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Energy & Fuels 2008, 22, 1774–1778
[bmim]AlCl4 Ionic Liquid for Deep Desulfurization of Real Fuels Roland Schmidt ConocoPhillips, BartlesVille Technology Center, BartlesVille, Oklahoma 74004 ReceiVed NoVember 30, 2007. ReVised Manuscript ReceiVed February 21, 2008
1-Butyl-3-methylimidazolium tetrachloroaluminate ionic liquid (IL) was synthesized and tested for its capability to extract organic sulfur species from real, refinery obtained hydrocarbon fuels. The fuels consisted of sulfur-rich gasoline and diesel as well as pretreated, partially desulfurized gasoline and diesel. The ILextracted fuels were then analyzed for total sulfur, nitrogen, and chlorine. Total sulfur was significantly lowered in all tested fuels. Nitrogen levels were also significantly reduced mainly due to a pretreatment with molecular sieve. Only traces of chloride originating from the IL could be detected in three of the four samples after all extraction stages. Sulfur-speciation analyses revealed that some sulfur compounds in the feed were converted to new compounds.
1. Introduction
studies tested IL’s on real gasoline and/or diesel samples15–17 and various IL’s.18,19
Ionic liquids are mixtures of salts with low melting points. Because of their salt-like characteristics, they are nonvolatile and nonflammable and exhibit a high ionic conductivity. The liquid phase is found over a wide temperature range up to 300 °C. IL’s are generally highly solvating and noncoordinating.1–6 Both the cations and anions of the salt determine the physical properties (e.g., melting point, viscosity, density, solubility, etc.). For cations organic salt-forming compounds (e.g., pyridine, imidazole, etc.) are often chosen. The anion moiety often consists of inorganic anion-forming components (AlCl3, BF3, AgBF4, etc.). Depending on the ratio of cation/anion the IL can be Lewis-acidic, neutral, or Lewis-basic.7 Recently, ionic liquids were found to be effective in the desulfurization of model diesel fuels (dibenzothiophene(DBT)/n-dodecane) under mild conditions.8–14Other
Because of new and stringent regulations, desulfurizing of fuels has become increasingly important to the petroleum industry. In refineries, hydrotreating is a commonly used method to reduce sulfur in fuels. Unfortunately, the associated costs (e.g., equipment and hydrogen) are high. Newly developed methods20–25 can also achieve deep desulfurization of gasoline but are less effective for diesel fuels. Certain sulfur compounds in diesel are less prone to react and remain in the fuel. An associated problem is the cross-contamination of fuels during pipeline transportation. Low sulfur fuels that exit a pipeline at terminals may contain unacceptable high sulfur levels. Thus, an effective and easily applicable method needs to be found that can lower or remove sulfur-containing compounds while not affecting the fuel properties themselves. Extracting these sulfur compounds from true fuels with IL’s could offer such a solution.26 This publication reports in detail the denitrification
(1) Welton, T. Chem. ReV. 1999, 99, 2071–2083. (2) Forsyth, S. A.; Pringle, J. M.; MacFarlane, D. R. Chem. ReV. 1999, 99, 2071–2083. (3) Wilkes, J. S. J. Mol. Catal. A: Chem. 2004, 214, 11–17. (4) Visser, A. E.; Holbrey, J. D.; Rogers, R. D. Proceedings of the International Solvent Extraction Conference, Cape Town, South Africa, March 17-21, 2002. (5) Sole, K. C.; Cole, P. M.; Preston, J. S.; Robinson, D. J. Chris van Rensburg Publications: Melville, South Africa, 2002; Vol. 1; pp 474480. (6) Rogers, R. D.; Seddon, K. R. ACS Symposium Series 818; American Chemical Society: Washington, DC, 2002. (7) Davis, J. H.; Gordon, C. M.; Hilgers, C.; Wasserscheid, P. In Ionic Liquids in Synthesis; Wasserscheid, P., Welton, T., Eds.; Wiley-VCH: New York, 2003; Chapter 2. (8) Boesmann, A.; Datsevich, L.; Jess, A.; Schmitz, C.; Wasserscheid, P. Chem. Commun. 2001, 2494–2495. (9) Esser, A.; Jess, A.; Wasserscheid, P. Chem.-Ing.-Tech. 2003, 75, 1149–1150. (10) Zhang, S.; Zhang, Z. C. Green Chem. 2002, 4, 376–379. (11) Ko, N.; Nanhee, E.; Eunsoo, C.; Cheong, H. S.; Kim, B. S.; Ahn, B. S. Abstracts of Papers, 234th ACS National Meeting, Boston, MA, Aug 19-23, 2007; IEC-059. (12) Jess, A.; Esser, J. Proc. Electrochem. Soc. 2006, 572–582, 200424 (Molten Salts XIV) (13) Lu, L.; Cheng, S.; Gao, J.; Gao, G.; He, M.-Y. Energy Fuels 2007, 21, 383–384. (14) Zhu, W.; Li, H.; Jiang, X.; Yan, Y.; Lu, J.; Xia, J. Energy Fuels 2007, 21, 2514–2516.
(15) Jess, A.; Wasserscheid, P.; Esser, J. Chem.-Ing.-Tech. 2004, 76, 1407–1408. (16) Zhang, S.; Zhang, Q.; Zhang, Z. C. Ind. Eng. Chem. Res. 2004, 43, 614–622. (17) Huang, C.; Chen, B.; Zhang, J.; Liu, Z.; Li, Y. Energy Fuels 2004, 18, 1862–1864. (18) Hilgers, C.; Uerdingen, M.; Jess, A.; Esser, J.; Wasserscheid, P.; Sitsen, P. Abstracts of Papers, 231st ACS National Meeting, Atlanta, GA, March 26-30, 2006; IEC-206. (19) Esser, J.; Wasserscheid, P.; Jess, A. Green Chem. 2004, 6, 316– 322. (20) Greenwood, G.; Kidd, D.; Gislason, J.; Slater, P. Proceedings of the 17th World Petroleum Congress, 2002; Vol. 3; pp 297-304. (21) Yun, X.; Long, J.; Shao, X. China Pet. Process. Petrochem. Technol. 2003, 19–23. (22) Germana, G.; Abbott, D.; Turaga, U. Hydrocarbon Eng. 2004, 9, 35–38. (23) Slater, P. N.; Johnson, B. G. Pre-Print ArchivesAmerican Institute of Chemical Engineers, Spring National Meeting, New Orleans, LA, Mar 11-14, 2002; pp 1102-1110. (24) Gislason, J. Hydrocarbon Eng. 2002, 7, 39–40,42. (25) Covert, C.; Shepherd, T. C.; Thompson, M. W. World Refin. 2001, 11, 60–61. (26) Jess, A.; Wasserscheid, J.; Esser, J. DGMK Tagungsber. 2003, 20032, 313–320. (Proceedings of the DGMK-Conference “Innovation in the Manufacture and Use of Hydrogen”, 2003)
10.1021/ef7007216 CCC: $40.75 2008 American Chemical Society Published on Web 04/09/2008
Deep Desulfurization of Real Fuels
Energy & Fuels, Vol. 22, No. 3, 2008 1775 Table 2. Partially Desulfurized Gasoline before and after Extraction with ILa
Figure 1. One possible structure of n-butyl-N-methylimidazolium tetrachloroaluminate. Table 1. Total Sulfur and Nitrogen Content of the Fuel Samples (IL/Fuel ) 1/6, Room Temperature Extraction) no.
description
stage
sulfur (ppm)
nitrogen (ppm)
1 2
regular diesel feed regular diesel feed; dried with molsieve regular diesel feed regular diesel feed regular diesel feed regular diesel feed treated diesel treated diesel; dried with molsieve treated diesel treated diesel treated diesel treated diesel regular gasoline feed regular gasoline feed; dried with molsieve regular gasoline feed regular gasoline feed regular gasoline feed regular gasoline feed treated gasoline treated gasoline; dried with molsieve treated gasoline treated gasoline treated gasoline treated gasoline
0 0-1
2737.07 2233.82
139.95 9.21
1 2 3 4 0 0-1
1060.4 485.98 256.91 129.15 69.69 48.27
1.89 0.66 0.39 0.87 131.14 11.92
1 2 3 4 0 0-1
38.03 26.02 17.49 11.56 4254.13 4119.57
0.84 0.48 1 0.95 38.84 1.52
1 2 3 4 0 0-1
613.49 502.59 365.11 239.08 168.92 162.04
1.86 0.86 1.07 0.91 42.13 1.87
91.93 99.81 92.55 82.33
2.43 2.11 2.23 1.99
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1 2 3 4
of real fuels with [bmim]AlCl4 IL as well as the sulfur speciation before and after multiple stage extraction with said IL. 2. Results and Discussion Untreated gasoline and diesel samples as well as partially desulfurized gasoline (treated) and diesel with different levels of sulfur were extracted with n-butyl-N-methylimidazolium tetrachloroaluminate (Figure 1). The fuels were dried prior to use with activated 13X molecular sieve in order to prevent decomposition of the IL to form HCl. Each fuel was then added to freshly prepared IL in an initial volume ratio of 1/6 (10 mL of IL/60 mL of fuel). The two-phase mixture was vigorously stirred for 5 min at room temperature, after which it was allowed to separate. In all cases, the dark green IL turned black immediately when it contacted the fuels. The diesel samples needed up to 30 min for complete separation, whereas the gasoline samples separated in less than 3 min. This effect is probably due to the differences in density between the fuels and the IL. The synthesized IL has a density of ∼1.19 g/mL, which is closer to that of diesel (0.82-0.95 g/mL) than gasoline 0.71-0.74 g/mL). This process was repeated four times. Each time, the fuel from the previous extraction was added to a fresh sample of IL. Also, in each stage a fuel sample of 2.5 mL was collected for chemical analysis (see below). Total sulfur and nitrogen content was determined by ANTEK (Table 1). The drying step with 13X molsieve removed >90% and >95% of all nitrogen compounds in the diesel and gasoline, respectively. The first IL extraction removed virtually all the remaining nitrogen-containing compounds (Figure 2). The
SZorb gas 0 stage forms of sulfur C3 sulfides thiophene C1 thiophenes C2 thiophenes C3 thiophenes C4 thiophenes C6 thiophenes other sulfur species ND ND ND ND ND ND
ppm 1.69 113.23 26.00 22.15 12.17 6.41 3.74 1.74
SZorb gas 4 stage forms of slfur
ppm
ND ND ND ND ND ND C6 thiophenes other sulfur species C1 benzothiophenes C2 benzothiophenes C3 benzothiophenes C4 benzothiophenes C5 benzothiophenes C6 benzothiophenes
0.71 3.84 0.55 11.13 11.26 8.02 5.42 4.96
a Labeled in italics ) new species, ND ) not detected. IL/fel ) 1/6, room temperature extraction. “CX”: X refers to an alkyl group at position X on the sulfur compound.
molsieve also removed some of the sulfur species but was not nearly as efficient as it was at removing nitrogen-containing compounds. In each stage of the diesel extraction, the IL steadily lowered the sulfur content. However, for gasoline only the first stage significantly reduced the sulfur content. Sulfur loss per stage varied depending on the fuel tested. Untreated (regular) diesel lost an average of 50% sulfur per stage (total sulfur removal 94.2%) while partially desulfurized diesel lost only about 30% per stage (total sulfur removal 76.1%). In the case of untreated gasoline, the first stage removes 85%, but the subsequent stages each take out only an average of 25% (18%, 27%, and 34%; total sulfur removal 94.2%). The first extraction partially desulfurized gasoline removed 43%. The following stages eliminated only additional ca. 10% per stage (total sulfur removal 49.2%; Figures 3 and 4). 2.1. Sulfur Speciation before and after. In order to determine whether these differences can be correlated to certain sulfur species, the initial fuels and the last extraction stage were analyzed by forms of sulfur (sulfur speciation) (see Tables 2–5). In the case of partially desulfurized gasoline (Table 2), almost no thiophenes (only C6 thiophenes) and no sulfides were detected. The amount of C2 dihydrobenzothiophene was 4 times higher in the final product than in the original gasoline most likely due to a Lewis-acid-catalyzed Diels-Alder reaction. Similarly, in the case of untreated gasoline (Table 3), all sulfur species were affected as well and mostly quantitatively removed in the final product (sulfides, thiols, C1-C5 thiophenes, dihydrobenzothiophenes, tetrahydrothiophenes, and disulfides). On the other hand, some C4 benzothiophenes and C3+ dibenzothiophenes were found that were not present in the original sample. This behavior may result from a Lewis-acid-catalyzed Diels-Alder reaction due to excess AlCl3 and may have been further facilitated by the presence of sulfur as a dienophile activating electronegative heteroatom.27,28 The AlCl3 can form a complex with the dienophile and thus activate it further. A [4 + 2] cycloaddition reaction of the dienophile with a diene may occur even under the conditions of the experiment.1,29–31 The (27) Rickborn, B. The Retro-Diels-Alder Reaction. Part II. Dienophiles with One or More Heteroatom; John Wiley & Sons: New York, 1998; Vol. 53, pp 223-629. (28) Seitz, G.; Kaempchen, T. Chem.-Ztg. 1975, 99, 292. (29) Yates, P.; Eaton, P. J. Am. Chem. Soc. 1960, 82, 4436. (30) Fray, E. I.; Robinson, R. J. Am. Chem. Soc. 1961, 83, 249.
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Figure 2. Removal of nitrogen-containing compounds by molsieve and IL. IL/fuel ) 1/6, room temperature extraction.
Figure 3. Four-stage extraction of untreated diesel and gasoline. IL/fuel ) 1/6, room temperature extraction.
Figure 4. Four-stage extraction of partially desulfurized diesel and gasoline. IL/fuel ) 1/6, room temperature extraction.
required dienes must have been present in both gasolines. GC/ MS spectra taken from all used gasoline samples at all stages indicated that many different dienes were present. Pretreated diesels (Table 4) showed a somewhat different picture. Most sulfur species were quantitatively removed. Only the most sterically hindered species, 4,6-dimethyldibenzothiophene and C3+ dibenzothiophenes, were removed only to 83% and 75%, respectively. No other sulfur species were detected. A similar result was found in the case of untreated diesel (Table 5). All sulfur species were significantly affected by the (31) Zhao, H.; Malhotra, S. V. Aldrichim. Acta 2002, 35, 75–83.
IL extraction. Most of them were removed by 90-100%. The remaining sulfur species were all of aromatic nature. As seen before, the more sterically hindered the species, the less of it that was extracted. 2.2. IL Sulfur Species Reactivity in Fuels: Advantage or Disadvantage? Different sulfur species reacted differently to the extraction treatment with IL. Some sulfur compounds were removed completely while others were altered. When the gasoline samples were treated with the IL, the newly formed species consisted primarily of benzothiophenes. In contrast to the gasolines, diesels did not show any formation of new sulfur species. This result is most likely due to the
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Table 3. Untreated Gasoline before and after Extraction with ILa reg gas 0 stage forms of sulfur
ppm
C3 sulfides 3.60 C6+ thiols 8.42 thiophene 382.40 C1 thiophenes 106.97 C2 thiophenes 107.93 C3 thiophenes 98.74 C4 thiophenes 64.28 C5 thiophenes 19.33 C6 thiophenes 7.47 benzothiophene 98.44 C1 benzothiophenes 150.12 C2 benzothiophenes 82.29 C3 benzothiophenes 24.27 tetrahydrothiophene 9.46 ND C1 tetrahydrothiophenes 5.69 C4 tetrahydrothiophenes 2.45 dihydrobenzothiophene 6.12 C1 dihydrobenzothiophenes 1.45 C2 dihydrobenzothiophenes 10.86 C4 disulfides 29.61 ND C2 disulfide (methyl disulfide) 4123.6
reg gas 4 stage forms of sulfur
ppm
ND ND ND ND ND ND ND ND C6 thiophenes 0.35 ND C1 benzothiophenes 1.12 C2 benzothiophenes 3.30 C3 benzothiophenes 5.44 ND C4 benzothiophenes 6.03 ND ND ND C1 dibenzothiophenes 63.90 ND ND C3+ dibenzothiophenes 7.29 ND
a Labeled in italics ) new species. ND ) not detected. IL/fuel ) 1/6, room temperature extraction. “CX”: X refers to an alkyl group at position X on the sulfur compound.
Table 4. Partially Desulfurized Diesel before and after Extraction with ILa SZorb diesel 0 stage
ppm
C1 benzothiophenes C2 benzothiophenes C3 benzothiophenes C4 benzothiophenes dibenzothiophene C1 dibenzothiophenes 4-methyldibenzothiophene C2 dibenzothiophenes 4,6-Dimethyldibenzothiophene C3+ Dibenzothiophenes
0.39 1.47 2.22 1.26 0.93 2.41 1.43 18.16 16.43 31.45
SZorb diesel 4 stage
ppm
ND ND ND ND ND ND ND ND 4,6-dimethyldibenzothiophene 2.86 C3+ dibenzothiophenes 7.93
a ND ) not detected. IL/fuel ) 1/6, room temperature extraction. “CX”: X refers to an alkyl group at position X on the sulfur compound.
lack of appropriate (di-)olefinic hydrocarbons in the feed that could induce a Diels-Alder reaction. With the removal of much of the sulfur and many of the sulfur species, the remaining ones may be easier to remove if necessary and required by new regulations. 2.3. Effects of the IL Extraction on Fuel Properties. Under the stated conditions, saturated hydrocarbons remain normally unaffected by the treatment with acidic IL’s. The investigated IL showed similar behavior as indicated by GC/MS data. In all stages the fuel compositions appear to be virtually unchanged except for the fact that sulfur species were removed. The octane rating was also virtually unchanged. The amount of dienophils consumed for the before mentioned Diels-Alder reaction did not negatively affect the octane rating of the final product. The use of this particular type of IL has some unique features. Besides being highly (Lewis) acidic and thus water sensitive, it contains a significant amount of chloride ions stemming from the synthesis of the IL’s cationic moiety with butyl chloride as well as from the use of AlCl3. Chlorine and chlorides normally should be avoided in refinery operations due to their corrosive nature. Furthermore, the Lewis acid AlCl3 most likely promotes the observed shift in sulfur species caused by a Diels-Alder reaction.
In order to determine the source of the chloride found in the treated fuels, the total amount of chloride accumulated in the fourth and last stage of the extraction was analyzed (Table 6). With n-butyl chloride in isooctane as the chloride calibration standard, the analysis did not show n-butyl chloride in any of the samples. The detected chloride must therefore have originated from other sources, indicating that the used IL was the source since no chloride was found in the untreated fuels. These retained chlorides must be removed prior to fuels distribution. 3. Conclusions The ionic liquid tested effectively removed sulfur-containing species from the fuels studied. The denitrification observed was mainly due to the use of 13X molecular sieve in the drying step, not the ionic liquid.32 Sulfur removal efficiency was dependent on the fuel (gasoline or diesel) and the number of extraction stages employed. All sulfur species present in the fuels were removed to a significant degree (see Tables 2–5). Only the most sterically hindered sulfur species were found remaining in the diesel fuels after all four extractions. After the fourth stage extraction some chloride was detected in three out of the four fuels tested. The most probable source of this chloride was from decomposition of the anion of the IL despite the experiments being conducted at room temperature and atmospheric pressure in sealed, nitrogen-filled vials. GC/ MS analysis showed no effect on the major fuel components. Thus, it can be expected that the overall fuel properties were unaffected. A potential disadvantage of this particular IL is its sensitivity toward water and possible difficulties associated with its regeneration. Although no attempt to regenerate the ionic liquid was attempted here, literature offers some regeneration techniques33–36 such as the use of supercritical CO237 or light hydrocarbons, e.g., isobutane.38 The results indicate that ionic liquids might be complementary to existing sulfur removal technologies and could be applied where small-scale desulfurization is necessary. 4. Experimental Section a. Synthesis of the Ionic Liquid (IL). In a 1 L three-neck flask under nitrogen, 200 mL of N-methylimidazolium was added to 500 mL of n-butyl chloride. Both were obtained from SigmaAldrich and used without further purification. The mixture was refluxed for ca. 30 min, after which a second phase formed. To complete the reaction, the mixture was continuously refluxed for 7 h. Excess n-butyl chloride was distilled off in vacuum at elevated temperature. The remaining phase crystallized after 3 days at -20 °C. (32) Zhang, S.; Zhang, Q.; Zhang, Z. C. Ind. Eng. Chem. Res. 2004, 43, 614–622. (33) Beste, Y. A.; Schoenmakers, H.; Wolfgang, W.; Seiler, M.; Jork, C. Carsten. Ger. Offen. DE 10336555 A1 20050224, 2005; 23 pp. (34) Nie, Y.; Li, C.-X.; Wang, Z.-H. Ind. Eng. Chem. Res. 2007, 46, 5108–5112. (35) Jeapes, A. J.; Thied, R. C.; Seddon, K. R.; Pitner, W. R.; Rooney, D. W.; Hatter, J. E.; Welton, T. PCT Int. Appl WO 200101 5175 A2 20010301, 2001. (36) Zhao, D.; Dishun, W.; Jianlong, Z.; Zhou, E. Abstracts of Papers, 232nd ACS National Meeting, San Francisco, CA, Sept 10-14, 2006; FUEL-248. (37) Yoon, B.; Yen, C. H.; Mekki, S.; Wherland, S.; Wai, C. M. Ind. Eng. Chem. Res. 2006, 45, 4433–4435. (38) Ginosar, D. M.; Thompson, D. N.; Anderson, R. P. U.S. Pat. Appl. Publ. US 2004063567 A1 20040401, 2004; 18 pp.
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Table 5. Untreated Diesel before and after Extraction with ILa
a
reg diesel 0 stage
ppm
reg diesel 4 stage
C6+ sulfides C5 thiophenes C6 thiophenes benzothiophene C1 benzothiophenes C2 benzothiophenes C3 benzothiophenes C4 benzothiophenes C5 benzothiophenes C6 benzothiophenes C1 dihydrobenzothiophenes C2 dihydrobenzothiophenes dibenzothiophene C1 dibenzothiophenes 4-methyldibenzothiophene C2 dibenzothiophenes 4,6-Dimethyldibenzothiophene C3+ dibenzothiophenes
821.17 1.54 4.40 4.99 73.27 228.98 307.69 180.89 114.59 92.35 0.61 6.12 78.36 289.78 118.12 370.01 50.67 357.54
ND ND ND ND ND C2 benzothiophenes C3 benzothiophenes C4 benzothiophenes C5 benzothiophenes C6 benzothiophenes ND ND dibenzothiophene C1 dibenzothiophenes 4-methyldibenzothiophene C2 dibenzothiophenes 4,6-dimethyldibenzothiophene C3+ dibenzothiophenes
ppm
1.03 0.70 0.80 0.96 1.77 3.07 13.36 7.30 28.68 6.29 48.43
ND ) not detected. IL/fuel ) 1/6, room temperature extraction. “CX”: X refers to an alkyl group at position X on the sulfur compound.
To 125 g of the obtained n-butyl-N-methylimidazolium chloride, 175 g of dry AlCl3 was added in small portions. The flask was cooled to 0 °C during the addition due to the exothermic reaction while forming the ionic liquid. N-Butyl-N-methylimidazolium tetrachloroaluminate was obtained as a dark green liquid. The IL is filtered through a glass-frit filled with glass wool to remove traces of solids. No further purification was attempted. The IL was then transferred into a glovebox for storage. b. Sulfur Removal from Diesel and Gasoline Samples. The fuels were dried with activated 13X molecular sieve prior to use. For each fuel, in a glovebox, four 100 mL vials were filled with 10 mL of IL and capped. 60 mL of a fuel was added to an IL-filled vial via a syringe. The two-phase system was stirred for 5 min at room temperature. After phase separation, the fuel was transferred over via a syringe into a fresh IL-filled vial, and the procedure was repeated to a total of four extractions for each fuel. Total Nitrogen and Sulfur Analysis. Total nitrogen analysis was conducted using an Antek 9000NS analyzer. The sample is vaporized and combined with oxygen at 1100 °C. The oxidation of the sample results in the conversion of the chemically bound nitrogen to NO and of sulfur to SO2. The combustion gases are routed through a membrane to remove any water before entering the sulfur detector for analysis. The SO2 is exposed to ultraviolet radiation of a specific wavelength. The fluorescent emission is proportional to the amount of sulfur in the original sample. The gas then enters the nitrogen detector where it is contacted with ozone. The NO in the sample is converted to NO2. As the metastable species decays, a photon of light is emitted and detected by a photomultiplier tube. This fluorescent emission is proportional to the amount of nitrogen in the original sample. The signals are compared to internal calibration curves from nitrogen/sulfur standards with known concentrations. Sulfur Speciation. This method is for the determination of sulfur compounds in liquid hydrocarbon sample boiling below 260 °C
Table 6. Chloride Content of the Tested Fuels after Four Extractions with IL sample description
chloride concentration (µg Cl/mL)
n-butyl chloride detected
diesel pretreated diesel gasoline pretreated gasoline
0 34 31 34
no no no no
using capillary column gas chromatography (GC) with a sulfur chemiluminescense detector (SCD). The detection limit for any single component is ∼0.1 ppm of sulfur by weight, depending on the amount of sample injected and sample characteristics. For this method an Agilent 6890 GC-FID with a Siever model 355 SCD sulfur-specific detector was used. The column was a methylsilicone fused silica capillary column with the dimensions 30 m × 0.53 mm × 2.66 µm. A split ratio was set such that 75 ppm total sulfur from methyl disulfide was
