Comprehensive Characterization of Petroleum Acids by Distillation

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Comprehensive Characterization of Petroleum Acids by Distillation, SPE Separation and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Amy Clingenpeel, Thomas Fredriksen, Kuangnan Qian, and Michael R. Harper Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b02085 • Publication Date (Web): 21 Aug 2018 Downloaded from http://pubs.acs.org on August 21, 2018

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Comprehensive Characterization of Petroleum Acids by Distillation, SPE Separation and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Amy C. Clingenpeel*, Thomas R. Fredriksen, Kuangnan Qian, Michael R. Harper ExxonMobil Research and Engineering Company, Annandale, New Jersey 08801, United States Abstract Crude acids or petroleum acids are considered to be one of the prime contributors to corrosion, emulsion, and fouling issues across upstream, downstream, and chemical operations. Thus, the composition of crude acids has been extensively studied in the last several decades. To achieve molecular level characterization, mass spectrometry is typically applied. However, one of the challenges in mass spectrometry characterization is that dynamic range of the technique can severely limit the compositions observed. Here, we employ multiple separations before analyzing crude oil acid fractions to overcome this limitation. First, a whole crude (WC) oil was distilled into boiling point fractions including vacuum gas oil (VGO) and vacuum residue (VR). Acids were then collectively isolated from the VGO and VR fractions as well as the starting WC using a solid phase extraction (SPE) method. Isolated acids were also further separated by molecular weight (MW) using a similar SPE technique. The acid fractions were then characterized by negative-ion (-) electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry

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(FT-ICR MS). This combined analytical approach produced a comprehensive acid composition of the crude oil, and a more accurate distribution of the acids as a function of boiling point. Comparison of the WC acid fractions to the VGO and VR acid fractions reveals that direct analysis of the WC fractions does not cover the full composition as exhibited through the combined analysis of the VGO and VR fractions. Thus, further fractionation of the crude oil, such as through distillation, aids in overcoming dynamic range limitations associated with FT-ICR MS. Introduction Crude acids are one important class of compounds in petroleum raw materials and products. They are considered to be prime contributors to corrosion problems across upstream, downstream, and chemical operations.1-4 Petroleum acids are found predominantly in immature, biodegraded, heavy crudes. The concentrations and compositions of the acids are related to petroleum formation and migration.5,6 Acids in petroleum products are typically formed via oxidation during usage (e.g. engine oil degradation) and are one compositional indicator of product stability and quality.7 In addition, many acid components are associated with emulsion and fouling issues in oil production, transportation, and de-salting operations.8-11 For these reasons, petroleum acid levels are frequently monitored in terms of total acid number (TAN) measurements. Crude oils are considered acidic if their TAN exceeds 0.5 mg KOH/g by non-aqueous titration. In many cases, the distribution of TAN as a function of boiling point is monitored to account for liquid-phase corrosion at corresponding processing temperatures.12 TAN is also used to monitor lube oil degradation. Compositions of crude acids have been extensively studied in the last several decades. Because of their lower concentrations and high polarities, these molecules are typically isolated, by a variety of analytical techniques, from the hydrocarbon matrix before characterization. To achieve molecular level characterization, gas chromatography and mass spectrometry are typically applied.


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For example, exhaustive extraction and selective reduction to parent hydrocarbons has been combined with high-resolution MS to identify steroid carboxylic acids.13-16 Early research explored using negative-ion chemical ionization mass spectrometry to generate ring type and carbon number distributions. A range of acid molecules with 0−6 naphthenic rings and carbon numbers of 10−50 were reported.15 Starting in the early 2000’s, ESI combined with ultrahigh resolution FT-ICR MS was explored for detailed analysis of heteroatom-containing compositions including crude acids.17-20 A great deal of compositional information was revealed. For example, in addition to naphthenic acids, ESI FT-ICR MS analyses showed the presence of aromatic and hetero-aromatic acids (N-, S-, NOx-, and SOx-containing hydrocarbons) with double bond equivalences up to 40 and carbon numbers up to 100.21-28 One of the challenges in mass spectrometry characterization is that dynamic range of the technique can severely limit the compositions observed. This is especially true in ultra-high resolution mass spectrometry where a large number of molecules exist in a petroleum sample (e.g. VR). Advances in mass spectrometry, such as, the increase of magnetic field strength29,30 and improvements in ICR cell design31 can help to increase the dynamic range. Alternatively, dynamic range can also be greatly improved by the so called “divide and conquer”32-34 approach (e.g. distillation, chromatographic separation, de-asphalting, solvent extraction, etc.). Recently, a SPE method was reported by Rowland et al. to extract and separate petroleum acids by MW.35A significant increase in compositional coverage was observed when the extracted fractions were further characterized by (-) ESI FT-ICR MS. In this work, we distilled a heavy, high TAN (~4 mg KOH/g) crude oil to generate VGO and VR fractions. To produce a comprehensive acid composition of the crude oil, acids were collectively isolated from the VGO and VR fractions as TAN data suggested that organic acids were primarily


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concentrated in these two fractions. Acids were also collectively isolated from the starting WC oil for comparison. Additionally, acids were further separated by MW using an SPE method similar to that described in Rowland’s work.8,35 The acid fractions were then characterized by either (-) ESI FT-ICR MS or by positive-ion (+) atmospheric pressure photoionization (APPI) FT-ICR MS. (-) ESI FT-ICR MS preferentially ionizes carboxylic acids, and therefore, was a logical choice for characterizing all acid fractions. (+) APPI FT-ICR MS was used to determine if condensed aromatic rings were present in the latest eluting fraction since it did not ionize by (-) ESI FT-ICR MS. This combined analytical approach produced a more accurate distribution of acids as a function of boiling point. Experimental Materials. All materials were used as received. High performance liquid chromatography (HPLC) grade dichloromethane (DCM) and water (H2O) were purchased from J.T. Baker (Phillipsburg, NJ). HPLC grade toluene was purchased from Honeywell (Richmond, VA). Liquid chromatography-mass spectrometry (LC-MS) grade methanol (MeOH) was purchased from EMD Millipore (Mahopac, NY). Isolation and fractionation of acids was performed on Agilent Bond Elut NH2 2 g SPE cartridges, which are described in further detail below. Formic acid (FA), purchased from Sigma-Aldrich (MS grade, ~98%, St. Louis, MO), was used to elute acids from the SPE cartridge. Ammonium hydroxide (Honeywell, 28% NH3 in H2O, ≥99.99%) was used to aid in deprotonation for (-) ESI FT-ICR MS analyses. Acid Isolation and Fractionation. Two separations utilizing aminopropyl silica (APS) SPE cartridges were performed (Figure 1). First, acids were collectively isolated from the WC, VGO, and VR samples following a previously described method.35 In brief, the SPE cartridges were conditioned with ~12 mL of DCM. Approximately 100 mg of each sample was dissolved in 1 mL


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of DCM and loaded drop wise onto separate SPE cartridges. The samples were allowed to equilibrate with the stationary phase for ~15 minutes. After equilibration, the non-acids were collected by washing with ~12 mL DCM and ~12 mL 50:50 (v:v) DCM:MeOH. Acids were then collected by washing with ~12 mL 50:50 DCM:MeOH with 5% FA. These acids will be referred to as single-pass total acid fractions.

Single-Pass Total Acid Isolation APS Conditioned with DCM

Non-Acids

Non-Acids

Acids

(100%) DCM

(50:50) DCM/MeOH

(50:50:5) DCM/MeOH/FA

MAPS Fractionation APS Conditioned with DCM

MA 1

MA 2

MA 7

MA 8

(70:30:5) MeOH/H2O/FA

(80:20:5) MeOH/H2O/FA



MN 1

MN 4

MA 3

MA 6

(100%) DCM

(70:30) MeOH/H2O

(90:10:5) MeOH/H2O/FA


MN 2

MN 3

MA 4

MA 5

(50:50) DCM/MeOH

(100%) MeOH

(100:5) MeOH/FA


Figure 1. Separation schemes for single-pass total acid isolation (top) and MAPS fraction of acids (bottom). Acids were also isolated and further fractionated by MW from the WC, VGO, and VR samples using APS SPE cartridges according to the modified aminopropyl silica (MAPS) extraction method (Figure 1).8,35 First, each SPE cartridge was conditioned with ~12 mL of DCM. Approximately 500 mg of each sample was dissolved in 1 mL of DCM. After conditioning, each sample was loaded drop wise onto separate SPE cartridges. Each sample was allowed to equilibrate with the stationary phase for ~15 minutes. After equilibrating, MAPS non-acids (MN) were collected from each sample by washing with ~12 mL of DCM and ~12 mL of 50:50 DCM:MeOH. The mobile phase was then switched to a reverse phase composition by washing with ~12 mL of


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MeOH and ~12 mL of 70:30 MeOH:H2O. FA was then introduced to the mobile phase to collect the acid fractions. A total of 8 different acid fractions were collected from each sample following the solvent scheme shown in Figure 1. FT-ICR MS Sample Preparation. All samples were first dissolved in toluene, and in the case of electrospray analysis, further diluted in methanol to enable stable spray. The collectively isolated acid fractions as well as MAPS acid (MA) 1-7 fractions from each sample were blended to approximately 5-200 µg/mL, adjusted for adequate response, in a 3:17 ratio of toluene to methanol. Ammonium hydroxide solution was added to facilitate deprotonation at approximately 1% of the total solution for (-) ESI analyses. The WC and VR MA8 fractions were blended in toluene, and analyzed as-is via (+) APPI. Instrumentation. All experiments were performed on a 15T Bruker solariX FT-ICR MS using the included instrument control software, ftmsControl (Bruker Daltonics, version 2.1.0). Ion accumulation time was set between 0.010 and 0.250 seconds, and adjusted for response. Collision cell RF frequency and amplitude were 2 MHz and 1000 Vpp, respectively. Sign of the following voltages were dependent on positive ion or negative ion ionization mode: transfer exit voltage was (+/-) 20.0 V, analyzer entrance was (+/-) 10.0 V, side kick and side kick offset were 0 V and (+/-) 1.5 V, respectively, and front and back trap plates were both set to (+/-) 1.9 V. A total of 200 scans were co-added in all analyses. Data acquisition size was 8 M. Further conditions are outlined below according to the ionization method employed. APPI Desolvation and dry gas temperatures were set to 420 °C and 200 °C, respectively. Nebulizer gas flow rate was 1.5 bar. Dry gas flow was 4.0 L/min. Capillary voltage was 2600 V. End plate offset


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was -500 V. Capillary exit was 220 V. The time of flight was 1.000 milliseconds (ms). The detected mass range was 250-3000 m/z. The resolving power (RP) at 400 m/z was ≥ 1,400,000 and the average root mean square (RMS) error across all experiments was 48 parts-per-billion (ppb). ESI Dry gas temperature and flow were set to 200 °C and 5.0 L/min, respectively. Nebulizer gas flow was 1.5 bar. Capillary voltage was 3600 V. End plate offset was -500 V. Capillary exit was -190 V. Time of flight was either 0.850 or 1.400 ms depending on the sample analyzed, but was kept constant across sample sets (i.e. all MA 1 fractions, etc.). The detected mass range was either 1502000 m/z or 250-3000 m/z depending on the sample, but again was constant across sample sets. The RP at 400 m/z was ≥ 900,000 and the RMS error across all experiments was 48 ppb. Data Analysis. The raw mass spectral data was calibrated using Bruker Compass DataAnalysis 4.5 software, as previously described.36 Data was internally calibrated using a homologous series, then exported to a table of mass and intensity. Background and noise peaks were removed, as well as those that do not fall into a Kendrick mass defect series. This “cleaned” and adjusted mass and intensity table was further exported to PetroOrg S-10.2 software for formula assignment and then to internal software to visualize acid compositions. Results and Discussions Distribution of Acids. Approximately 90-96% of material loaded from each sample eluted in the non-acid fractions. A distribution of acids collected from each sample is shown in Table 1. Based on the work by Rowland et al., the expected error in mass recovery is expected to be ≤ 1 weight percent across all fractions. For the WC and VR, acids are concentrated in the higher MW MA fractions (MA 6-8). The opposite is observed for the VGO, where acids are most concentrated in


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the lower MW MA fractions (MA 1-3). This particular crude contains ~44 wt% VR (1050 °F+), ~40 wt% VGO (650-1050 °F) and ~16% 650 °F-. The WC acid fraction yields trend more closely to that of VR (versus VGO). The acid fraction yields of the WC do not balance well with respect to the combination of VGO and VR. While this is expected due to the limited capacity of the SPE cartridge, it is also possible that the MAPS separation is affected by petroleum matrices. Table 1. Distribution of acids isolated from each sample by the MAPS fractionation technique. The WC MA yields appear to trend more closely to the VR than the VGO. WC Fraction WC NonAcids

VGO Mass (mg)

Weight Percent (%)

Fraction

VR Mass (mg)

Weight Percent (%)

Fraction

Mass (mg)

Weight Percent (%)

416.55

94.98

VGO Non-Acids

487.88

96.6

VR Non-Acids

366.52

92.35

WC MA 1

1.62

0.37

VGO MA 1

5.97

1.18

VR MA 1

1.84

0.47

WC MA 2

0.44

0.10

VGO MA 2

3.19

0.63

VR MA 2

1.26

0.32

WC MA 3

1.61

0.37

VGO MA 3

2.51

0.50

VR MA 3

1.92

0.49

WC MA 4

2.36

0.54

VGO MA 4

0.52

0.10

VR MA 4

3.04

0.77

WC MA 5

1.17

0.27

VGO MA 5

0.15

0.03

VR MA 5

1.19

0.30

WC MA 6

1.59

0.36

VGO MA 6

0.54

0.10

VR MA 6

1.92

0.49

WC MA 7

3.61

0.82

VGO MA 7

0.43

0.09

VR MA 7

3.78

0.96

WC MA 8

6.74

1.54

VGO MA 8

0.67

0.13

VR MA 8

16.57

4.19

Recovery

99.37%

Recovery

99.36%

Recovery

100.56%

Comprehensive acid analyses were performed by analyzing each acid fraction by FT-ICR MS. Single-pass total acid fractions as well as MA fractions 1-7 from each sample were characterized by (-) ESI FT-ICR MS. When MA 8 fractions were characterized by (-) ESI FT-ICR MS, no signal was observed, even at increased concentrations (up to 500 µg/mL). Since the VGO did not contain a significant amount of material in the MA 8 fraction while both the WC and VR did, it was hypothesized that the MA 8 fractions may contain highly condensed aromatic, asphaltene-like material (n-heptane insoluble). Therefore, these MA 8 fractions were characterized by (+) APPI FT-ICR MS to facilitate ionization of condensed aromatic hydrocarbon species. No further analyses were performed on the MA 8 VGO fraction since there was not an appreciable amount of material left after attempted (-) ESI analyses, and due to the fact that (+) APPI analyses required


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increased concentrations (up to 200 µg/mL). Composition of the single-pass total acids and MA 1-7 fractions from each different sample are discussed in further detail below while the composition of the MA 8 fraction from the WC and VR is discussed in the Supplemental Information. Composition of Acids Vacuum Gas Oil MW distributions of the single-pass total acid fraction as well as MA 1-7 fractions from the VGO are shown in Figure 2. The FT-ICR MS conditions were tuned to capture the breadth of the mass spectrum for the single-pass total acid fraction. The distribution of the single-pass total acid fraction is observed to range from ~250 m/z to ~640 m/z. However, fractionation of the acids by the MAPS separation reveals slightly broader acid distributions with high molecular weight species extending to ~800 m/z. These results clearly demonstrate the benefit of the MAPS separation in expanding the dynamic range of FT-ICR MS analyses. Even though the MAPS separation extends the dynamic range, the VGO sample exhibits a sharp cut-off in MW at MA 4. Beyond MA 4, the MW range does not significantly change. This abrupt cut-off in MW range can easily be explained by the distillation as the VGO has an upper boiling range limit of ~1050 °F. Therefore, higher MW species (beyond ~800 m/z) are not present in this fraction.37 The heteroatom compound class distributions for the VGO MA fractions is displayed in Figure 3. It is important to note that acids containing at least 2 oxygens were observed in every fraction from every sample. Thus, the separation is specific for carboxylic acid-containing species. Two types of acids (containing 2O and 4O) are observed in the VGO above 0.5% relative abundance. 2O species are mono-acids (i.e. carboxylic acids), while 4O is believed to be mostly di-acids.


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Compositional changes are evident from MA1 to MA4, where 4O is decreasing and 2O is increasing. From MA5 to MA7, the compositions are relatively constant.

Figure 2. MW distributions of the single-pass total acid fraction as well as MAPS acid fractions isolated from the VGO. MAPS fractionation clearly extends the dynamic range. Figure 4 (top) shows the Z-distribution of the 2O compound classes for MA 1, 3, 5 and 7 fractions. These fractions were chosen to highlight the compositional differences across all MA fractions. Figure 4 (bottom) displays the Z-class vs. MW distributions for all 2O compounds in the VGO MA fractions where Z-class is generally referred to as hydrogen deficiency in the molecular formula CnH2n+zO0. MA 1 shows the most diverse composition ranging from saturated acids (Z=0) to polyaromatic acids (Z=-26) with the most abundant acid type being two naphthenic rings (Z=4). As MA fractions increase, the acid cores become more saturated and less aromatic. The abundance of saturated and 1-ring naphthenic acids increases substantially. The observed Z-class distribution remains consistent for MA 3-7.


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Figure 3. Heteroatom class distribution for MAPS acid fractions isolated from the VGO. Twoand four-oxygen containing species, mono- and di-acids respectively, are identified. VGO MA 1 VGO MA 3 VGO MA 5 VGO MA 7

25 Total Intensity

(-) ESI

VGO 2O Z-Class Distribution

30

Mon-arom. Acids + 4-6 Ring Naph Acids

Di-arom. Acids

Tri-arom. Acids

1-3 ring Naph. Acids

Fatty Acids

20

15

10

5 0 -32

-30

-25

VGO MA 1

-20

VGO MA 2

-15 Z-Class

VGO MA 3

VGO MA 4

-10

VGO MA 5

-5

VGO MA 6

0

VGO MA 7

Max

2

Z Class

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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-15

-32 175

562.5

950 175

562.5

950 175

562.5

950 175

562.5

MW

950 175

562.5

950 175

562.5

950 175

562.5

950

Zero

Figure 4. Z-class distribution (top) and Z-class vs. molecular weight plots (bottom) for 2O species in the MAPS acids fractions isolated from the VGO. The most diversity in Z-class is observed in the most polar MA fraction, MA 1.


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Vacuum Residue The mass distributions for the single-pass total acid fraction as well as MA 1-7 fractions from the VR are shown in Figure 5. The FT-ICR MS conditions were tuned to capture the breadth of the mass spectrum for the single-pass total acid fraction. The single-pass total acid fraction extends

Figure 5. MW distributions of the single-pass total acid fraction as well as MAPS acids fractions isolated from the VR. MAPS fractionation extends the dynamic range as more species are observed at lower MW. from ~400 m/z to ~1200 m/z and is centered at ~700 m/z. While fractionation by the MAPS separation does not extend the upper mass limit, it is apparent that it does indeed extend the dynamic range of the analysis as more information is captured at low m/z. The conditions used to capture the most information in the single-pass total acid fraction highlight the high MW species. Yet, low MW compositional information is lost due to dynamic range limitations. Fractionation by the MAPS separation reveals that low MW species are present in the VR starting at ~275 m/z. With each successive MAPS fraction, the distribution shifts to higher MW. This continues through


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MA 7 where the distribution extends to ~1200 m/z as the VR does not have an upper boiling point limit like the VGO. VR Heteroatom Classes

(-) ESI

100 VR MA 1 VR MA 2 VR MA 3 VR MA 4 VR MA 5 VR MA 6 VR MA 7

80

% 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 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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60

40

20

0 O2

O3

O4

N1O2

Figure 6. Heteroatom class distribution for MAPS acid fractions isolated from the VR. More diversity is observed in the VR compared to the VGO. Figure 6 reveals that the heteroatom compound class distribution of VR MA 1-7 fractions are much more complex than that of the VGO. In addition to 2O and 4O species, a substantial amount of 3O and 1N2O species are observed. Most of the 3O, 4O and 1N2O species are found in MA fractions 1-3, while later eluting MA fractions have a greater relative abundance of 2O species. Figure 7 (top) shows the Z-class distribution of the 2O compound classes for MA1, 3, 5 and 7. These fractions were chosen to highlight the compositional differences across all MA fractions. Figure 7 (bottom) displays the Z-class vs. MW distributions for all 2O compounds in the VR MA fractions. As observed in the VGO fractions, early eluting fractions (MA 1 and 3) display the largest diversity in Z-class. In MA 1, 2O species detected are most abundant in naphthenic acids and 3-ring aromatic acids. The high abundance of these species leads to the bimodal distribution observed in MA1 in Figure 5. 2O species in MA 3 also range from saturated acids (Z=0) to


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polyaromatic acids (Z=-40) while later eluting fractions show a shift to more saturated species, and are most abundant in 2-ring naphthenic acids (Z=-4). The Z-class distribution of acids in MA fractions 5-7 remain fairly consistent while MW increases with the increase of MA fractions.

VR 2O Z-Class Distribution Di-arom. Tri-arom. Tetra+-arom. Acids Acids Acids

25 VR MA 1 VR MA 3 VR MA 5 VR MA 7

22.5 20

(-) ESI Mon-arom. Acids + 4-6 R Naph Acids

1-3 ring Naph. Acids Fatty Acids

Total Intensity

17.5 15 12.5 10 7.5 5 2.5 0 -44

-40

-30

-20

-10

0

Z-Class 2

VR MA 1

VR MA 2

VR MA 3

VR MA 4

VR MA 5

VR MA 6

VR MA 7

Max

-4 -10

Z Class

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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-16 -22 -28 -34 -40 -46 175

750

1325 175

750

1325 175

750

1325 175

750

MW

1325 175

750

1325 175

750

1325 175

750

1325 Zero

Figure 7. Z-class distribution (top) and Z-class vs. molecular weight plots (bottom) for 2O species in the MAPS acids fractions isolated from the VR. The most diversity with Z-class distribution is observed with the most polar MA fractions, MA 1 and 3. Comparison of Acid Compositional Space by Single-Pass Isolation, MAPS Fractionation, and Distillation + MAPS Fractionation. Acids from the WC were also isolated by the same techniques used for the VGO and VR. MW distributions from the single-pass total acid fraction as well as MA 1-7 fractions are shown in the Supplemental Information. Figure 8 displays a comparison of the single-pass total acid fraction from the WC, the combined MAPS separation from the WC (i.e. sum of the 7 MA fractions from the WC based on yields), and the combined distillation + MAPS separation (i.e. sum of the MAPS fractions from the VGO and VR based on


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distillation and fractionation yields). Although the distribution of the single-pass total acid fraction from the WC was tuned to capture the breadth of the information, a significant amount of

Figure 8. Comparison of the single-pass total acid isolation from the WC, MAPS separation of the WC, and Distillation + MAPS separation combined from the VGO and VR for the 2O (top) and 4O (bottom) species. In order to accurately characterize acids in the whole crude, further separation, such as through distillation, is needed. information is missing at high MW when Z-class vs. MW plots are compared to the combined MAPS separation from the WC as well as the combined distillation + MAPS separation. Although the distribution is shifted towards lower MW for the WC single-pass total acid fraction, even the lowest MW contributions, likely from acids in the VGO boiling range, are not accurately represented when acids are collectively isolated and characterized from the WC. While MAPS fractionation of the WC oil does significantly extend the dynamic range of the technique (Figure 8), comparison of the combined MA fractions from the WC to the combined distillation + MAPS separation plot reveals that limitations still exist when MA fractions from the WC are analyzed directly. Although similar MW ranges are observed in each plot, compositional


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differences are apparent in the 2O and 4O classes. Comparison of the 2O species between combined samples reveals that low MW 2O-containing species are not accurately represented WC MA 1

2

Z Class

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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VGO MA 1

VR MA 1

Max

-35

-72 175

390

605

820

1035

1250 175

390

605

820

MW

1035

1250 175

390

605

820

1035

1250 Zero

Figure 9. Comparison of the acid compositional space for MAPS acid fraction 1 from the WC, VGO, and VR. The compositional space of the WC matches well with the VR, but is not representative of contributions from the VGO. when the WC sample is fractionated and characterized. The combined VGO and VR sample has a much higher abundance of low MW 2O-containing species. Further comparison of the lowest MW fraction (MA 1) between the WC, VGO, and VR reveals that the WC compositional space is very similar to the VR (Figure 9). This trend is apparent across all MA fractions for the WC (See Supplemental Information). Even though both VGO and VR acids are present in the WC, the WC composition for the lowest MW acid fraction is not representative of acids found within the VGO and VR boiling ranges due to dynamic range limitations. Thus, in order to represent acids present within a whole crude oil correctly, further separation beyond MAPS fractionation of a whole crude oil is needed.


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Energy & Fuels

Conclusions A comprehensive characterization of petroleum acids via a combination of distillation and molecular weight separation followed by ultra-high resolution FT-ICR MS was demonstrated. Single-pass total acids isolated from the WC, VGO, and VR suffer from dynamic range limitations compared to acids isolated from these fractions by the MAPS separation technique. MAPS fractionation reveals broad distributions of acids in the WC as well as the VGO and VR fractions. The greatest diversity is observed in the most polar MA fractions (MA 1-3) with respect to both heteroatom class and chemical structure. The most polar VGO acids contain both mono- and dicarboxylic acids ranging from saturated acids up to 3-ring aromatic acids while the most polar VR acids contain 3O and 1N2O acids in addition to mono- and di-carboxylic acids. Carboxylic acids in the VR range from saturated acids up to 4+-ring aromatic acids. When MA fractions from the WC are compared to the combined MA fractions from the VGO and VR, the WC MA fractions are biased towards high MW due to dynamic range limitations. Thus, further fractionation, such as through distillation, is necessary in order to extend the dynamic range. ASSOCIATED CONTENT Supporting Information. The following files are available free of charge. Discussion of WC MA Fractions and MA 8 fractions from the WC and VR (PDF) AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]


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Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Acknowledgements The authors would like to thank Mobae Afeworki, Bryan E. Hagee, and Ashley M. Wittrig for helpful discussions and suggestions.

REFERENCES (1)

Meriem-Benziane, M.; Bou-Said, B.; Boudouani, N. J. Pet. Sci. Eng. 2017, 158,

672. (2)

McGarvey, B.; McGarvey, C. E.; Thakkar, B.; Tucker, L.; Spafford, L.

Hydrocarbon Process. 2017, 96, 27. (3)

Jin, P.; Robbins, W.; Bota, G. Energy Fuels 2017, 31, 10222.

(4)

Flego, C.; Galasso, L.; Montanari, L.; Gennaro, M. E. Energy Fuels 2014, 28,

1701. (5)

Jaffe, R.; Albrecht, P.; Oudin, J. L. Geochim. Cosmochim. Acta 1988, 52, 2599.

(6)

Jaffe, R.; Gallardo, M. T. Org. Geochem. 1993, 20, 973.

(7)

Soleimani, M.; Sophocleous, M.; Wang, L.; Atkinson, J.; Hosier, I. L.; Vaughan,

A. S.; Taylor, R. I.; Wood, R. J. K. Sens. Actuators, B 2014, 199, 247. (8)

Clingenpeel, A. C.; Rowland, S. M.; Corilo, Y. E.; Zito, P.; Rodgers, R. P. Energy

Fuels 2017, 31, 5933. (9)

Brocart, B.; Hurtevent, C. J. Dispersion Sci. Technol. 2008, 29, 1496.


Page 18 of 21

Page 19 of 21 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)

Mapolelo, M. M.; Rodgers, R. P.; Yen, A. T.; Debord, J. D.; Asomaning, S.;

Marshall, A. G.; American Chemical Society: 2008, p ACSAICHE. (11)

Mohammed, M. A.; Sorbie, K. S. Colloids Surf., A 2009, 349, 1.

(12)

Qian, K.; Edwards, K. E.; Dechert, G. J.; Jaffe, S. B.; Green, L. A.; Olmstead, W.

N. Anal. Chem. (Washington, DC, U. S.) 2008, 80, 849. (13)

Schmitter, J. M.; Arpino, P.; Guiochon, G. J. Chromatogr. 1978, 167, 149.

(14)

Shen, J. Anal. Chem. 1981, 53, 475.

(15)

Dzidic, I.; Somerville, A. C.; Raia, J. C.; Hart, H. V. Anal. Chem. 1988, 60, 1318.

(16)

Fan, T. P. Energy Fuels 1991, 5, 371.

(17)

Qian, K.; Robbins, W. K.; Hughey, C. A.; Cooper, H. J.; Rodgers, R. P.;

Marshall, A. G. Energy Fuels 2001, 15, 1505. (18)

Barrow, M. P.; McDonnell, L. A.; Feng, X.; Walker, J.; Derrick, P. J. Anal. Chem.

2003, 75, 860. (19)

Hughey, C. A.; Rodgers, R. P.; Marshall, A. G.; Walters, C. C.; Qian, K.;

Mankiewicz, P. Org. Geochem. 2004, 35, 863. (20)

Hughey, C. A.; Galasso, S. A.; Zumberge, J. E. Fuel 2007, 86, 758.

(21)

Rodgers, R. P.; McKenna, A. M.; Juyal, P.; Marshall, A. G. Prepr. - Am. Chem.

Soc., Div. Pet. Chem. 2010, 55, 101. (22)

Shi, Q.; Zhao, S.; Xu, Z.; Chung, K. H.; Zhang, Y.; Xu, C. Energy Fuels 2010,

24, 4005. (23)

Rowland, S. J.; West, C. E.; Scarlett, A. G.; Jones, D. Rapid Commun. Mass

Spectrom. 2011, 25, 1741. (24)

Liao, Y.; Shi, Q.; Hsu, C. S.; Pan, Y.; Zhang, Y. Org. Geochem. 2012, 47, 51.


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

(25)

Lobodin, V. V.; Juyal, P.; McKenna, A. M.; Rodgers, R. P.; Marshall, A. G. Anal.

Chem. (Washington, DC, U. S.) 2013, 85, 7803. (26)

Pan, Y.; Liao, Y.; Shi, Q.; Hsu, C. S. Energy Fuels 2013, 27, 2960.

(27)

Wang, L.; He, C.; Zhang, Y.; Zhao, S.; Chung, K. H.; Xu, C.; Hsu, C. S.; Shi, Q.

Energy Fuels 2013, 27, 4555. (28)

Liu, Y.; Zhang, Q.; Wang, W.; Liu, Z.; Zhu, X.; Tian, S. China Pet. Process.

Petrochem. Technol. 2014, 16, 8. (29)

Weisbrod, C. R.; Kaiser, N. K.; Anderson, L. C.; Blakney, G. T.; Hendrickson, C.

L.; Marshall, A. G.; Syka, J. E. P.; Early, L.; Mullen, C.; Dunyach, J.-J.; English, A. M.; Shabanowitz, J.; Hunt, D. F.; Hendrickson, C. L.; Marshall, A. G.; Hunt, D. F. J Am Soc Mass Spectrom 2017. (30)

Anderson, L. C.; DeHart, C. J.; Kaiser, N. K.; Fellers, R. T.; Smith, D. F.; Greer,

J. B.; LeDuc, R. D.; Blakney, G. T.; Thomas, P. M.; Kelleher, N. L.; Hendrickson, C. L. J. Proteome Res. 2017, 16, 1087. (31)

Zhdanova, E.; Kostyukevich, Y.; Nikolaev, E.; Zhdanova, E.; Kostyukevich, Y.;

Nikolaev, E.; Kostyukevich, Y.; Nikolaev, E.; Kostyukevich, Y.; Nikolaev, E. Eur J Mass Spectrom (Chichester) 2017, 23, 197. (32)

Klein, G.C.; Angström, A.;Rodgers, R.P.; Marshall, A.G. Energy Fuels 2006, 20,

668. (33)

Putman, J.C.; Rowland, S.M.; Podgorski, D.C.; Robbins, W.K.; Rodgers, R.P.

Energy Fuels 2017, 31, 12064. (34) Chacòn-Patiño, M.L.; Rowland, S.M.; Rodgers, R.P. Energy Fuels 2017, 31, 13509.


Page 20 of 21

Page 21 of 21 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

(35)

Rowland, S. M.; Robbins, W. K.; Corilo, Y. E.; Marshall, A. G.; Rodgers, R. P.

Energy Fuels 2014, 28, 5043. (36)

Wittrig, A.M.; Fredriksen, T.R.; Qian, K.; Clingenpeel, A.C.; Harper, M.R.

Energy Fuels 2017, 31, 13338. (37)

Altgelt, K.H.; Boduszynski, M.M. Composition and Analysis of Heavy Petroleum

Fractions, Marcel Dekker, Inc.: New York, 1994.

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Comprehensive Characterization of Petroleum Acids by Distillation

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