Atmospheric Pressure Photoionization Coupled to Fourier Transform

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Atmospheric Pressure Photoionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry to Characterize Asphaltene Deposit Solubility Fractions: Comparison with Bulk Properties Estrella Rogel, and Matthias Witt Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b02565 • Publication Date (Web): 19 Jan 2016 Downloaded from http://pubs.acs.org on January 24, 2016

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Atmospheric Pressure Photoionization Coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry to Characterize Asphaltene Deposit Solubility Fractions: Comparison with Bulk Properties. Estrella Rogel,1,* Matthias Witt,2 1

Chevron Energy Technology Company, Richmond, CA 94801, USA. 2

Bruker Daltonik GmbH, 28359 Bremen, Germany.

* To whom correspondence should be addressed

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ABSTRACT In the present work, a field deposit, their solubility fractions and heptane-precipitated asphaltenes from the crude oil were analyzed using Atmospheric Pressure Photoionization coupled to Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (APPI FT-ICR MS). The main objective was to evaluate if the compositional distribution of the deposit closely match the bulk data as well as the effect of solubility fractionation in the molecular distribution using APPI. Analyses of the solubility fractions reveal a significant larger number of assigned species than a similar analysis of the unfractionated field deposit. However, the increase of assigned species does not seem to provide more information in terms of the compositional distribution or average properties. The field deposit contains more components with low aromaticity as well as more oxygen-containing species than the heptane asphaltenes. In contrast, heptane asphaltenes are enriched in N-containing species. Average values (H/C, density and molecular weight) calculated for the solubility fractions match remarkably well the bulk values for the asphaltene fractions obtained from the deposit. In contrast, errors for the maltene fraction are much larger. This is the result of the preferential ionization of highly aromatic molecules, less abundant on maltenes than in the asphaltene fractions. These results indicate that APPI provides access to a broad range of molecules in asphaltenes that, collectively, can be used to describe bulk properties of the fraction.


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INTRODUCTION Asphaltene deposition is among the most feared problems by oil well operators. It is difficult and costly to remediate and once it starts, it can become a recurrent problem or, even worse, it can make a well unfeasible. It is known that the formation of asphaltene deposits is caused by changes in solubility of the asphaltenes due to temperature and pressure variations as well as comingling production or well treatments. Detailed analyses of asphaltene deposits can provide important clues about their mechanism of formation. For example, asphaltene deposits often contain iron compounds1,2 that can be associated to adsorption phenomena which play a critical role in the deposition process3. Also, it has been reported that asphaltene deposits are enriched in highly aromatic components in comparison to heptane-precipitated asphaltenes obtained in the lab4,5. In agreement with their higher aromaticity, asphaltenes from deposits are less soluble in hydrocarbons than those obtained in the lab from the corresponding crude oil.6 This observation has been interpreted as the result of slow accumulation and deposition of asphaltenic species during the formation of deposits in comparison to the fast precipitation process used in laboratories.4 As in many other tasks related to asphaltenes, detailed deposit characterization is very challenging since thousands of different molecules can be found in these deposits. Ultrahigh resolution mass spectrometry has been increasingly used to analyze the extraordinary complexity of crude oil related materials.7-10 However, because of the wide range of components of diverse nature present in crude oils and similar materials, no single ionization technique can ionize all of the compounds.9 In fact; detection depends on the applied ionization technique and therefore may provide misleading information,11 so caution should be exercised when results are analyzed in absolute terms. On the other hand, this differentiation in results depending on the ionization


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technique means that specific aspects can be studied using different ionization methods. Additionally, there are some techniques that can ionize a large range of different molecules in comparison to others. For instance, APPI (Atmospheric Pressure Photo Ionization) can efficiently ionize polycyclic aromatic compounds whether they show basic, acidic or neutral characteristics10 while ESI (Electrospray Ionization) preferentially ionize polar compounds.11 It has also been reported that APCI (Atmospheric Pressure Chemical Ionization) preferentially ionize polar compounds.11 However, recent studies have been shown that this technique coupled with CS2 can ionize non polar compounds12,13 and it has shown promising results in the analysis of asphaltenes.14 In particular, asphaltene deposits have been analyzed using Atmospheric Pressure Photoionization (APPI)4 and Electrospray Ionization (ESI).4,10,15,16 These studies have revealed significant differences between field asphaltene deposits coming from production facilities and precipitated asphaltenes obtained using different procedures during lab experiments. In particular, it has been found that solvent drop asphaltenes contain higher double bond equivalents (DBE) than asphaltenes obtained from pressure drop experiments.10 Similarly, field deposit asphaltenes contain higher double bond equivalents than solvent drop asphaltenes4. The FT-ICR MS study of deposits has also shown that some asphaltene inhibitors can contribute to asphaltene deposition of certain crude oils.16 The bulk of these studies have been based on the comparison between deposits from different sources under the same ionization conditions. In the present work, we evaluated if results obtained using APPI FT-ICR MS are representative of the bulk behavior and characteristics of the asphaltenes and, in particular, of asphaltene deposits. In a previous study,17 we compared the distribution and average characteristics of the detectable molecules using APPI FT-ICR MS in asphaltenes with experimental bulk data


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obtained using more conventional approaches. Our goal was to evaluate the link between FTICR MS compositional data and macroscopic behavior. In this previous study, it was found that APPI was particularly suitable to look into the molecular information of the most aromatic and, therefore, less soluble molecules in petroleum. As deposits are enriched in these molecules, our main objective is to evaluate if APPI could provide a compositional distribution for deposits that closely match the bulk data. In order to achieve this goal, a series of solubility fractions obtained from a field deposit, heptane extracted asphaltenes from the original crude oil and the original deposit were studied using APPI FT-ICR MS. These materials were previously separated and analyzed using conventional techniques.5 In the present work, we evaluated whether the compositional data of asphaltene deposits obtained by APPI FT-ICR MS for these highly aromatic materials can be used to predict bulk properties. Additionally, the effect of the solubility fractionation in sample characteristics as well as the comparison between deposited asphaltenes and heptane asphaltenes are addressed in this work.


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EXPERIMENTAL SECTION Samples. A field asphaltene deposit and the corresponding crude oil were obtained from an oilfield produced by CO2 flooding. The deposit was separated by solubility according to a procedure described in detail elsewhere.18 The fractionation was performed using an Accelerated Solvent Extractor Dionex 300. A sample of the material was weighed (mass around 5.0 g) and dissolved in 50 mL of dichloromethane. 50 g of PTFE were added to the solution and stirred for 1 h at room temperature. The solvent was removed by heating at 60°C under nitrogen. The PTFE supported sample was placed into a 100 mL stainless steel cell and extracted with a series of solvents/solvent blends. This procedure yielded six fractions: heptane solubles (Maltenes), 15/85 CH2Cl2/n-heptane solubles (Asphaltene Fraction 1), 30/70 CH2Cl2/n-heptane solubles (Asphaltene Fraction 2), CH2Cl2 solubles (Asphaltene Fraction 3), 90/10 CH2Cl2/CH3OH solubles (Asphaltene Fraction 4) and Fraction 5 which is composed of the remaining material and is extracted using a 90/10 CH2Cl2/CH3OH blend at high temperature (120o C). Fraction distribution and standard data have been published for the fractions elsewhere.5 Only maltenes and asphaltene fractions 1 to 3 were analyzed in this study. Asphaltene fractions 4 and 5 were obtained in negligible amounts. Asphaltenes were extracted from the crude oil using a modification of the ASTM D6560 test.19 In this modified version, A 1/20 sample/n-heptane ratio was used, and the blend was filtered at 80 oC. The precipitated material was washed using hot heptane prior to drying and weighing. Molecular weights were determined by size exclusion chromatography (SEC) using a 30 cm x 7.5 mm PLgel mixed E column (Agilent Technologies) recommended for oligomers and


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polymers up to 25,000 g/mol. Solutions of the fractions were prepared in dichloromethane using concentrations of 100 ppm. The solutions were eluted with a 90/10 dichloromethane/methanol blend at a flow rate of 1.0 mL/min. The temperature was kept constant at 25 oC. A HPLC Agilent model 1100 liquid chromatograph equipped with an evaporative light scattering detector Alltech 2000 was used. The molecular weights were calculated based on a calibration that uses porphyrins, dyes and polyaromatics as standards.20 FT-ICR MS Analysis. The samples were analyzed using a solariX XR FT-ICR mass spectrometer (Bruker Daltonik GmbH, Bremen, Germany) equipped with a 12 T refrigerated actively shielded superconducting magnet (Bruker Biospin, Wissembourg, France) and the ParacellTM analyzer cell. Apollo II Dual ESI/MALDI ion source was used. Samples were analyzed using positive ion mode APPI. Earlier studies of the theoretical aspects of APPI as well as experimental data concluded that negative ion APPI cannot be considered as universal as positive ion APPI.21,22 In fact, it has been shown that in a blend of acidic, basic and amphoteric nitrogen containing-compounds negative-ion APPI showed ions only for the acidic compounds, while positive-ion APPI showed ions for all the compounds in the blend.22The transient length of the mass spectrometric measurements was 3.3 seconds. Sine apodization was applied before Fourier transformation and spectra were processed in absorption mode resulting in a resolving power of 1,300,000 at m/z 400. The spectra were externally calibrated with arginine clusters in electrospray ionization in positive ion mode. During the acquisition the mass spectrum was single point calibrated with a known mass (lock mass calibration). The final spectrum was internally calibrated in DataAnalysis 4.2 (Bruker Daltonics) with a known homologous series using quadratic calibration. All RMS mass errors of the internal calibration were below 110 ppb.


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The average RMS mass error of all internal calibrations of the APPI measurements was only 92 ppb. Samples were prepared by diluting them 1:100 in toluene as stock solution. For APPI measurements, the stock solution was diluted 1:200 in 50/50 CH3OH/toluene for final spray solution (50 ppm). This solution was directly injected to the APPI source with a syringe pump at a flow rate of 10 µL/min. The ion accumulation time was 30 ms and 200 single scans were added for final mass spectrum. Internal mass calibration, spectral interpretation and export of mass lists were performed using DataAnalysis 4.2 (Bruker Daltonics). The analysis of the data, including calculation of molecular formulas and relative abundances of compound classes was performed using Composer 1.0.6 (Sierra Analytics). Elemental composition assignment was based on Kendrick mass defect sorting. Maximum mass error of 0.5 ppm and maximum number of heteroatoms of N=3, O=3 and S=3 were allowed for molecular formula calculations. Double-bond-equivalence (DBE) values representing the number of rings plus the number of double bonds in a given molecular formula were calculated using the following equation:15 DBE=c-h/2+n/2+1

(1)

for the elemental formula CcHhNnOoSs.


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RESULTS AND DISCUSSION Peak Assignments and Class Distributions. Figure 1 shows a comparison in the mass spectra obtained for the solubility fractions of the field deposit. The spectra show signals between m/z 200 to 1400 for the extracted fractions. However, a mass shift of the maximum abundances to larger masses from maltenes to asphaltene fraction 3 was observed. The counts of assigned molecular formulas for each of the solubility fractions as well as the common peak assignments are shown in Table 1. Diagonal numbers (bold) represent the total number of peak assignments per sample. This number decreases from maltenes to Fraction 3 indicating a decrease in the complexity of the sample. This can indicate that the fraction has become progressively less complex as the solubility in hydrocarbons decreases from maltenes to asphaltene fraction 3. This is the result of the sequential fractionation of the deposit with solvents of increasingly polar character. The rest of the numbers in Table 1 represent the number of common peaks shared by each sample with each other. For instance, maltenes and fraction 1 share 8126 common peaks while maltenes and fraction 3 share 5654. These values indicate a significant overlapping in terms of the composition among the fractions. In fact, calculations show that the common peaks represent between 50 to 80 % of each fraction. This finding is not unexpected. More traditional techniques also indicate a significant overlapping in solubility properties for the asphaltene solubility fractions.23 Table 1 also shows that the number of common peaks decreases as the fractions are farther apart in solubility characteristics. This is exemplified in the previous example, the maltenes, the most soluble fraction has more common peaks with asphaltene fraction 1 than with the least soluble fraction (asphaltene fraction 3).


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The comparison of the assigned formulas in the fractions to the assigned formulas in the unfractionated field deposit indicates that there are 13103 more unique peak assignments in the fractions than in the deposit. This is probably due to the enrichment of species in the fractions that are not concentrated enough in the original deposit to be detected. Figure 2 shows the normalized distributions of the unique peaks as a function of the DBE/C in comparison to the whole distribution of assigned peaks in the original deposit. This figure shows that both distributions are similar, indicating that the additional peaks observed in the fractions cover the whole spectrum of aromaticities observed in the original deposit.

This suggests that the

fractionation does not provide additional information in terms of the general compositional distribution and average characteristics of the deposit. In Figure 3 the class distributions of the solubility fractions are shown. The most abundant class in the maltenes is the hydrocarbon HC class, while for the asphaltene fractions, the most abundant class is the S class. It is interesting to point out that according to Figure 3, class S is relatively more abundant in maltenes than in the asphaltene fractions. This is likely the effect of the lower efficiency of APPI to ionize molecules with low DBE. As maltenes contain a large number of low DBE species and they are not ionized efficiently, this leads to a larger relative amount for heteroatom-species in the maltenes. This effect is more noticeable for class S. Only small differences in the relative abundances in the compound classes have been observed for the fractions 1-3. For instance, from fraction 1 to fraction 3 class S2 is increasing while class N is decreasing. Figure 4 shows the relative abundance of the HC classes, Scontaining classes and N-containing classes for the fractions. Even though the preferential ionization of large DBE molecules affects the maltenes distribution greatly, the tendencies shown in Figure 4 are qualitatively correct. It can be seen that S-containing classes are similarly


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abundant in the asphaltene fractions, while nitrogen increases from maltenes to asphaltene fraction 3. DBE and Carbon Number Comparison. Figure 5 shows plots of DBE as a function of carbon number for HC, S, S2 and N-classes for the different solubility fractions. These plots show how the classes corresponding to maltenes occupy the largest compositional space, while the compositional spaces for asphaltene fraction classes are narrower. It is also clear the presence of some compositional gaps in the plots around C70. These gaps appear as the mass resolution drops with increasing mass. This means that some peaks in the high m/z range cannot be assigned properly. Additionally, in these plots it is also clear the big overlapping for classes and fractions with shifts towards larger DBEs as the fractions become less soluble. This is in accordance to the Boduszynski continuum model24 as illustrated in Figure 6a for HC-class. In this figure, the DBE distributions for the HC-class as a function of the solubility fraction are shown. It is clear that there is a shift to higher DBE values from maltenes to asphaltene fractions. As expected, this shift is more significant between maltenes and asphaltene fraction 1. It is also worth noticing that the classes become narrower as their solubility in hydrocarbons decreases (This is from maltenes to asphaltene fraction 3). In terms of carbon number distributions (Figure 6b), there is an increase in the carbon number distribution for the HC-class as it becomes less soluble from maltenes to asphaltene fraction 3. Similar results were obtained for other classes. In Figure 5, it can also be noticed that in terms of the compositional space, there are no significant differences between different classes belonging to the same fraction. This aspect is shown in Figure 7a, where the distributions for different classes belonging to the same fraction are shown. As it can be seen, only small differences are observed for the same class. This can


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indicate that the main driver for the solubility fractionation is hydrogen deficiency (DBE) and not the polar character induced by the presence of heteroatoms, in particular N and O. Carbon number distributions are very similar as well (Figure 7b). In Figures 8a and 8b the average values for DBE and carbon number as a function of the fractions are shown. These averages were calculated as weighted values based on relative abundances in the mass spectrum. Both figures show increases in the DBE as well as in the carbon number from maltenes to asphaltene fraction 3. However, the increase in carbon number is smaller than the change in DBE, indicating that size might not be as relevant as the DBE in the solubility separation of the fractions. The largest differences for both, DBE and carbon number are seen when maltenes are compared with asphaltene fractions. DBE values found in the present work are larger than similar values reported for deposits and asphaltenes in previous studies.4,10,15 This result points out to the diverse nature of asphaltenes from different sources. Comparison of Field Deposit and Heptane Asphaltenes. Figure 9a shows the comparison in class distributions for the field deposit and heptane extracted asphaltenes. At first glance, both distributions look similar. However, the field deposit is enriched in HC class, as well as in oxygen-class components while N-classes are more abundant in the heptane extracted asphaltenes. These results are consistent with previous studies that indicate a enrichment of oxygen species in field deposits in comparison with the crude oil15 while heptane extracted asphaltenes are enriched in N species and have less oxygen species in comparison with pressure drop asphaltenes10. In Figure 9b, DBE/C distributions are compared and the results indicate that the deposit is enriched in low DBE/C components, which are in agreement with the fact that the deposit contains trapped maltenes (around 16 wt% of the organic material in the deposit).5


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In terms of the comparison of heptane asphaltenes with the fractions, Figure 10 shows average DBEs and carbon numbers for the fractions and heptane asphaltenes calculated as the weighted response of all the assigned peaks. This comparison shows that the heptane asphaltenes are in average closer to asphaltene fraction 2 of the deposit. Average DBE/C is also closer to asphaltene fraction 2. This is in agreement with the previous study that indicates that the heptane asphaltenes closely resemble asphaltene fraction 2 of the deposit.5 Comparison of Average and Bulk Properties. In a previous publication, values for the bulk properties of the fractions, original field deposit and heptane asphaltenes were determined using conventional techniques.5 Figure 11 shows the comparison between average H/C ratios calculated using weighted elemental distributions based on relative intensity and bulk values obtained from elemental analysis. Additionally, we compare with the unweighted average obtained based on the assumption that the response factors might be different for different components and therefore the intensities do not correlate with concentration.11 The comparison of the three values derived from elemental analysis and weighted and unweighted calculations indicates that the calculated values show the right tendencies. However, it is clear that weighted values are closer to the bulk values than unweighted values except for maltenes where both calculated values are equally far away from bulk values. Results also show that unweighted values produce considerably higher H/C ratios than the bulk values except for maltenes. In contrast, weighted values are slightly lower than H/C bulk values but they are remarkably close for the asphaltene fractions as well as for the oilfield deposit and heptane asphaltenes. This might be explained as the result of the preferential ionization of the most aromatic molecules (high DBE) that are abundant in the asphaltene fractions, deposit and heptane asphaltenes. In contrast,


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aromatic molecules with high DBE are less abundant in maltenes, which explains the large differences observed in Figure 11. Figure 12 shows the comparison between weighted molecular weights calculated for the fractions from the MS data and molecular weights determined using SEC (Size Exclusion Chromatography). Calculated weighted molecular weights for the fractions are in the range 600700 Da. These values are close to those obtained using SEC. Both techniques show a slightly increase of the average mass from maltenes to fraction 3.

Weighted average densities were calculated for the fractions using MS data based on hydrogen content for each assigned peak. Then, the density was determined using the following correlation developed previously for asphaltene fractions:23 (2)

ρ=-0.064*H+1.6793

where H represents the hydrogen content. The error in the correlation is around 0.7%. Once the density for each assigned peak is calculated, the weighted average is determined based on the relative abundance of each species. Figure 13 shows the comparison between calculated densities and experimental values published previously.5 The calculated average densities match remarkably well the bulk values for the asphaltene fractions with errors between 0.5 to 1.8 %. For maltenes, the difference between calculated and bulk values is much larger (15 %) due to the preferential ionization of the more aromatic molecules. The lower hydrogen content of these molecules produces a larger average density. These results support the idea that molecular distributions produced by APPI MS are a good representation of the real distribution of asphaltenes. This finding indicates that


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this technique can be particularly useful to study asphaltenes and asphaltene deposits where the vast majority of molecules are highly aromatic. Additionally, it can represent the first step towards a better understanding of the physical/chemical behavior of asphaltenes in terms of their detailed molecular composition.


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CONCLUSIONS The results support the idea that APPI FT-ICR MS can be particularly useful to study asphaltenes and asphaltenic deposits that are highly aromatic since the distributions obtained produce average values that closely match bulk data. Weighted average values obtained for the distributions showed a better match with bulk properties than unweighted values. The study of the fractions also revealed that additional assigned species in the fractions cover the whole spectrum of aromaticities observed in the original deposit showing a similar distribution to the distribution of the deposit. This suggests that the fractionation does not provide additional information in terms of the general compositional distribution and average characteristics of the deposit. The deposit is enriched in molecules with low aromaticity in comparison to heptane asphaltenes extracted from the crude oil. These low aromaticity molecules seem to correspond with trapped maltenes. Also, the deposit is enriched in oxygen-class components while heptane asphaltenes have more nitrogen containing components.


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ACKNOWLEDGMENTS E. Rogel would like to thank Dr. C. Ovalles and Dr. Michael Moir for their valuable comments.


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4. Juyal, P., McKenna, A. M.; Fan, T.; Cao, T.; Rueda-Velásquez, R. I., Fitzsimmons, J. E.; Yen, A.; Rodgers, R. P.; Wang, J.; Buckley, J. S.; Gray, M. R.; Allenson, S. J.; Creek, J. Energy Fuels, 2013, 27, 1899-1908. 5. Rogel, E.; Miao, T.; Vien, J.; Roye, M. Fuel 2015, 147, 155-160. 6. Rogel, E.; Ovalles, C.; Moir, M.; Vien, J.; Morazan, H. “Solubility Characterization of Asphaltene Deposits” SPE International Symposium on Oilfield Chemistry, The Woodlands, Texas, USA, 13–15 April 2015. SPE -173757. 7. Cho, Y.; Kim, Y. H.; Kim, S. Anal. Chem. 2011, 83, 6068-6073. 8. Podgorski, D. C.; Corilo, Y. E.; Nyadong, L.; Lobodin, V. V.; Bythell, B. J.; Robbins, W. K.; McKenna, A. M.; Marshall, A. G.; Rodgers, R. P. Energy Fuels 2013, 27, 1268-1276. 9. Cho, Y.; Jin, J. M.; Witt, M.; Birdwell, J. E.; Na, J.; Roh, N.; Kim, S. Energy Fuels 2013, 27, 1830-1837. 10. Klein, G.C.; Kim , S.; Rodgers, R. P.; Marshall, A. G.; Yen, A.; Asomaning, S. Energy Fuels 2006, 20,1965-1972. 11. Gaspar, A.; Zellermann, E.; Lababidi, S.; Reece, J.; Schrader, W. Anal. Chem. 2012, 84, 5257-5267.


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12. Owen, B.; Gao, J.; Amundson, L.; Archibold, E.; Tan, X.; Azyat, K.; Tykwinski, R.; Gray, M.; Kenttämaa, H. Rapid Commun. Mass Spectrom. 2011, 25, 1924−1928. 13. Jarrell, Tiffany M.; Jin, C.; Riedeman, J. S.; Owen, B. C.; Xiaoli, T.; Scherer, A.; Tykwinski, R. R.; Gray, M. R.; Slater, P.; Kenttämaa, H. I. Fuel 2014, 133, 106-114. 14. Hurt, M. R.; Borton, D. J.; Choi, H. J.; Kenttämaa, H. I. Energy Fuels 2013, 27, 3653-3658. 15. Klein, G.C.; Kim , S.; Rodgers, R. P.; Marshall, A. G.; Yen, A. Energy Fuels 2006, 20,19731979. 16. Juyal, P.; Yen, A. T.; Rodgers, R. P.; Allenson, S.; Wang, J.; Creek, J. Energy Fuels 2010, 24, 2320-2326. 17. Rogel, E.; Witt, M.; Moir, M. Energy Fuels, 2015, 29, 4201-4209. 18. Ovalles, C.; Rogel, E.; Moir, M.; Thomas, L.; Pradhan, A. Energy Fuels 2012, 26, 549-556. 19. American Society for Testing and Materials, Standard Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum Products – IP143/01 ASTM D6560, 2005. 20. Guzman A.; Bueno A.; Carbognani, L. Petroleum Science and Technology 2009, 27, 801816. 21. Kauppila, T.; “Atmospheric Pressure Photoionization-Mass Spectrometry, Academic Dissertation, University of Helsinki, 2004. 22. Purcell, J. M.; Hendrickson, C. L.; Rodgers, R. P.; Marshall, A. G. J Am Soc Mass Spectrom 2007, 18, 1682-1689. 23. Rogel, E.; Roye, M.; Vien, J.; Miao. T. Energy Fuels 2015, 29, 2143-2152. 24. Boduszynski, M. M. Energy Fuels 1987, 1, 2-11.


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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 ACS Paragon Plus Environment

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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

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TABLE LIST Table 1. Counts of assigned molecular formulas for the solubility fractions (bold) and common peak assignments.


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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

FIGURE LIST Figure 1. Mass spectra of solubility fractions of the field deposit. Figure 2. Normalized distributions of the unique peaks found in the fractions but not in the field deposit as a function of DBE/C in comparison with the whole distribution of assigned peaks in the field deposit. Figure 3. Class distribution of the solubility fractions. Figure 4. Relative abundance of HC-classes, S-containing classes and N-containing classes of the solubility fractions. Figure 5. DBE as a function of carbon number for HC, S, S2 and N-classes for the different solubility fractions. Figure 6. Distributions for the HC-class as a function of the solubility fraction a) DBE distribution, b) Carbon number distribution. Figure 7. Distributions for different classes belonging to asphaltene fraction 2 a) DBE distribution, b) Carbon number distribution. Figure 8. Average values for the classes: HC, S, S2, N and O as a function of the solubility fraction a) DBE, b) Carbon number. Figure 9. Comparison of field deposit and heptane asphaltenes. a) Class Distributions, b) DBE/C distributions. Figure 10. Comparison of average DBE and carbon numbers for solubility fractions and heptane asphaltenes. Figure 11. Comparison of average H/C calculated based on MS data and bulk H/C from elemental analysis. Figure 12. Comparison of average molecular weights calculated based on MS data and bulk molecular weights determined using Size Exclusion Chromatography (SEC) Figure 13. Comparison of average density values calculated based on MS data and experimental bulk values determined previously.15


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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

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TABLES AND FIGURES


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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

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Table 1 Maltenes

Fraction 1

Fraction 2

Fraction 3

Maltenes

11128

8126

6127

5654

Fraction 1

8126

10167

6999

6240

Fraction 2

6127

6999

8633

6531

Fraction 3

5654

6240

6531

8917


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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

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Maltenes

Asphaltene Fraction 1



Figure 1


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1.0 0.9 Deposit

0.8

Normalized assigned peaks

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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0.7 Unique assigments in the solubility fractions

0.6 0.5 0.4 0.3 0.2 0.1 0.0 0

0.1

0.2

0.3

0.4

0.5 DBE/C

0.6

Figure 2


0.7

0.8

0.9

1

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35.0 Maltenes

30.0

Fraction 1 Fraction 2

25.0

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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Fraction 3

20.0

15.0

10.0 5.0

0.0 HC

S

S2

O

OS O2 Chemical Classes

Figure 3


N

NS

NO

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60.0

50.0 HC

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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40.0

S-contaning classes N-containing classes

30.0

20.0

10.0

0.0 Maltenes

Fraction 1

Fraction 2

Figure 4


Fraction 3

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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

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Figure 5


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1.0 Maltenes 0.9

Fraction 1

0.8

Fraction 2

Normalized Response

Fraction 3 0.7

a)

0.6 0.5 0.4 0.3 0.2 0.1 0.0 0

2

4

6

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

DBE 1.0

Maltenes

0.9

Fraction 1 Fraction 2

0.8

Fraction 3

Normalized Response

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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0.7

b) 0.6 0.5 0.4 0.3 0.2 0.1 0.0 5 8 11 14 17 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74 77 80 83 86 89

Carbon Number

Figure 6


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1.0 0.9

Normalized Response

HC 0.8

S

0.7

S2 N

0.6

O

0.5 0.4

a)

0.3 0.2 0.1 0.0

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61

DBE 1.0 0.9 HC

Normalized Response

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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0.8

S

0.7

S2 N

0.6

O

0.5 0.4

b)

0.3 0.2 0.1 0.0 5 8 11 14 17 20 23 26 29 32 35 38 41 44 47 50 53 56 59 62 65 68 71 74 77 80 83 86 89

Carbon Number

Figure 7


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35

30

25

DBE

a)

20

HC S S2

15

N O

10 Maltenes

Fraction 1

Fraction 2

Fraction 3

56

54

Carbon Number

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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52

50

48

HC S S2

46

b)

N O

44 Maltenes

Fraction 1

Fraction 2

Figure 8


Fraction 3

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30 Heptane Asphaltenes

25

Relative Abundance

Deposit 20

15

10

5

0 HC

S

S2

O

OS O2 Chemical Classes

N

NS

NO

1.0 0.9

Heptane Asphaltenes

0.8

Normalized Response

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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Deposit

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0

0.1

0.2

0.3

0.4

0.5 0.6 DBE/C

0.7

Figure 9


0.8

0.9

1.0

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35

53

33

52

31

51

29

50

27

49

25

48

23

47 DBE

21

46

Carbon Number

19

45

17

44

15

43 Maltenes

Fraction 1

Fraction 2

Fraction 3

Figure 10


Heptane Asphaltenes

C

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

DBE

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1.65 Elemental Analysis 1.55

Weighted Average MS Unweighted Average MS

1.45 1.35

H/C ratio

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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1.25 1.15 1.05 0.95 0.85 0.75 Maltenes

Fraction 1

Fraction 2

Fraction 3

Figure 11


Deposit

Heptane Asphaltenes

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750

700

Molecular Weight (Da)

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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650

600 SEC MS

550

500 Maltenes

Fraction 1

Fraction 2

Figure 12


Fraction 3

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1.30 1.25 1.20

Density (g/mL)

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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1.15 1.10 1.05 Bulk Density 1.00 Weighted Density (MS) 0.95 0.90 Maltenes

Fraction 1

Fraction 2

Figure 13


Fraction 3

Atmospheric Pressure Photoionization Coupled to Fourier Transform

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