Distribution and Qualitative and Quantitative Analyses of Chlorides in

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Distribution and Qualitative and Quantitative Analyses of Chlorides in Distillates of Shengli Crude Oil Rui Ma,† Jianhua Zhu,*,† Bencheng Wu,† Jigen Hu,‡ and Xiaohui Li§ †

College of Chemical Engineering, China University of Petroleum, Beijing 102249, People’s Republic of China Henan Beijia Lubrication Science & Technology Company, Limited, Luohe, Henan 462003, People’s Republic of China § College of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an, Shanxi 710065, People’s Republic of China ‡

S Supporting Information *

ABSTRACT: This work investigated the distribution of the chlorine element in Shengli (SL) crude oil using a microcoulomb titrameter and a salt content determinator. The species and contents of organic chlorides in light distillates (bp < 300 °C) were determined by gas chromatography equipped with an electron capture detector (GC−ECD). The content of organic chloride in SL crude oil was 188.68 mg/L, and organochlorine compounds were found in each distillate of SL crude oil. The contents of organochlorine in naphtha, kerosene, and light diesel were measured as 302.93, 729.45, and 836.90 mg/L, respectively. The species of organic chlorides that existed in naphtha, kerosene, and light diesel were similar. Trichloroethylene, 3-chloro-2methylaniline, 5-chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline were all identified in the three types of light distillates of SL crude oil. The gas chromatography quantitative analysis results of organic chlorides in light distillates (bp < 300 °C) illustrated that a large proportion of organic chlorides has been identified, in which 5-chloro-2-methylaniline was the dominate species.

1. INTRODUCTION The organochlorine compounds in crude oil can be catalogued into two types: one type is the naturally occurring,1 and another type is artificially added during the processes of crude oil exploitation,2 transportation,3 and refining.4 Organic chlorides tend to spontaneously hydrolyze and convert into hydrogen chloride (HCl) during the crude oil distillation process. HCl can dissolve in a tiny amount of water and generate a dilute hydrochloric acid solution, which, in turn, results in serious problems, such as corrosion, on the top section of the atmospheric distillation column and overhead condensing system.5−7 Moreover, in the pre-hydrogenation processes of hydrocarbon reforming, diesel hydrogenation, and jet fuel hydrogenation, HCl generated from organic chlorides can react with NH3 formed by the hydrogenation of nitrogen compounds to form ammonium chloride (NH4Cl), which causes serious blockage to the heat exchanger4 and under-deposit corrosion,8 thereby threatening the long period operation of the equipment. In addition, high concentrations of organic chloride in the fuel would be a potential threat to the engine and quality of the atmosphere. Therefore, it is necessary to investigate the distribution and occurrence states of chlorine in crude oil and/or its distillates. The investigation results could help to predict the position of chlorine corrosion and ammonium chloride deposition, discover the origin of the illegal addition of organic chlorides, and guide the implementation of targeted measures. Moreover, it is useful for the development of adsorption and hydrogenation dechlorination technology.9 Until now, few studies have been conducted on the distribution and occurrence states of chloride in crude oil and/or its distillates. Wu et al.9 reported the distribution of organochlorine elements in YS crude oil and presented the © 2016 American Chemical Society

dumbbell distribution model for organochlorine, because the organic chlorides were mainly enriched in the naphtha and vacuum residue. Zhang2 studied the distribution of organochlorine in a specified piped crude oil, which also presented a similar distribution rule; i.e., the organic chlorides were mainly enriched in the naphtha and atmospheric residue. Previous studies mainly focused on the occurrence states of organic chlorides in naphtha, and it is hard to find investigations into the occurrence states of organic chlorides in kerosene and light diesel. In this work, the organochlorine compounds in Shengli (SL) crude oil were mainly concentrated in the kerosene and light diesel distillates, which had not yet been reported. Several organic chlorides have been identified from crude oil and its distillates, such as 1,2-dichlorobenzene, 1,1,2,2-tetrachloroethane, carbon tetrachloride, trichloromethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, 1,2,3-trichloropropene, 1,2,4-trichlorobenzene, 1,1,1,3-tetrachloropropane, hexachloroethane, 3-chloropropene, and dichloromethane.4,9−12 The boiling point of 1,2,4-trichlorobenzene (214 °C) was the highest among the identified organic chlorides, and more higher boiling point organic chlorides, which have not been identified from crude oil by other researchers, were detected in this work. The relative attachment coefficients were related to the response signal of the electron capture detector, and for the known identified organic chlorides in crude oil and its distillates, their relative attachment coefficients were in the range of 10−10 000, while 5-chloro-2-methylaniline and 3chloro-2-methylaniline have relative attachment coefficients of Received: September 29, 2016 Revised: December 16, 2016 Published: December 16, 2016 374

DOI: 10.1021/acs.energyfuels.6b02527 Energy Fuels 2017, 31, 374−378

Article

Energy & Fuels Table 1. Parameters of the AB-1 Column column name

composition

polarity

temperature limit (°C)

manufacturer

AB-1

100% dimethylpolysiloxane

nonpolar

from −60 to 325

Abel Industries, Ltd.

only approximately 1.0,13 which makes the identification of organic chlorides in SL crude oil difficult. In this work, the distillates of SL crude oil were obtained by means of an atmospheric distillation instrument. Then, the chloride distribution of SL crude oil was determined by measuring the contents of inorganic and organic chlorides in each distillate. Qualitative and quantitative analyses of organochlorine compounds in light distillates, such as naphtha, kerosene, and light diesel, were carried out by gas chromatography equipped with an electron capture detector (GC−ECD).13,14

3. RESULTS AND DISCUSSION 3.1. Properties of SL Crude Oil. As seen in Table 2, the density of SL crude oil at 20 °C was 943.6 kg/m3, which was Table 2. Properties of SL Crude Oil

2. EXPERIMENTAL SECTION 2.1. SL Crude Oil Properties. The SL crude oil sample was obtained from the Shengli oilfield located in east China. The properties of the SL crude oil sample, such as the density, kinematic viscosity, solidification point, carbon residue content, water content, ash content, total acid number (TAN), total chlorine content, and inorganic chlorine content, were determined according to the corresponding Chinese national standards and China petroleum and natural gas industry standards. 2.2. Atmospheric Distillation of SL Crude Oil. Five types of distillates were obtained by atmospheric distillation, i.e., naphtha, kerosene, light diesel, heavy diesel, and atmospheric residue from the SL crude oil. 2.3. Measurement Method for Chloride. The total chlorine contents of crude oil and its distillates were determined according to GB/T 18612-2011 using a KY-200 microcoulomb titrameter (Keyuan Electron & Instrument Co., Ltd., China). The inorganic chlorine contents of crude oil and its distillates were identified according to SY/ T 0536-94 using a RPP-200C salt content determinator (Zhonghuan Analysis Co., Ltd., China). Consequently, the organic chloride contents of crude oil and its distillates were obtained by the following equation:

standard GB/T 2540-81(88) GB/T 265-88 SY/T 0541-2009 GB/T 268-87 GB/T508-85(91) GB/T 260-77(88) GB/T 264-83(91) GB/T 18612-2011 SY/T 0536-94

Table 3. Yields of Distillates from SL Crude Oil (1)

2.4. Qualitative and Quantitative Analyses of Organic Chloride by GC−ECD. The morphologies of organochlorine compounds in light distillates of SL crude oil were identified by GC−ECD (Beifen SP3400). The contents of organic chlorides identified from naphtha, kerosene, and light diesel were calculated using the following equation:10

ci = csAi /A s

data 943.6 275.19 7 7.5 0.55 0.10 1.83 195.11 6.43 188.68

higher than 930 kg/m3.15 Therefore, SL crude oil could be catalogued as heavy crude oil. The ash content of SL crude oil was up to 0.55 wt %, which meant that a large amount of solid impurities existed in the SL crude oil. The total chlorine content (195.11 mg/L) included the inorganic chlorine content (6.43 mg/L); thus, the organic chlorine content of the crude oil was 188.68 mg/L. The organic chlorine content of the crude oil was extremely high, even much higher than the relative standard of Chinese refineries (less than 1.0 mg/L). Currently, more than 2 × 106 tons of the high chlorine content crude oil is still stored in tanks without being processed. 3.2. Atmospheric Distillation Data. The data regarding the distillation ranges and yields of different distillates are listed in Table 3. The SL crude oil was processed throughout the

organic chloride content = total chlorine content − inorganic chloride content

item density at 20 °C (kg/m3) kinematic viscosity at 50 °C (mm2/s) solidification point (°C) carbon residue content (wt %) ash content (wt %) water content (wt %) total acid number (TAN) (mg of KOH/g) total chlorine content (mg/L) inorganic chlorine content (mg/L) organic chlorine content (mg/L)

(2)

where Ci is the concentration of the corresponding organic chloride in the distillate (mg/L), Cs is the concentration of the authentic standard (mg/L), Ai is the chromatographic peak area of the corresponding organic chloride in the distillate (mV), and As is the chromatographic peak area of the authentic standard (mV). A 1 μL aliquot of the liquid sample was successfully injected into the GC−ECD with a manual injector, and organic chlorides were separated by a 30 m × 0.32 mm (internal diameter) × 0.25 μm (film thickness) AB-1 column. Some detailed information about the AB-1 column is listed in Table 1. The nitrogen carrier gas was maintained at a constant flow of 3.0 mL/min. The temperature program began at 40 °C (held for 8 min), was subsequently increased to 100 °C at a rate of 7 °C/min (held for 2 min), then was increased to 120 °C at 10 °C/min (held for 2 min), and finally was increased to 300 °C at 7 °C/min (held for 2 min). The split-flow ratio was 80:1, and the column pressure was 2.5 MPa. The operating temperatures of the injector and ECD detector were 300 and 320 °C, respectively.

distillate of crude oil

distillation range (°C)

yield of distillate (vol %)

naphtha kerosene light diesel heavy diesel atmospheric residue total loss

118−180 180−230 230−300 300−350 >350

2.76 3.31 12.83 22.20 54.20 95.30 4.70

atmospheric distillation instrument, and the total volumetric yield of distillate was 95.30%, with a loss of 4.70%. The volumetric yields of the naphtha (118−180 °C), kerosene (180−230 °C), light diesel (230−300 °C), and heavy diesel (300−350 °C) fractions were 2.76, 3.31, 12.83, and 22.20%, respectively, while the proportion of atmospheric residue with a boiling point greater than 350 °C reached up to 54.20%. 3.3. Distribution of Chloride in SL Crude Oil. The total chlorine, inorganic chlorine, and organic chlorine contents of all distillates were determined using the method described above. The data in Table 4 present the distribution of chloride in SL crude oil. The inorganic chlorine contents of distillates with boiling points in the range of 118−350 °C were extremely low, and inorganic chlorides were mainly concentrated in the 375

DOI: 10.1021/acs.energyfuels.6b02527 Energy Fuels 2017, 31, 374−378

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Energy & Fuels Table 4. Distribution of Chloride in SL Crude Oil distillate of crude oil naphtha kerosene light diesel heavy diesel atmospheric residue chlorine balance of distillates

distillation range (°C)

total chlorine content (mg/L)

inorganic chlorine content (mg/L)

organic chlorine content (mg/L)

118−180 180−230 230−300 300−350 >350

302.93 729.50 837.02 124.31 43.72

0 0.05 0.12 0.13 11.21

302.93 729.45 836.90 124.18 32.51

191.19

6.12

185.07

Figure 1. Chromatograms of authentic standards: (a) carbon tetrachloride, (b) trichloroethylene, (c) tetrachloroethylene, (d) 1,2,3-trichloropropene, (e) 3-chloro-2-methylaniline, (f) 5-chloro-2methylaniline, and (g) 2,6-dichloro-3-methylaniline.

atmospheric residue; thus, the inorganic chlorine contents of distillates increased with an increase in the boiling point range. Moreover, organic chlorides could be found in each distillate of SL crude oil, especially for light diesel, in which the content of organic chloride was as high as 837.02 mg/L, which is much higher than for the other distillates. Meanwhile, the atmospheric residue contained the lowest organic chlorine content, as it was only 32.51 mg/L. Consequently, organic chloride in the distillates of SL crude oil exhibited a dropshaped regular distribution pattern, indicating that organic chlorides were mainly concentrated in the naphtha, kerosene, light diesel, and heavy diesel, in which the organic chlorine accounted for 90.48% of the total organic chlorine of crude oil. The above analysis indicated that artificially added high-boilingpoint organic chlorides rather than inherent organic chlorides were responsible for the dominance of organic chlorides in SL crude oil. Meanwhile, the organic chlorides in the atmospheric residue could be regarded as naturally occurring. On the basis of the chlorine balance of the distillates, the total chlorine, inorganic chlorine, and organic chlorine contents of SL crude oil were 191.19, 6.12, and 185.07 mg/L, respectively, which was slightly less than the data of the corresponding chlorines listed in Table 2. This difference may come from the experimental error and the evaporation of low-boiling-point organic chlorides during the process of atmospheric distillation. 3.4. Authentic Standards of Organic Chlorides. According to the GC operating conditions mentioned in section 2.4, authentic standard solutions that contained dissolved carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,2,3-trichloropropene, 3-chloro-2-methylaniline, 5chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline in nhexane were injected into GC. The authentic standard chromatograms are displayed in Figure 1. The retention times, peak areas, and organic chloride contents of the corresponding authentic standards are listed in Table 5. 3.5. Qualitative and Quantitative Analyses of Light Distillates. According to the GC operating conditions mentioned in section 2.4, naphtha, kerosene, and light diesel samples were injected into GC. The gas chromatograms of the three light distillates are displayed in Figures 2−4. Qualitative identification of different organic chlorides in the light distillates was carried out by GC−ECD via comparison to the retention times of the authentic standards listed in Table 5. As seen in Figure 2, seven types of organic chlorides were identified from naphtha, i.e., carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,2,3-trichloropropene, 3-chloro2-methylaniline, 5-chloro-2-methylaniline, and 2,6-dichloro-3methylaniline. Figure 3 displays that four types of organic chlorides, including trichloroethylene, 3-chloro-2-methylaniline,

5-chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline, existed in kerosene. Moreover, trichloroethylene, tetrachloroethylene, 3-chloro-2-methylaniline, 5-chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline were found to exist in light diesel, as seen in Figure 4. In addition, the chromatographic peaks in the GC−ECD spectra of the light distillates exhibited similar appearances, where trichloroethylene, 3-chloro-2-methylaniline, 5-chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline were identified in the three types of light distillates. A similar distribution of organic chlorides in the distillates of YS crude oil was also reported by Wu and co-workers.10 A quantitative analytical method was established for the organic chlorides in the light distillates of SL crude oil using the external standard method. According to the peak areas of the authentic standards with specified concentrations, the contents of organic chlorides in the three types of light distillates were calculated by eq 2 and listed in Tables 6−8. As seen in Tables 6−8, the organic chlorine contents of the three light distillates were measured by GC−ECD as 223.71, 701.20, and 809.56 mg/L, respectively, which were smaller than the data obtained via the subtraction method, mentioned in section 2.3. These results indicated that most organic chlorides in light distillates had already been identified, while several trace organic chlorides could not be detected as a result of the lack of authentic standards, especially those with high boiling points. A large amount of 5-chloro-2-methylaniline existed in the light distillates, which accounted for 78.77% of the organic chloride content in naphtha, 82.84% in kerosene, and 80.71% in light diesel.

4. CONCLUSION (1) SL crude oil is a heavy crude oil with an extremely high content of chlorine. Its total chlorine content, organic chlorine content, and inorganic chlorine content were 195.11, 188.68, and 6.43 mg/L, respectively. The volumetric yield of light distillates with boiling points less than 350 °C was only 41.1%, and the proportion of atmospheric residue (bp > 350 °C) was as high as 54.20%. (2) Organic chlorides existed in all of the distillates of SL crude oil. The organic chlorides were mainly enriched in kerosene and light diesel, with organic chlorine contents of 729.50 and 837.02 mg/L, respectively. The distribution regularity of organic chlorides in SL crude oil was closely related to the occurrence state of organic chlorides in SL crude oil. (3) According to qualitative and quantitative analyses via GC−ECD, similar distributions of organic 376

DOI: 10.1021/acs.energyfuels.6b02527 Energy Fuels 2017, 31, 374−378

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Energy & Fuels Table 5. Concentrations, Retention Times, and Peak Areas of Organic Chloride Standard Solutions number

purity grade

retention time (min)

authentic standards

peak area (mV)

organic chlorine content (mg/L)

a b c d e f g

AR AR AR AR AR AR AR

1.192 1.482 2.829 5.922 19.643 19.820 20.462

carbon tetrachloride trichloroethylene tetrachloroethylene 1,2,3-trichloropropene 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2,6-dichloro-3-methylaniline

3508975 1408937 5516299 8778945 1136562 1784197 781166

28.83 12.38 10.60 33.14 186.98 300.18 93.45

Table 6. Types, Retention Times, Peak Areas, and Contents of Organic Chlorides in Naphtha

number a b c d e f g total

Figure 2. Gas chromatogram of naphtha.

retention time (min)

organic chloride

peak area (mV)

1.134 1.482 2.897 5.928 19.612 19.866 20.493

carbon tetrachloride trichloroethylene tetrachloroethylene 1,2,3-trichloropropene 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2,6-dichloro-3-methylaniline

35281 140432 66983 218944 164049 1047340 151022

organic chlorine content (mg/L) 0.29 1.19 0.13 0.83 26.99 176.21 18.07 223.71

Table 7. Types, Retention Times, Peak Areas, and Contents of Organic Chlorides in Kerosene

number b e f g total

retention time (min)

organic chloride

peak area (mV)

1.501 19.650 19.907 20.497

trichloroethylene 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2,6-dichloro-3-methylaniline

512822 358947 3452563 474566

organic chlorine content (mg/L) 4.51 59.05 580.87 56.77 701.20

Table 8. Types, Retention Times, Peak Areas, and Contents of Organic Chlorides in Light Diesel

Figure 3. Gas chromatogram of kerosene.

number b c e f g total

retention time (min)

organic chloride

peak area (mV)

1.499 2.884 19.619 19.883 20.483

trichloroethylene tetrachloroethylene 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2,6-dichloro-3-methylaniline

207770 146589 315583 3883790 853578

organic chlorine content (mg/L) 1.83 0.28 51.92 653.42 102.11 809.56

of 176.21, 580.87, and 653.42 mg/L in naphtha, kerosene, and light diesel, respectively.

Figure 4. Gas chromatogram of light diesel.

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chlorides in the light distillates of SL crude oil were revealed. Trichloroethylene, 3-chloro-2-methylaniline, 5-chloro-2-methylaniline, and 2,6-dichloro-3-methylaniline were all identified from naphtha, kerosene, and light diesel. The quantitative analysis results indicated that most of the organic chlorides in light distillates had already been identified, in which the dominant species was 5-chloro-2-methylaniline, with contents

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.6b02527. Some information pertaining to the organic chloride authentic standards (Table S-1) (PDF) 377

DOI: 10.1021/acs.energyfuels.6b02527 Energy Fuels 2017, 31, 374−378

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Energy & Fuels

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AUTHOR INFORMATION

Corresponding Author

*Telephone: +86-10-8973-9029. Fax: +86-10-8970-2776. Email: [email protected]. ORCID

Jianhua Zhu: 0000-0002-0551-3521 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the 21206194 Project of the National Natural Science Foundation of China. REFERENCES

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DOI: 10.1021/acs.energyfuels.6b02527 Energy Fuels 2017, 31, 374−378