ability of 21 ILs to extract DBT from n-dodecane, and Song et al.58 reported the capacity of 216 ILs for TS. As the full description of COSMO-RS equations are given elsewhere42,43,59, only the major features for understanding the prediction and analysis in the present work are emphasized here. In this work, the capacity of IL for S-compounds is calculated by ∞ ci ∞ = 1/ γ i,IL

where i is the key components and here is TS or DBT,

(1) ci∞

is the solvent capacity at infinite dilution of

∞

solubility screening (solute in IL), and γ i , IL is the activity coefficient of component i at infinite dilution in IL. It should be mentioned that 1) the capacity is equivalent to solubility, which is only valid for small concentrations of the solute, i.e. if the solubility itself is small; 2) in the COSMO-RS calculation, ILs are treated as electro-neutral mixtures of separated cations and anions. In this work, we study the capacity of ILs for S-compounds. 1) A IL pool composed of 1860 possible ILs is constructed, involving 30 anions and 62 cations (the full names and short names with chemical structure are provided in Tables S3~S4, respectively). 2) The capacities of these ILs for two typical S-compounds of TS and DBT are calculated employing COSMO-RS, and the results are given in Tables S5~S6, respectively. 3) Following the COSMO-RS results, the effects of ILs structure on the capacity are analyzed, including Scompound species, cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length, and functional group. 4) σ-profile, σ-moments and COSMO-RS energies are employed to understand the effects of ILs structure on the capacity. 5) The nature of the effects of ILs structure on the capacity is uncovered. These ILs with high capacity screened out are potential candidates to be used in desulfurization of

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fuel oils, and understanding of the effects of ILs structure on the capacity uncovered in this work provides the theoretical basis for the design and selection of ILs used in the desulfurization of fuel oils in future.

Results and Discussion Validation of COSMO-RS Prediction There are not experimental data of the capacity of ILs for TS and DBT available. We compared the capacity of some ILs for TS and DBT calculated from COSMO-RS with the experimental desulfurization efficiencies in EDS that were reported in the literatures. The comparison results are shown in Figure 115,16,17,19,21,23,60 and Figure S115,18,19,23-27,61,62. As shown in Figures 1 and S1, the desulfurization efficiencies rigidly increase with the capacity of ILs for TS and DBT, which is consistent with the expected fact that higher capacity brings better desulfurization efficiency. Capacity of ILs for TS and DBT Capacities of ILs for TS and DBT from COSMO-RS calculations are shown in Figure S2. As indicated in Figure S2, the capacity mostly depends on the nature of ILs, i.e., cation family, anion family, or the pairing of cation and anion, e.g., the capacities of [BF4]‾-based ILs for TS are 0~2 and that for DBT are 0~0.5; while [Cl]‾based ILs for TS are 0~62 and that for DBT are 0~820. The influence of anion is stronger than that of cation. Next, we will discuss the effects of ILs structure on capacity in detail, including cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length, and functional group. Understanding of the Effect of Structure on the Capacity Cation family. Effects of cation family are shown in Figure 2. Cation family has a remarkable effect on the capacity, e.g., [bmpip]+, [bmpyr]+, [bmpy]+ and [bmim]+ have the same alkyl characteristics with different cation cores while have very different capacity. The capacities of ILs for TS and DBT both follow this order: [SC2(C1)4iU]+ > [BTPP] + > [bmpip]+ > [bmpyr]+ > [bmpy]+ > [bmim]+ > [Ch]+ > [G]+. The effect of cation family on capacity is explained based on the results in Figures 3~4 and Tables 1~3. The σ-profiles of other cations are shown in Figures S3~S4. As shown in Figure 3, the peaks for [SC2(C1)4iU]+, [BTPP]+, [bmpip]+, [bmpyr]+, [bmpy]+ and [bmim]+ are 4


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located in the non-polar region43,54,58,63 of σ=-0.0082 e/Å2~σ=0.0082 e/Å2, and the peak areas follow [SC2(C1)4iU]+ > [BTPP] + > [bmpip]+ > [bmpyr]+ > [bmpy]+ > [bmim]+ ; while the peaks for [Ch]+ and [G]+ are located at σ =-0.018 e/Å2 and σ = -0.017 e/Å2 in polar areas, respectively, with very similar polarity. Thus, the non-polarity for these cations follow [SC2(C1)4iU]+ > [BTPP] + > [bmpip]+ > [bmpyr]+ > [bmpy]+ > [bmim]+ > [Ch]+ ≈ [G]+, which is roughly in the same order to the capacity, and implies that more non-polarity for cations results in higher capacity. In addition, the polarity characteristics for these cations in Figure 3 can be understood by σ-moments (there are two important σ-moments related to hydrogen bonds, namely HB_acc3 and HB_don3, representing the capability of a hydrogen bond acceptor and a hydrogen bond donor, respectively)43,63 in Table 1 and the multiple TS/DBT−IL interaction energies63 from COSMO-RS computation in Tables 2~3, where the more polar cations have the larger HB_don3 values and higher HB energies. Tables 2~3 also indicate more nonpolar cations have higher vdW and misfit energies and have higher affinity for TS/DBT, thus have higher capacity for TS/DBT. The clearer presentations of the variations of HB_don3, HB energy, vdW energy and misfit energy along with cations are shown in Figure 4; the results discussed above are demonstrated in Figure 4, though there are rather limited exceptions. Cation alkyl chain length. The effects of alkyl chain length of imidazolium cation ([Cnmim]+, with n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 and 16) are illustrated in Figure 5. The capacities for both TS and DBT follow the same trend: [C1mim]+ < [C2mim]+ < [C3mim]+ < [C4mim]+ < [C5mim]+ < [C6mim]+ < [C7mim]+ < [C8mim]+ < [C9mim]+ < [C10mim]+ < [C12mim]+ < [C16mim]+, i.e., the cation alkyl chain length is longer, the capacity is larger. The effects of cation alkyl chain length are similar to that of cation family, and can be explained in similar way. As shown in Figure S5, the peaks of all [Cnmim]+ are located in non-polar area. The alkyl chain of cation is longer, the peak area is larger, the non-polarity and vdW energies are stronger, thus results to stronger affinity for TS/DBT and the higher capacity, which also can be understood by the energy characteristics in Tables 2~3, the values of HB_don3 in Table 1, and the relationship between HB_don3 and COSMO-RS energies in Figure S6. Similar conclusions can be reached for pyridinium cation ([Cnpy]+, with n = 1, 2, 4, 6, 8), pyrrolidinium cation ([Cnmpyr]+, with n = 1, 2, 4, 5, 6, 8), and ammonium cation ([Nn111]+, with n = 1, 2, 4, 6, 7, 8, 14) as shown in Figures S7~S15 and Tables 1~3.

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Cation symmetry. Alkylimidazolium cation of [Cnim]+ and [CnCnim]+ (n=1 or n=2) are selected to investigate the effect of cation symmetry. The capacity for both TS and DBT with the [C1im]+ and [C1C1im]+ based ILs are shown in Figure 6. The capacity of symmetric [C1C1im]+ is much higher than that of asymmetric [C1im]+, which can be understood by the more non-polarity59 of [C1C1im]+ than [C1im]+ as indicated by the peak positions in polar area in Figure S16 ([C1C1im]+: σ = -0.0075 e/Å2; [C1im]+: σ = -0.02 e/Å2). The more non-polarity and the stronger vdW energies result into the higher capacity as shown in Figure S17 and Tables 2~3. Similar results can be observed for [C2mim]+ and [C2C2im]+, [C2C3im]+ and [C2C2im]+, [(EOH)2N]+ and [(EOH)Me2N]+as shown in Figures S18~S23 and Tables 1~3. To summarize the discussion of cation effect above, the cation with more non-polarity and stronger vdW energies has higher affinity for TS/DBT and the resultant higher capacity. Anion nature. The capacities for TS/DBT of the ILs with different anions are shown in Figure 7. Figure 7 shows that the capacities for TS and DBT of the ILs both follow this order: [Cl]- > [Br]- > [Ac]- > [MeSO3]- > [DMP]- > [SCN]- > [BF4]- > [BMB]-. Contrary to cation, the anions with higher capacity basically have higher polarity, and this point can be observed in Figure S24, where the peaks of all the anions are located in the positive polar range of 0.01 < σ(e/Å2) < 0.02 with specific positions (σ(e/Å2)) of [Cl]- (0.020), [Br]- (0.018), [Ac]- (0.02), [MeSO3]- (0.018), [DMP]- (0.017), [SCN]- (0.013), [BF4]- (0.011) and [BMB]- (0.012). The polarities of these anions are also understood by the COSMO Descriptor HB_acc3 in Table 4 and COSMO-RS energies in Tables 5~6, i.e, more polarity for anions is consistent with higher values of HB_acc3 roughly and stronger HB energies in the mixture, thus leading to stronger affinity for TS/DBT and finally cause the higher capacity. The results discussed above are demonstrated in Figure S25. The σ-profiles of other anions are shown in Figures S26. Anion alkyl chain length. Three type of anions with different length of alkyl chain are selected to investigate the effect of anion alkyl chain length, i.e., [RSO4]- where R = methyl (Me), ethyl (Et), butyl (Bu) and octyl (Oc), [ROEtSO4]- where R = Me and Et, [DRP]- where R =Me, Et and Bu, and the results are shown in Figures 8, S29, and S32, respectively. As shown in Figure 8, the capacity for TS/DBT follows the order [MeSO4]-＜[EtSO4]-＜ [BuSO4]-＜[OcSO4]-, i.e., the anion alkyl chain is longer, the capacity is higher. Therefore, the effect of anion alkyl chain length is the same to that of cation alkyl chain length, as also shown in Figures S27~S28 and Tables

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4~6, i.e., longer alkyl chain length, stronger van der Waals interaction, thus stronger affinity for TS/DBT and higher capacity. In Figure S27, it is worthy of noting interestingly that the peaks for all the anions are overlapped in polar region while are different in non-polar region. Similar conclusions can be reached for [ROEtSO4]- and [DRP]-, as shown in Figures S29~S34 and Tables 4~6. To summarize the discussion of anion effect above, the anion with higher polarity and stronger HB energies has higher affinity for TS/DBT and the resultant higher capacity; further, for the same anion, the alkyl chain is longer, the vdW energy is stronger, thus the affinity for TS and DBT is stronger, and the capacity is higher. Functional group. Sulfate anions are selected to investigate the effects of functional group on anion, and the capacity results are shown in Figure 9, which includes the groups of ether, hydroxyl and phenyl. Some observations can be concluded from Figure 9. (1) The addition of ether favors the capacity, e.g., the capacities: [MeOEtSO4]- > [EtSO4]-, [MDEGSO4]- > [EtOEtSO4]-, [EtOEtSO4]- > [EtSO4]-, [MeOEtSO4]- > [MeSO4]-, [MDEGSO4]- > [MeOEtSO4]-, [EtOEtSO4]- > [MeSO4]-. This can be understood as follows. The addition of ether enlarges their non-polar region, the vdW energies and the affinity for TS/DBT, as shown in Figure S35 and Tables 5~6. This effect of ether on the side chain of sulfate anions is the same to that of anion alkyl chain length discussed above. (2) The additions of hydroxyl and phenyl decrease the capacity, e.g., the capacities: [TOS]- < [MeSO3]-, [HSO4]- < [MeSO3]-. The additions of hydroxyl and phenyl significantly reduce the polarities; and reduce the HB energies, which is consistent with the COSMO Descriptor HB_acc3 in Table 4. As a result, the affinity for TS/DBT is weakened and the capacities are lowered. The results of the effects of functional group on cation are shown in Figure 9, which includes the groups of oxygen inclusion and hydroxyl. The additions of oxygen inclusion and hydroxyl decrease the capacity, e.g., the capacities: [C2mpyr]+ < [EOEMPyr]+, [(NEMM)MOE]+ < [EtMe2PrN]+, [Ch] +< [Me3EtN]+, [MOPMPip]+ < [BMPip]+, [EOEMPyr]+ < [C2mpyr]+. It is ascribed to this fact that the additions of oxygen inclusion and hydroxyl decrease their non-polar region, the vdW energies and the affinity for TS/DBT, as shown in Figure S36 and Tables 5~6. To summarize the discussion of functional group, the functional group that increases the non-polarity and vdW energies for cation and anion side chain, or increases the polarity and HB energies for anion, will enhance the

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capacity for TS/DBT. Revisit Experimental Results with COSMO Understanding The experimental desulfurization efficiency in Figure 1 is revisited with the above COSMO understandings. As shown in Figure 1, the desulfurization efficiency follows the order, e.g., (1) [C2mim][BF4] < [C4mim][BF4] < [C6mim][BF4]16, [C1mim][MeSO4] < [C2mim][MeSO4] < [C4mim][MeSO4]60, [C2mim][EtSO4] < [C2eim][EtSO4] < [C4epy][EtSO4]60, [C2mpy][BF4] < [C6mpy][BF4] < [C8mpy][BF4]21, [C4py][BF4] < [C8py][BF4]15, [C4mim][BF4] < [C8mim][BF4]15, cation alkyl chain↑, non-polarity↑, vdW energies↑, capacity↑, desulfurization efficiency↑; (2) [C4mim][BF4] < [C4mim][MeSO4] < [C4mim][SCN]16, [C2mim][Tf2N] < [C4mim][Ac]21, anion polarity↑, HB energies↑, capacity↑, desulfurization efficiency↑; (3) [C2mim][MeSO4] < [C2mim][EtSO4]60, anion alkyl chain↑, non-polarity↑, vdW energies↑, capacity↑, desulfurization efficiency↑. It should be pointed that there is not experimental data of the capacity of ILs for TS and DBT available, and we compared the capacity of some ILs for TS and DBT calculated from COSMO-RS with the experimental desulfurization efficiencies reported in the literatures, which is consistent with the expected fact that higher capacity brings better desulfurization efficiency.

Conclusion Due to the ineffectiveness of traditional HDS in removing some aromatic S-compounds such as TS, DBT and their derivatives, using ILs as novel extractive solvents to remove these S-compounds from fuel oils are being intensively studied; therefore, the knowledge of ILs capacity for S-compounds is very important. In this work, the capacities of 1860 potential ILs for TS and DBT were calculated with COSMO-RS. Following the calculated results, the influences of cation family, cation alkyl chain length, cation symmetry, anion nature, anion alkyl chain length and functional group on capacity were discussed and understood from a view of micro-level with σ-profile, σ-moments and COSMO-RS energies. Some interesting and valuable conclusions are as follows: (1) the capacity is very dependent on cation and anion species, with a very wide range (e.g., 103

~101 for TS, 10-3~102 for DBT); (2) HB and vdW energies between TS/DBT and ILs dominantly contribute to

the capacity; (3) the cation that has more non-polarity, longer alkyl chain and more symmetric in structure, will have higher capacity for TS/DBT with stronger vdW energies and affinity; while the anion that has higher

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polarity will have the higher capacity with stronger HB energies and affinity; in addition, the longer alkyl chain on anion will enhance vdW energies and capacity; (4) the functional groups have to be tailored carefully, and such groups that can increase the non-polarity and vdW energies of cation or alkyl chain on anion, or the polarity and HB energies of anion, will favor the capacity. This work is expected to contribute to the rational selection or design of ILs for desulfurization of fuel oils.

Acknowledgment This work was financially supported by National Natural Science Foundation of China (21176021, 21276020) and Fundamental Research Funds for the Central Universities (YS1401). We extend our appreciation to the Deanship of Scientific Research at King Saud University for funding the work, through Research Group Project No. RG-1436-026.

Supporting Information Available This information is available free of charge via the Internet at http://pubs.acs.org/.

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40. Diedenhofen, M.; Klamt, A. COSMO–RS as a Tool for Property Prediction of IL Mixtures – A Review. Fluid Phase Equilib. 2010, 294, 8–31. 41. Klamt, A.; Eckert, F.; Arlt, W. COSMO–RS: An Alternative to Simulation for Calculating Thermodynamic Properties of Liquid Mixtures. Annu. Rev. Chem. Biomol. 2010, 1, 101–22. 42. Klamt, A. COSMO–RS from Quantum Chemistry to Fluid Phase Thermodynamics and Drug Design. Amsterdam: Elsevier, 2005. 43. Eckert, F.; Klamt, A. COSMOtherm, version C3.0; COSMOlogic GmbH & Co. KG: Leverkusen, Germany, 2013. 44. Klamt, A. Prediction of the Mutual Solubilities of Hydrocarbons and Water with COSMO–RS. Fluid Phase Equilibr. 2003, 206, 223–235. 45. Lei, Z. G.; Arlt, W.; Wasserscheid, P. Separation of 1–Hexene and N–Hexane with Ionic Liquids. Fluid Phase Equilibr. 2006, 241, 290–299. 46. Zhang, X. C.; Liu, Z. P.; Wang, W. C. Screening of Ionic Liquids to Capture CO2 by COSMO–RS and Experiments. AIChE J. 2008, 54, 2717–2728. 47. Banerjee, T.; Khanna, A. Infinite Dilution Activity Coefficients for Trihexyltetradecyl Phosphonium Ionic Liquids: Measurements and COSMO–RS Prediction. J. Chem. Eng. Data 2006, 51, 2170–2177. 48. Klamt, A.; Eckert, F.; Diedenhofen, M. Prediction or Partition Coefficients and Activity Coefficients of Two Branched Compounds Using COSMOtherm. Fluid Phase Equilib. 2009, 285, 15–18. 49. Diedenhofen, M.; Eckert, F.; Klamt, A. Prediction of Infinite Dilution Activity Coefficients of Organic Compounds in Ionic Liquids Using COSMO–RS. J. Chem. Eng. Data 2003, 48, 475–479. 50. Banerjee, T.; Singh, M. K.; Khanna, A. Prediction of Binary VLE For imidazolium Based Ionic Liquid Systems Using COSMO–RS. Ind. Eng. Chem. Res. 2006, 45, 3207–3219. 51. Lei, Z. G.; Chen, B. H.; Li, C. Y. COSMO–RS Modeling on the Extraction of Stimulant Drugs from Urine Sample by the Double Actions of Supercritical Carbon Dioxide and Ionic Liquid. Chem. Eng. Sci. 2007, 62, 3940–3950. 52. Ferreira, A. R.; Freire, M. G.; Ribeiro, J. C.; Lopes, F. M.; Crespo, J. G.; Coutinho, J. A. P. Overview of the Liquid–Liquid Equilibria of Ternary Systems Composed of Ionic Liquid and Aromatic and Aliphatic Hydrocarbons, and Their Modeling by COSMO–RS. Ind. Eng. Chem. Res. 2012, 51, 3483–3507. 53. Ferreira, A. R.; Freire, M. G.; Ribeiro; J. C.; Lopes, F. M.; Crespo, J. G.; Coutinho, J. A. P. An Overview of the Liquid–Liquid Equilibria of (ionic liquid1hydrocarbon) Binary Systems and Their Modeling by the Conductor–Like Screening Model for Real Solvents. Ind. Eng. Chem. Res. 2011, 50, 5279–5294. 54. Anantharaj, R.; Banerjee, T. COSMO–RS Based Predictions for the Desulphurization of Diesel Oil Using Ionic Liquids: Effect of Cation and Anion Combination. Fuel Process. Technol. 2011, 92, 39–52 55. Lei, Z. G.; Dai, C. N.; Zhu, J. Q.; Chen, B. H. Extractive Distillation with Ionic Liquids: A Review. AIChE J. 2014, 60, 3312–3329. 56. Kumar, A.; Banerjee, T. Thiophene Separation with Ionic Liquids for Desulphurization: A Quantum 12


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Figure 1. The capacity of ILs for DBT (☆ ☆) predicted by COSMO-RS and from experimental desulfurization efficiencies (, Ref.15; ╋ , Ref.16; ⃞, Ref17; △ , Ref.19; ▽ , Ref.21; ○, Ref.23; ◐ Ref.60.)

14


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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


+ + + + + + + ☆) [SC2(C1)4iU] ; (◇ ◇) [BTPP] ; (▽ ▽) [bmpip] ; (△ △) [bmpyr] ; (○ ○) [bmpy] ; (⃞ ⃞) [bmim] ; (╋ ╋) [Ch] ; Figure 2. The capacity of ILs for TS and DBT at 298.15 K. (☆

(⊲ ⊲) [G]+.

15



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Figure 3. σ-profiles of TS, DBT and eight studied cations.

16


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Figure 4. Relationships between the HB_don3 with the HB energy, vdW energy and misfit energy of eight studied cations.

17



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Page 18 of 31

) bismalonatoborate [BMB]- ; ( ) ethylsulfate [EtSO4]- ; ( ) Figure 5. The capacity of [Cnmin]+ based ILs for TS and DBT at 298.15K. ( methoxyethylsulfate [MeOEtSO4]-; ( ) toluene-4-sulfonate [TOS]-; ( ) hydrogensulfate [HSO4]-; ( ) diethylphosphate [DEP]-; ( ) dibutylphosphate [DBP]-;( ) dicyanamide [DCA]-; ( ) dicyano(nitroso)methanide [DCNM]-.

18


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Figure 6. The capacity of [C1im]+ and [C1C1im]+ based ILs for TS and DBT at 298.15K.

19



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Figure 7. The capacity of ILs for TS and DBT at 298.15 K.

20


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Figure 8. The capacity of [MeSO4]−, [EtSO4]−, [BuSO4]− and [OcSO4]− based ILs for TS and DBT at 298.15 K.

21



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╋) [MeSO4] ; (◇ ◇) [EtSO4] ; (◐ ◐) [MeOEtSO4] ; (△ △) [EtOEtSO4] ; (Ⅹ Ⅹ) [MDEGSO4] ; (⃞ ⃞) [TOS] ; (☆ ☆) Figure 9. The capacity of ILs for TS and DBT at 298.15 K. (╋

[MeSO3]-; (⊲ ⊲) [HSO4]-.

22


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Table 1. COSMO Descriptor HB_don3 for Typical Cations cation 3-methyl-imidazolium

HB_don3 1.991

cation 1-methyl-1-pentylpyrrolidinium

HB_don3 0.842

1-butyl-imidazolium

8.597

1-hexyl-1-methyl-pyrrolidinium

0.062

1,3-dimethyl-imidazolium

1.981

1-octyl-1-methyl-pyrrolidinium

0.061

1-ethyl-3-methyl-imidazolium

1.980

1-butyl-1-ethyl-pyrrolidinium

0.035

1-propyl-3-methyl-imidazolium 1-butyl-3-methyl-imidazolium

1.944 1.935

1,1-dipropyl-pyrrolidinium 1-(2-ethoxyethyl)-1-methylpyrrolidinium

6E-04 0.124

1-pentyl-3-methyl-imidazolium

1.937

bis(2-methoxyethyl)ammonium

7.154

1-hexyl-3-methyl-imidazolium

1.917

butyl-diethanolammonium

5.926

1-heptyl-3-methyl-imidazolium 1-octyl-3-methyl-imidazolium

1.945 1.947

di-ethyl-di-isopropylammonium diethanolammonium

0.024 12.790

1-methyl-3-nonylimidazolium

1.900

dimethylethanolammonium

7.270

1-decyl-3-methyl-imidazolium

1.929

dodecyl-dimethyl-3-sulfopropylammonium

6.817

1-dodecyl-3-methyl-imidazolium 1-hexadecyl-3-methyl-imidazolium

1.927 1.923

ethyl-dimethyl-2-methoxyethylammonium ethyl-dimethyl-propylammonium

0.246 0.133

1,3-diethylimidazolium

1.977

n-butyl-n-propyl-n,n-dimethylammonium

0.146

1-ethyl-3-propylimidazolium

1.978

triethylpentylammonium

0.007

1-butyl-3-ethylimidazolium

1.987

n-hexyl-n,n,n-triethylammonium

0.012

1-methyl-pyridinium

1.327

triethylheptylammonium

0.006

1-ethyl-pyridinium 1-butyl-pyridinium

1.246 1.204

tetra-methylammonium trimethylethylammonium

0.388 0.250

1-hexyl-pyridinium

1.202

butyltrimethylammonium

0.239

1-octyl-pyridinium

1.201

hexyltrimethylammonium

0.233

1-butyl-3-ethyl-pyridinium 1-ethyl-3-methylpyridiniumcosmo

1.005 0.931

heptyltrimethylammonium octyltrimethylammonium

0.245 0.225

1-butyl-3-methyl-pyridinium

1.010

tetradecyltrimethylammonium

0.226

1-hexyl-3-methyl-pyridinium

0.998

1-butyl-1-methylpiperidinium

0.058

3-methyl-1-octyl-pyridinium benzyl-triphenyl-phosphonium

1.003 0.829

1-(3-methoxypropyl)-1-methylpiperidinium guanidinium

0.122 23.820

1,1-dimethyl-pyrrolidinium

0.118

n,n,n,n-tetramethyl-n-ethylguanidinium

2.207

1-ethyl-1-methyl-pyrrolidinium

0.066

choline

1.251

1-butyl-1-methyl-pyrrolidinium

0.063

s-ethyl-n,n,n,n-tetramethylisothiouronium

0

23



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Table 2. COSMO-RS volume, misfit, hydrogen-bonding and van der Waals energies for the capacity of TS in the [DBP]-based ILs combinations at 298.15 K Ionic Liquid Cation

EMF (kcal/mol)

EHB (kcal/mol)

EVdW (kcal/mol)

3-methyl-imidazolium

6.520

-5.490

-7.321

1-butyl-imidazolium

7.160

-5.383

-9.345


7.854

-1.646

-7.475


8.201

-1.536

-8.453

1-propyl-3-methyl-imidazolium

8.456

-1.524

-9.852

1-butyl-3-methyl-imidazolium

8.881

-1.501

-10.568


9.012

-1.495

-10.865


9.286

-1.502

-12.027

1-heptyl-3-methyl-imidazolium

9.854

-1.513

-12.895

1-octyl-3-methyl-imidazolium

10.249

-1.517

-14.775


11.026

-1.526

-15.632


12.237

-1.523

-17.021

1-dodecyl-3-methyl-imidazolium

12.965

-1.512

-19.300

1-hexadecyl-3-methyl-imidazolium

13.027

-1.511

-23.197


7.965

-1.536

-9.621


8.892

-1.503

-10.586


9.126

-1.486

-11.029

1-methyl-pyridinium

7.957

-1.411

-7.895

1-ethyl-pyridinium

8.092

-1.395

-8.216

1-butyl-pyridinium

8.763

-1.355

-10.312

1-hexyl-pyridinium

9.237

-0.352

-11.897

1-octyl-pyridinium

10.690

-0.337

-11.996 -10.844

1-butyl-3-ethyl-pyridinium

9.365

-0.390

1-ethyl-3-methylpyridiniumcosmo

8.611

-1.114

-9.226


9.264

-1.081

-11.253


10.021

-0.303

-11.921

3-methyl-1-octyl-pyridinium

10.986

-0.201

-12.367

benzyl-triphenyl-phosphonium

12.502

-0.808

-19.158


8.563

-0.542

-8.021


8.976

-0.538

-8.602


9.624

-0.523

-10.684

1-methyl-1-pentylpyrrolidinium

9.865

-0.512

-11.236


10.327

-0.508

-12.793


11.633

-0.500

-13.698


9.938

-0.369

-11.478

1,1-dipropyl-pyrrolidinium

9.966

-0.370

-11.489

1-(2-ethoxyethyl)-1-methylpyrrolidinium

9.857

-0.783

-11.100


7.887

-7.956

-10.996


8.100

-7.404

-11.150 -11.022

di-ethyl-di-isopropylammonium

8.012

-7.570

diethanolammonium

6.305

-12.091

-7.459


7.104

-6.712

-6.996


12.307

-0.322

-15.636

ethyl-dimethyl-2-methoxyethylammonium

9.360

-0.920

-9.777

24


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ethyl-dimethyl-propylammonium

9.090

-0.694

-9.338


9.897

-0.796

-10.987


11.060

-0.364

-15.012


11.632

-0.353

-15.363


11.704

-0.337

-15.700

tetra-methylammonium

8.011

-1.148

-6.624

trimethylethylammonium

8.403

-0.921

-7.479


9.043

-0.904

-9.542


9.993

-0.896

-11.066

heptyltrimethylammonium

10.656

-0.886

-12.365

octyltrimethylammonium

10.458

-0.874

-13.789


11.963

-0.360

-14.963


9.795

-0.510

-11.317

1-(3-methoxypropyl)-1-methylpiperidinium

10.324

-1.088

-11.767

guanidinium

2.452

-16.100

-3.965


9.207

-1.627

-10.531

choline

9.024

-10.697

-8.533


10.637

-7.563

-10.337

25



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Page 26 of 31

Table 3. COSMO-RS volume, misfit, hydrogen-bonding and van der Waals energies for the capacity of DBT in the [DBP]-based ILs combinations at 298.15 K Ionic Liquid Cation

EMF (kcal/mol)

EHB (kcal/mol)

EVdW (kcal/mol)

3-methyl-imidazolium

5.921

-9.188

-7.222

1-butyl-imidazolium

6.561

-9.082

-9.247


7.255

-3.216

-7.376


7.602

-3.106

-8.354

1-propyl-3-methyl-imidazolium

7.857

-3.093

-9.753

1-butyl-3-methyl-imidazolium

8.282

-3.071

-10.469


8.414

-3.065

-10.767


8.687

-3.072

-11.928

1-heptyl-3-methyl-imidazolium

9.255

-3.082

-12.797

1-octyl-3-methyl-imidazolium

9.650

-3.086

-14.676


10.427

-3.096

-15.533


11.638

-3.093

-16.923

1-dodecyl-3-methyl-imidazolium

12.367

-3.082

-19.202

1-hexadecyl-3-methyl-imidazolium

12.429

-3.081

-23.099


7.366

-3.106

-9.522


8.293

-3.073

-10.488


8.527

-3.056

-10.930

1-methyl-pyridinium

7.358

-2.981

-7.797

1-ethyl-pyridinium

7.493

-2.965

-8.117

1-butyl-pyridinium

8.165

-2.924

-10.214

1-hexyl-pyridinium

8.638

-0.721

-11.798

1-octyl-pyridinium

10.091

-0.705

-11.898 -10.746

1-butyl-3-ethyl-pyridinium

8.767

-0.758

1-ethyl-3-methylpyridiniumcosmo

8.012

-1.483

-9.127


8.665

-1.449

-11.155


9.422

-0.671

-11.823

3-methyl-1-octyl-pyridinium

10.387

-0.570

-12.264

benzyl-triphenyl-phosphonium

11.903

-1.177

-19.056


7.964

-0.911

-7.919


8.377

-0.907

-8.500


9.025

-0.892

-10.582

1-methyl-1-pentylpyrrolidinium

9.267

-0.880

-11.133


9.728

-0.877

-12.691


11.034

-0.869

-13.596


9.339

-0.738

-11.376

1,1-dipropyl-pyrrolidinium

9.367

-0.739

-11.386

1-(2-ethoxyethyl)-1-methylpyrrolidinium

9.258

-1.152

-10.998


7.288

-13.480

-10.894


7.501

-12.927

-11.048 -10.920

di-ethyl-di-isopropylammonium

7.413

-13.093

diethanolammonium

5.707

-17.614

-7.357


6.505

-12.235

-6.894


11.708

-0.620

-15.533

ethyl-dimethyl-2-methoxyethylammonium

8.762

-1.218

-9.690

26


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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


ethyl-dimethyl-propylammonium

8.491

-0.993

-9.251


9.298

-1.095

-10.900


10.461

-0.663

-14.925


11.034

-0.651

-15.276


11.105

-0.635

-15.613

tetra-methylammonium

7.413

-1.446

-6.537

trimethylethylammonium

7.804

-1.220

-7.392


8.444

-1.202

-9.455


9.394

-1.195

-10.979

heptyltrimethylammonium

10.057

-1.184

-12.278

octyltrimethylammonium

9.860

-1.173

-13.702


11.364

-0.659

-14.876


9.197

-0.809

-11.230

1-(3-methoxypropyl)-1-methylpiperidinium

9.725

-1.387

-11.680

guanidinium

1.853

-26.955

-3.878


8.608

-4.699

-10.444

choline

8.425

-21.036

-8.446


10.038

-10.687

-10.250

27



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Page 28 of 31

Table 4. COSMO Descriptor HB_acc3 for Typical Anions

acetate decanoate

anion

HB_acc3 38.928 38.072

anion hydrogensulfate dimethylphosphate

HB_acc/don3 18.404/3.246 34.453

bismalonatoborate

11.018

diethylphosphate

35.883

bisoxalatoborate

3.0293

dibutylphosphate

35.964

bissalicylatoborate methylsulfate

12.591 18.344

dihydrogen-phosphate bf4

35.465/4.827 2.487

ethylsulfate

19.179

pf6

0

butylsulfate

18.975

tf2n

2.292

octylsulfate methoxyethylsulfate

18.995 20.340

asf6 tetracyanoborate

0 3.453

ethoxyethylsulfate

20.463

dicyanamide

15.666

2-(2-methoxyethoxy)ethylsulfate

22.757

thiocyanate

12.291

trifluoromethane-sulfonate toluene-4-sulfonate

10.684 25.650

dicyano(nitroso)methanide cl

7.968 36.627

methanesulfonate

30.085

br

29.644

28


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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


Table 5. COSMO-RS volume, misfit, hydrogen-bonding and van der Waals energies for the capacity of TS in the [C2mim]-based ILs combinations at 298.15 K EMF (kcal/mol)

EHB (kcal/mol)

acetate

Ionic Liquid Anion

EVdW (kcal/mol)

3.329

-6.912

-4.446

decanoate

5.948

-9.804

-12.814

bismalonatoborate

1.283

-1.940

-2.714

bisoxalatoborate

2.330

-0.585

-8.149

bissalicylatoborate

4.926

-1.776

-14.340

methylsulfate

2.774

-2.407

-5.802

ethylsulfate

3.173

-2.509

-6.887

butylsulfate

3.826

-2.500

-8.949

octylsulfate

5.213

-2.502

-13.167

methoxyethylsulfate

4.064

-2.567

-8.457

ethoxyethylsulfate

4.363

-2.568

-9.559


5.616

-2.899

-11.206

trifluoromethane-sulfonate

1.749

-1.449

-5.516

toluene-4-sulfonate

4.573

-3.558

-9.618

methanesulfonate

3.493

-5.883

-5.271

hydrogensulfate

2.403

-11.056

-4.606

dimethylphosphate

4.166

-4.386

-7.047

diethylphosphate

4.919

-6.234

-9.308

dibutylphosphate

6.244

-6.154

-13.469

dihydrogen-phosphate

3.738

-19.786

-4.679

bf4

1.195

-1.258

-3.432

pf6

0.813

-0.319

-4.326

tf2n

2.184

-0.468

-8.507

asf6

0.746

-0.188

-4.585

tetracyanoborate

1.728

-0.587

-6.441

dicyanamide

1.697

-2.256

-4.114

thiocyanate

1.566

-1.819

-4.905

dicyano(nitroso)methanide

1.703

-0.985

-5.427

cl

2.964

-6.326

-3.249

br

2.816

-5.912

-3.743

29



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Page 30 of 31

Table 6. COSMO-RS volume, misfit, hydrogen-bonding and van der Waals energies for the capacity of DBT in the [C2mim]-based ILs combinations at 298.15 K. EMF (kcal/mol)

EHB (kcal/mol)

acetate

Ionic Liquid Anion

EVdW (kcal/mol)

2.679

-19.809

-4.413

decanoate

5.385

-19.422

-12.725

bismalonatoborate

3.844

-3.553

-9.625

bisoxalatoborate

2.223

-0.898

-8.061

bissalicylatoborate

4.653

-3.039

-14.180

methylsulfate

2.488

-4.214

-5.749

ethylsulfate

2.893

-4.423

-6.826

butylsulfate

3.569

-4.406

-8.873

octylsulfate

4.988

-4.412

-13.063

methoxyethylsulfate

3.732

-4.513

-8.378

ethoxyethylsulfate

4.058

-4.521

-9.471


5.191

-5.146

-11.098

trifluoromethane-sulfonate

1.646

-2.428

-5.469

toluene-4-sulfonate

4.143

-6.762

-9.519

methanesulfonate

2.994

-12.549

-5.226

hydrogensulfate

2.020

-11.808

-4.572

dimethylphosphate

3.591

-12.523

-6.990

diethylphosphate

4.360

-13.365

-9.238

dibutylphosphate

5.727

-13.174

-13.369

dihydrogen-phosphate

2.907

-24.727

-4.657

bf4

1.089

-2.024

-3.345

pf6

0.809

-0.464

-4.251

tf2n

2.211

-0.708

-8.440

asf6

0.759

-0.268

-4.511

tetracyanoborate

1.729

-0.922

-6.453

dicyanamide

1.507

-4.110

-4.115

thiocyanate

1.385

-3.351

-4.822

dicyano(nitroso)methanide

1.652

-2.315

-5.368

cl

2.324

-13.323

-3.248

br

2.359

-12.890

-3.354

30


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Table of Contents (TOC) Graphic

For Table of Contents Only

31


Desulfurization of Fuel Oil: Conductor-like Screening

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