Understanding Shale Oil Hydrotreatment with Composition Analysis

Article pubs.acs.org/EF

Understanding Shale Oil Hydrotreatment with Composition Analysis Using Positive-Ion Mode Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Kui Zhang,†,‡ Jian Yu,† Shiqiu Gao,† Changming Li,† and Guangwen Xu*,†,§ †

State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China ‡ University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China § Southwest Research & Design Institute of Chemical Industry Company, Limited, Chengdu, Sichuan 610225, People’s Republic of China ABSTRACT: Positive-ion mode of atmospheric pressure photoionization (APPI) coupled with a 9.4 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been applied to the characterization of shale oil from pyrolysis and its hydrotreatment. The hydrotreated shale oil was obtained through reactions over catalysts Ni−Mo, Ni−W, or Co−Mo. It was found that N1 and N1O1 species are the dominant N compounds and S1 species is the dominant S compound in shale oil from pyrolyzing Huadian oil shale. The primary aromatic hydrocarbons (AHCs) are mono- and double-ring aromatics. After hydrotreatment, both S and N compounds are effectively removed and the catalyst Ni−Mo shows the best performance in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). The AHC species, especially the mono-ring aromatics, increases as a result of the transformation of N1, N1O1, and S1 species into AHC species through hydrotreatment. Indole, carbazole, acridine, and their derivatives are preserved as N1 species. The reactions of HDN for shale oil were further analyzed by considering the transformation between N1O1 and N1 species.

1. INTRODUCTION As an unconventional energy resource, shale oil from pyrolyzing oil shale has attracted much attention all over the world for its huge reserve on earth, which is predicted to be about 4 times the proven petroleum reserve.1,2 In comparison to petroleum, shale oil is rather complex as an organic mixture composed of hydrocarbons and organic compounds containing heteroatoms (S, N, O, etc.). It has a relatively high nitrogen content.3−6 The heteroatom-containing compounds usually cause problems in using shale oil, including fuel instability in transportation or storage, catalyst poisoning in downstream treatment, and fouling and pollutant emission in utilization.7 Many upgrading processes, such as hydrotreatement, are developed to remove S, N, and O species from shale oil.8−11 To understand shale oil and facilitate utilization technology development, it is important to characterize various types of shale oil composition at the molecular level. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been considered to be a new tool for characterizing samples of a complex mixture, such as petroleum or shale oil, at the molecular level.12,13 Its ultrahigh resolution enables unique elemental or compositional assignment and identification of thousands of species in a single mass spectrum.14−18 Different ion sources coupled with FT-ICR MS, such as electrospray ionization (ESI) and atmospheric pressure photoionization (APPI), have been applied for molecular characterization of samples with complex organic mixtures.19−24 ESI FT-ICR MS has been widely used to realize detailed speciation of partial polar constituents in petroleum or shale oil.3,12,13,17,24,25 The ions [M − H]− or [M + H]+ can be © 2017 American Chemical Society

formed by deprotonation or protonation when applying ESI to acidic molecular species typified by compounds with carboxylic or sulfonic acid groups, non-basic species represented by pyrrolic nitrogen, and basic species, such as pyridinic nitrogen.16,18,19,26,27 However, the S-containing compounds, such as thiophenes, that are not sufficiently acidic or basic are difficult to be efficiently ionized by ESI, unless the electrophilic attack on sulfur species is carried out by a strong alkylating reagent to form S-alkyl sulfonium salts (in solution) before ESI.28−30 In comparison, APPI can efficiently ionize gas-phase nonpolar and polar species through direct photon ionization or proton transfer.20,21 Purcell et al.31 used ESI and APPI coupled with a 9.4 T FT-ICR MS to characterize S-containing compounds in a vacuum bottom residue. They found that in comparison to APPI, the methylation followed by ESI is not suitable for specification of sulfur compounds with a high-number carbon. In addition, efficient signals for both pyrrolic and pyridinic nitrogen are generated in a single mass spectrum by positiveion APPI,21 but two mass spectra are needed to fully represent these signals by positive- and negative-ion ESI, respectively.16,26 For non-polar species, such as aromatic hydrocarbons (AHCs), only APPI produces mass spectral signals compared to ESI.31 Because direct photoionization is usually not very efficient,32 the addition of a dopant, such as toluene, can enhance ionization efficiency through proton-transfer and chargeReceived: October 28, 2016 Revised: December 4, 2016 Published: January 14, 2017 1362

DOI: 10.1021/acs.energyfuels.6b02807 Energy Fuels 2017, 31, 1362−1369

Article

Energy & Fuels exchange reactions. This study first applies positive-ion mode APPI with toluene as dopant assistance coupled with a 9.4 T FT-ICR MS for the characterization of shale oil (SO) obtained from pyrolysis of Huadian oil shale and also hydrotreated shale oil (HSO). For hydrotreatment, three catalysts Ni−Mo, Ni−W and Co−Mo, have been tested to investigate the influences of metal active components on species transformation. Their corresponding HSOs are marked as HSO-NiMo, HSO-NiW, and HSO-CoMo, respectively. Given that APPI mass analysis can provide possible core structure information on species based on double-bond equivalence (DBE) values,23,26,33 the obtained transformation of species, e.g., N1, N1O1, S1, and AHCs, based on the APPI mass analysis will facilitate the design and development of better hydrotreatment catalyst and technology for upgrading shale oil.

Table 2. Properties of Oil Samples SO, HSO-NiMo, HSONiW, and HSO-CoMo

2.1. Catalysts and Catalyst Pretreatment. The alumina carriers used in the three catalysts were the same and supplied by a company in Fushun, China. The alumina carriers were impregnated with nickel or cobalt nitrate and ammonium molybdate or ammonium metatungstate in ammonia solution. They were dried at 120 °C for 3 h and calcined at 450 °C for 5 h. Three catalysts, Ni−Mo, Ni−W, and Co−Mo, were prepared. The composition of the catalyst and physical properties are shown in Table 1. Before reaction, all catalysts

Table 1. Properties of Ni−Mo, Ni−W, and Co−Mo Catalysts property

Ni−Mo

Ni−W

Co−Mo

1.044 3.132 70.00 178.371 0.576

1.044 3.132 55.43 150.286 0.419

1.044 3.132 69.99 208.626 0.591

SO 0.8469

HSO-NiMo HSO-NiW 0.8136

0.8175

HSO-CoMo 0.8204

7.186

6.564

6.746

7.107

0.396 0.984

0.006 0.080

0.030 0.105

0.013 0.169

in the samples of SO and SO + furan were analyzed using a Excalibur 3100 FTIR spectrometer (Varian Medical Systems, Inc.). The film of the sample was created by placing a drop of SO or SO + furan on the transparent KBr plate. The FTIR spectra for the two samples were obtained at 4 cm−1 resolution and collected in the range of 4000−400 cm−1. 2.4. APPI FT-ICR MS Analysis. All tested oil samples, including SO, HSO-NiMo, HSO-NiW, and HSO-CoMo, were dissolved in toluene of high-performance liquid chromatography (HPLC) grade and further diluted to 0.5 mg/mL. The analysis were conducted using a 9.4 T Apex Qe FT-ICR MS (Bruker Daltonics, Inc.), and APPI+ (Agilent Technologies, Inc.) was the ionization source used. A diluted sample was directly injected into APPI via a fused-silica capillary connected to a syringe pump (Hamilton Corp.) that ran at a flow rate of 360 μL/h. Nitrogen was used as the nebulizing and drying gas. The operation parameters of APPI analysis include a nebulizing temperature of 400 °C at a gas flow rate of 1.0 L/min, a drying gas temperature of 200 °C at a gas flow rate of 4.0 L/min, and its skimmer voltage of 30.0 V. In total, 256 scans were accumulated and, subsequently, averaged to improve the signal-to-noise (S/N) ratio of the obtained spectrum. For each spectrum, 4 million data points were obtained to achieve high resolution and mass accuracy. The mass-tocharge (m/z) range was recorded from 100 to 1000 for measured SO, HSO-NiMo, HSO-NiW, and HSO-CoMo. The APPI FT-ICR MS spectra were externally calibrated through Tuning Mix (Agilent Corp.). The peaks with a S/N ratio above 6 were chosen for data analysis. A chemical molecular formula CcHhNnOoSs was calculated according to the m/z values within ±1 ppm. The DBE values, referring to the number of rings plus double bonds in the molecular structure, were calculated for CcHhNnOoSs according to the equation DBE = c − h/2 + n/2 + 1.

2. EXPERIMENTAL SECTION

NiO or CoO (mol kg−1 of Al2O3) MoO3 or WO3 (mol kg−1 of Al2O3) Al2O3 (wt %) surface area (m2 g−1) pore volume (mL g−1)

property specific gravity at 4 °C element (wt %) C/H weight ratio S N

were sulfurized by carbon disulfide with kerosene as the solvent oil in the autoclave reactor at a hydrogen pressure of 10 MPa and temperature of 350 °C by a standard procedure. The sulfurized catalysts were maintained under nitrogen prior to use. 2.2. Sample Preparation. The tested shale oil was from an oil shale processing plant in Huadian, China. Hydrotreatment of the shale oil was carried out in a 500 mL autoclave, as shown in Figure 1. All

3. RESULTS AND DISCUSSION 3.1. APPI FT-ICR Mass Spectra. Figure 2 shows the APPI+ FT-ICR mass spectra of oil samples SO, HSO-NiMo, HSONiW, and HSO-CoMo. It can be seen that the mass distributions of SO, HSO-NiMo, HSO-NiW, and HSO-

Figure 1. Autoclave for testing hydrotreatment of shale oil (1, H2 mass flow meter; 2, buffer tank; 3, high-pressure autoclave; 4, water tank). hydrotreatment tests were under the same reaction conditions but over three sulfurized catalysts of Ni−Mo, Ni−W, and Co−Mo with alumina of the same weight as carriers. The reaction conditions are at a pressure of 10 MPa, temperature of 360 °C, catalyst/oil ratio in volume of 0.1, H2/catalyst ratio in volume of 600 h−1 at normal temperature and pressure, and reaction time of 10 h. Table 2 lists the major properties of virgin SO and HSOs of HSO-NiMo, HSO-NiW, and HSO-CoMo. 2.3. FTIR Analysis. The sample marked as SO + furan is prepared by adding a certain amount of furan into the SO, and the furan content of the sample SO + furan is 600 ppm. The chemical groups presented

Figure 2. APPI+ FT-ICR mass spectra of oil samples SO, HSO-NiMo, HSO-NiW, and HSO-CoMo. 1363


Article

Energy & Fuels

Figure 3. Peaks at m/z of 309.2060−309.2480 and 350.2860−350.3260 obtained from APPI+ FT-ICR mass spectra of oil samples SO, HSO-NiMo, HSO-NiW, and HSO-CoMo.

analysis. The relative abundance is derived from summing and normalizing to 100% for all signal abundances of heteroatom species and AHC species in a spectrum together, and the relative abundance of each species is expressed as a corresponding percentage thereof. For SO, N1 species is the predominant N compound and N1O1 species comes next. Some other N species are also detected, including N1O2, N2, N1S1, N1O1S1, and N1O3. Among detected S compounds, S1 species takes the first and there are very few S2 species. In hydrotreated shale oils HSO-NiMo, HSO-NiW, and HSOCoMo, N1 species greatly reduced but is still the predominant N compound. In terms of relative abundances, there are very few other N species in hydrotreated oils. For example, N1O1 and N1O2 species greatly reduced, while N2, N1S1, N1O1S1, and N1O3 species almost disappeared. Of S compounds, S1 species still exists but its relative abundance is very low. The relative abundance of S2 species is close to zero. In addition, the contents of S and N species in HSO-NiMo are lowest among all hydrotreated oil samples. Thus, S and N compounds in shale oil can be effectively removed through the hydrotreatment process, and the Ni−Mo catalyst showed good capability for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions. The reaction performances of S and N are consistent with the data listed in Table 2. However, the distribution of S and N compound species as shown in Figure 4 is larger than that listed in Table 2 as a result of the possible reason for low detectability of paraffin for APPI+ FT-ICR MS. Because the relative abundances of S1 and N1O1 species are very low in hydrotreated shale oil, herein, the analysis for S1 and N1O1 species is made only for SO. As the primary S and N compounds, both S1 and N1O1 species are emphatically analyzed in Figure 5. Panels a and b of Figure 5 show DBE values as a function of the carbon number for S1 and N1O1 species present in SO. The plots are based on APPI+ FT-ICR mass spectra, and the size of every coordinate dot represents the relative abundance of the compound with the DBE and carbon number indicated in the figure. For S1 species in Figure 5a, the DBE values are in the range of 3−15 and the carbon number is in the range of 15−33. Their relative abundances

CoMo are primarily located in the same range of 100−700, and their distribution peaks are all centered at m/z of about 344. SO has 23 653 peaks in such a m/z range, slightly more than the other samples with hydrotreatment. In comparison to SO, the relative intensities of partial peaks for HSO-NiMo, HSO-NiW, and HSO-CoMo decrease more apparently after hydrotreatment. Figure 3 shows the local peaks at m/z ranges of 309.2060− 309.2480 and 350.2860−350.3260 obtained from APPI+ FTICR mass spectra of oil samples SO, HSO-NiMo, HSO-NiW, and HSO-CoMo. In Figure 3, the peaks with S/N ratios above 6 are marked with molecular ion formula. In comparison to SO, the peaks of C21H27NO+ and C23H42S+ almost disappeared as a result of hydrotreatment, while C22H31N+ became weaker mainly for HSO-NiMo and HSO-NiW. The intensities of C26H38+ turned to be stronger for all hydrotreated oils. In addition, all peaks with S/N ratios below 6 became weaker via the hydrotreatment process. 3.2. Heteroatom Species. Figure 4 shows the distribution of heteroatom species obtained from APPI+ FT-ICR MS

Figure 4. Distribution of heteroatom species obtained from APPI+ analysis of oil samples SO, HSO-NiMo, HSO-NiW, and HSO-CoMo. The heteroatom species are defined as the compounds containing heteroatoms, besides C and H elements; e.g., N1O1S1 species are the compounds containing one N atom, one O atom, and one S atom, except C and H atoms in their molecular formula. 1364


Article

Energy & Fuels

Figure 5. DBE as a function of the carbon number for (a) S1 and (b) N1O1 species in SO based on APPI+ FT-ICR mass spectra and suggested core structures of (c) S1 and (d) N1O1 species in SO based on DBE values. The dot size is proportional to the relative abundance of the specific compound in the sample.

SO + furan, and it also gives evidence of the furan ring presented in the SO. As Figure 6 shows, the FTIR spectra of the SO and SO + furan are almost the same. There is no new peak appearing in the FTIR spectrum for the addition of furan, which means that the shale oil may contain the derivatives of furan. Panels a−d of Figure 7 show DBE values as a function of the carbon number for N1 species in SO, HSO-NiMo, HSO-NiW, and HSO-CoMo obtained from APPI+ FT-ICR mass spectra. In SO, the N1 species cover the carbon number in the range of 11−43 and DBE values in the range of 4−19. Those with DBE values of 4, 6, 7, 9, 10, 11, and 12 have higher relative abundances than the others, and Figure 7e shows the core structures suggested for such DBE values. After hydrotreatment, the relative abundances of major N1 species evidently reduced for all hydrotreated oils, especially HSO-NiMo. Thus, the Ni−Mo catalyst should have the best catalytic activity in removal of N1 species. For HSO-NiMo, its N compounds with DBE values of 6, 9, and 10 still take certain abundances to be the dominant N1 species. Their possible core structures are indole, carbazole, acridine, and their derivatives (see Figure 7e). Literature studies show that indole, carbazole, and their derivatives are difficult to be removed by HDN for their basicity lower than basic nitrogen species, such as quinoline.38−41 Although acridine belongs to basic nitrogen species, hydrodeoxygenation (HDO) of N1O1 (DBE of 12) may contribute to its high content in hydrotreated shale oil. Because the furan ring is more easily saturated and opened than the aromatic ring or nitrogen-containing heterocyclic ring,42 N1O1 species can be readily converted into N1 after removal of oxygen. Figure 8 shows the transformation between N1O1 and N1 species, the primary N compounds in shale oil (see Figure 4), to further understand HDN of shale oil. The N1 species with high DBE values can be converted first into N1 species with low DBE values by hydrodearomatization (HDA).

follow the DBE order of 3, 4, 6, and 7, with the compound at DBE of 3 taking the highest relative abundance. The possible compounds of S1 species at DBE values of 3, 4, 6, and 7 are thiophene, benzothiophene, mercaptobenzene, naphthalenethiol, and their derivatives, as suggested in Figure 5c. These S1 species at DBE values of 3, 4, 6, and 7, such as C23H42S at DBE of 3 (Figure 3), are more easily removed than dibenzothiophene or 4,6-dimethyldibenzothiophene by HDS.34−37 The relative abundances of such S1 species, thus, greatly reduced in Figure 4. For N1O1 species, their DBE values are in the range of 4−19 and the carbon number is in the range of 14−37. The compounds at DBE of 8−13 are the primary N1O1 species for their high relative abundances, especially at DBE values of 9 and 12. Figure 5d shows the possible core structures for the N1O1 species compounds with different DBE values. In Figure 5d, the proposed molecular structure of N1O1 species contains the furan ring based on the data obtained from APPI FT-ICR MS analysis. Figure 6 shows the FTIR spectra of the SO and

Figure 6. FTIR spectra of the SO and SO + furan. 1365


Article

Energy & Fuels

Figure 7. DBE as a function of the carbon number for N1 species in (a) SO, (b) HSO-NiMo, (c) HSO-NiW, and (d) HSO-CoMo from APPI+ FTICR mass spectra and (e) suggested core structures of N1 species based on DBE values. The dot size is proportional to the relative abundance of the specific compound in the sample.

9, and 10. As a result, the transformation of N1O1 into N1 species is also a required function of HDN for shale oil. 3.3. AHC Species. Panels a−d of Figure 9 show DBE values of AHC species, as a function of the carbon number, for SO, HSO-NiMo, HSO-NiW, and HSO-CoMo. In SO, its DBE values are in the range of 4−19 and the carbon number is in the range of 13−42. The primary AHC species are the compounds with DBE values of 4, 5, 6, and 7, as the primary AHCs in hydrotreated shale oil, especially those with DBE values of 4 and 5, shown in panels b−d of Figure 9. Figure 9e shows their suggested core structures based on DBE values. The AHC species with less rings have more difficulties for their hydrotreatment.43−45 In HSO-NiMo, HSO-NiW, and HSOCoMo, their relative abundances are thus enlarged for the AHC species with DBE values of 4 and 5 as a result of the transformation of species with DBE values above 5 via hydrotreatment. Figure 9f reveals that the relative abundances of AHC species were enhanced for all hydrotreated oils and HSO-NiMo had the highest relative abundance. The reason may be that the other species, such as N1, N1O1, and S1 species, are possibly transferred to AHC species through hydrotreatment, and the catalyst Ni−Mo has the best activity for catalyzing the transformation.

Figure 8. Transformation between N1O1 and N1 species in the hydrotreatment process.

Then, removal of nitrogen generates AHC species, while the removal of oxygen from N1O1 species forms N1 species in hydrotreated shale oil, such as N1 species with DBE values of 7, 1366


Article

Energy & Fuels

Figure 9. DBE as a function of the carbon number for AHC species in (a) SO, (b) HSO-NiMo, (c) HSO-NiW, and (d) HSO-CoMo from APPI+ FT-ICR mass spectra, (e) suggested core structures of AHC species based on DBE values, and (f) relative abundance of AHC species. The dot size is proportional to the relative abundance of the specific compound in the sample.

AHC species with one or two rings as byproducts, the relative abundances of AHC species with DBE values of 4 and 5 are enhanced for HSO-NiMo, HSO-NiW, and HSO-CoMo compared to that in SO. The implied results are consistent with the changes of dot sizes for AHC species with DBE values of 4 and 5, as shown in panels a−d of Figure 9.

As a summary, Figure 10 shows the transformation mechanism among N1, N1O1, S1, and AHC species in hydrotreatment. All N1, N1O1, and S1 species can react with H2 to produce H2S, NH3, and H2O on the catalyst surface while generating AHC species. The N1, N1O1, and S1 compounds listed in Figure 10 are the primary N1, N1O1, and S1 species in SO. As a result of their transformation in hydrotreatment into

4. CONCLUSION Shale oil samples SO and their hydrotreated shale oils of HSONiMo, HSO-NiW, and HSO-CoMo were characterized using positive-ion mode APPI FT-ICR MS. There are more than 20 000 peaks detected in the obtained spectra. In SO, N1 and N1O1 species are identified as the dominant N compounds and the other N species included, for example, N1O2, N2, N1S1, N1O1S1, and N1O3. Of sulfur (S) compounds, the S1 species is the first type because there are very few S2 species. The primary AHC species are mono- and double-ring aromatics. The possible structures of primary S1 species are thiophene, benzothiophene, mercaptobenzene, naphthalenethiol, and their derivatives. The compounds N1O1 at DBE values of 8− 13 are the primary N1O1 species, especially those with DBE values of 9 and 12.

Figure 10. Transformation between N1, N1O1, S1, and AHC species in hydrotreatment. 1367


Article

Energy & Fuels

(10) Johannes, I.; Luik, H.; Kruusement, K. Mathematical models for kinetics of batchwise hydrogenation of shale oil. Fuel Process. Technol. 2006, 87, 711−716. (11) Landau, M. V. Deep hydrotreating of middle distillates from crude and shale oils. Catal. Today 1997, 36, 393−429. (12) Marshall, A. G.; Rodgers, R. P. Petroleomics: The Next Grand Challenge for Chemical Analysis. Acc. Chem. Res. 2004, 37, 53−59. (13) Rodgers, R. P.; Schaub, T. M.; Marshall, A. G. Petroleomics: MS Returns to Its Roots. Anal. Chem. 2005, 77, 20 A−27 A. (14) Qian, K.; Robbins, W. K.; Hughey, C. A.; Cooper, H. J.; Rodgers, R. P.; Marshall, A. G. Resolution and Identification of Elemental Compositions for More than 3000 Crude Acids in Heavy Petroleum by Negative-Ion Microelectrospray High-Field Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2001, 15, 1505−1511. (15) Qian, K.; Rodgers, R. P.; Hendrickson, C. L.; Emmett, M. R.; Marshall, A. G. Reading Chemical Fine Print: Resolution and Identification of 3000 Nitrogen-Containing Aromatic Compounds from a Single Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrum of Heavy Petroleum Crude Oil. Energy Fuels 2001, 15, 492−498. (16) Hughey, C. A.; Rodgers, R. P.; Marshall, A. G. Resolution of 11 000 Compositionally Distinct Components in a Single Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrum of Crude Oil. Anal. Chem. 2002, 74, 4145−4149. (17) Bae, E.; Na, J.-G.; Chung, S. H.; Kim, H. S.; Kim, S. Identification of about 30 000 Chemical Components in Shale Oils by Electrospray Ionization (ESI) and Atmospheric Pressure Photoionization (APPI) Coupled with 15 T Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) and a Comparison to Conventional Oil. Energy Fuels 2010, 24, 2563−2569. (18) Miettinen, I.; Mäkinen, M.; Vilppo, T.; Jänis, J. Compositional Characterization of Phase-Separated Pine Wood Slow Pyrolysis Oil by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2015, 29, 1758− 1765. (19) Klein, G. C.; Angström, A.; Rodgers, R. P.; Marshall, A. G. Use of Saturates/Aromatics/Resins/Asphaltenes (SARA) Fractionation To Determine Matrix Effects in Crude Oil Analysis by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2006, 20, 668−672. (20) Robb, D. B.; Covey, T. R.; Bruins, A. P. Atmospheric Pressure Photoionization: An Ionization Method for Liquid Chromatography− Mass Spectrometry. Anal. Chem. 2000, 72, 3653−3659. (21) Purcell, J. M.; Hendrickson, C. L.; Rodgers, R. P.; Marshall, A. G. Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry for Complex Mixture Analysis. Anal. Chem. 2006, 78, 5906−5912. (22) Chiaberge, S.; Guglielmetti, G.; Montanari, L.; Salvalaggio, M.; Santolini, L.; Spera, S.; Cesti, P. Investigation of Asphaltene Chemical Structural Modification Induced by Thermal Treatments. Energy Fuels 2009, 23, 4486−4495. (23) Kim, E.-K.; No, M.-H.; Koh, J.-S.; Kim, S.-W. Compositional characterization of petroleum heavy oils generated from vacuum distillation and catalytic cracking by positive-mode APPI FT-ICR mass spectrometry. Mass Spectrom. Lett. 2011, 2, 41−44. (24) Jin, J. M.; Kim, S.; Birdwell, J. E. Molecular Characterization and Comparison of Shale Oils Generated by Different Pyrolysis Methods. Energy Fuels 2012, 26, 1054−1062. (25) Chen, X.; Shen, B.; Sun, J.; Wang, C.; Shan, H.; Yang, C.; Li, C. Characterization and Comparison of Nitrogen Compounds in Hydrotreated and Untreated Shale Oil by Electrospray Ionization (ESI) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Energy Fuels 2012, 26, 1707−1714. (26) Purcell, J. M.; Rodgers, R. P.; Hendrickson, C. L.; Marshall, A. G. Speciation of Nitrogen Containing Aromatics by Atmospheric Pressure Photoionization or Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. J. Am. Soc. Mass Spectrom. 2007, 18, 1265−1273.

After catalytic hydrotreatment, both S and N compounds in shale oil are effectively removed. The Ni−Mo catalyst exhibited the best catalytic performance for HDS and HDN. In hydrotreated shale oil, N1 species reduced but is still the dominant N compound. The primary N1 species are indole, carbazole, acridine, and their derivatives, and all other N species are very few. In hydrotreated oils, the content of S1 species is very low and that of S2 species is close to zero. For AHC species of mono- and double-ring aromatics, they have still high relative abundances, especially the mono-ring aromatics. Because of the high relative abundances of N1 and N1O1 species in shale oil, the transformation between N1O1 and N1 species enabled a better understanding of HDN for shale oil. The relative abundances of AHC species are enhanced after hydrotreatment as a result of the transformation of N1, N1O1, and S1 species into AHC species via hydrotreatment. The Ni− Mo catalyst manifested the best performance in such a transformation.

■

AUTHOR INFORMATION

Corresponding Author

*Telephone: +86-10-82544886. Fax: +86-10-82629912. E-mail: [email protected]. ORCID

Guangwen Xu: 0000-0002-0025-3898 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by the National Basic Research Program of China (Grant 2014CB744305) and the National Natural Science Foundation of China (Grant U1302273).

■

REFERENCES

(1) Chew, K. J. The future of oil: Unconventional fossil fuels. Philos. Trans. R. Soc., A 2014, 372, 20120324. (2) Greene, D. L.; Hopson, J. L.; Li, J. Have we run out of oil yet? Oil peaking analysis from an optimizt’s perspective. Energy Policy 2006, 34, 515−531. (3) Tong, J.; Liu, J.; Han, X.; Wang, S.; Jiang, X. Characterization of nitrogen-containing species in Huadian shale oil by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Fuel 2013, 104, 365−371. (4) Landau, M. V.; Herskowitz, M.; Givoni, D.; Laichter, S.; Yitzhaki, D. Medium-severity hydrotreating and hydrocracking of Israeli shale oil. 1. Novel catalyst systems. Fuel 1996, 75, 858−866. (5) Hillier, J. L.; Fletcher, T. H.; Solum, M. S.; Pugmire, R. J. Characterization of macromolecular structure of pyrolysis products from a Colorado Green River oil shale. Ind. Eng. Chem. Res. 2013, 52, 15522−15532. (6) Yu, H.; Li, S.; Jin, G.; Tang, X. Hydrotreating of the diesel distillate from Huadian shale oil for production of clean fuel. J. Fuel Chem. Technol. (Beijing, China) 2010, 38, 297−301. (7) Oja, V. A breaf overview of motor fuels from shale oil of Kukersite. Oil Shale 2006, 23, 160−163. (8) Luik, H.; Luik, L.; Johannes, I.; Tiikma, L.; Vink, N.; Palu, V.; Bitjukov, M.; Tamvelius, H.; Krasulina, J.; Kruusement, K.; Nechaev, I. Upgrading of Estonian shale oil heavy residuum bituminous fraction by catalytic hydroconversion. Fuel Process. Technol. 2014, 124, 115− 122. (9) Yu, H.; Li, S.; Jin, G. Catalytic Hydrotreating of the Diesel Distillate from Fushun Shale Oil for the Production of Clean Fuel. Energy Fuels 2010, 24, 4419−4424. 1368


Article

Energy & Fuels (27) Zhang, T.; Zhang, L.; Zhou, Y.; Wei, Q.; Chung, K. H.; Zhao, S.; Xu, C.; Shi, Q. Transformation of Nitrogen Compounds in Deasphalted Oil Hydrotreating: Characterized by Electrospray Ionization Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2013, 27, 2952−2959. (28) Müller, H.; Andersson, J. T.; Schrader, W. Characterization of High-Molecular-Weight Sulfur-Containing Aromatics in Vacuum Residues Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Anal. Chem. 2005, 77, 2536−2543. (29) Lobodin, V. V.; Juyal, P.; McKenna, A. M.; Rodgers, R. P.; Marshall, A. G. Silver Cationization for Rapid Speciation of SulfurContaining Species in Crude Oils by Positive Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2014, 28, 447−452. (30) Liu, P.; Shi, Q.; Pan, N.; Zhang, Y.; Chung, K. H.; Zhao, S.; Xu, C. Distribution of Sulfides and Thiophenic Compounds in VGO Subfractions: Characterized by Positive-Ion Electrospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2011, 25, 3014−3020. (31) Purcell, J. M.; Juyal, P.; Kim, D.-G.; Rodgers, R. P.; Hendrickson, C. L.; Marshall, A. G. Sulfur Speciation in Petroleum: Atmospheric Pressure Photoionization or Chemical Derivatization and Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry. Energy Fuels 2007, 21, 2869−2874. (32) Tubaro, M.; Marotta, E.; Seraglia, R.; Traldi, P. Atmospheric pressure photoionization mechanisms. 2. The case of benzene and toluene. Rapid Commun. Mass Spectrom. 2003, 17, 2423−2429. (33) Hourani, N.; Muller, H.; Adam, F. M.; Panda, S. K.; Witt, M.; Al-Hajji, A. A.; Sarathy, S. M. Structural Level Characterization of Base Oils Using Advanced Analytical Techniques. Energy Fuels 2015, 29, 2962−2970. (34) Albiter, M.; Huirache-Acuna, R.; Paraguay-Delgado, F.; Rico, J.; Alonso-Nunez, G. Synthesis of MoS2 nanorods and their catalytic test in the HDS of dibenzothiophene. Nanotechnology 2006, 17, 3473− 3481. (35) Rabarihoela-Rakotovao, V.; Brunet, S.; Perot, G.; Diehl, F. Effect of H2S partial pressure on the HDS of dibenzothiophene and 4, 6dimethyldibenzothiophene over sulfided NiMoP/Al2O3 and CoMoP/ Al2O3 catalysts. Appl. Catal., A 2006, 306, 34−44. (36) Yu, K.; Li, H.; Watson, E. J.; Virkaitis, K. L.; Carpenter, G. B.; Sweigart, D. Models for Deep Hydrodesulfurization (HDS). Remote Activation of CS Bonds in Alkylated Benzothiophenes and Dibenzothiophenes by Metal Coordination to a Carbocyclic Ring. Organometallics 2001, 20, 3550−3559. (37) Kabe, T.; Ishihara, A.; Tajima, H. Hydrodesulfurization of sulfurcontaining polyaromatic compounds in light oil. Ind. Eng. Chem. Res. 1992, 31, 1577−1580. (38) Shiraishi, Y.; Tachibana, K.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 5. Denitrogenation reactivity of basic and neutral nitrogen compounds. Ind. Eng. Chem. Res. 2001, 40, 4919−4924. (39) Macaud, M.; Sévignon, M.; Favre-Réguillon, A.; Lemaire, M.; Schulz, E.; Vrinat, M. Novel methodology toward deep desulfurization of diesel feed based on the selective elimination of nitrogen compounds. Ind. Eng. Chem. Res. 2004, 43, 7843−7849. (40) Shiraishi, Y.; Tachibana, K.; Hirai, T.; Komasawa, I. A novel desulfurization process for fuel oils based on the formation and subsequent precipitation of S-alkylsulfonium salts. 3. Denitrogenation behavior of light oil feedstocks. Ind. Eng. Chem. Res. 2001, 40, 3390− 3397. (41) Ferdous, D.; Dalai, A.; Adjaye, J. Comparison of hydrodenitrogenation of model basic and nonbasic nitrogen species in a trickle bed reactor using commercial NiMo/Al2O3 Catalyst. Energy Fuels 2003, 17, 164−171. (42) Böhringer, W.; Schulz, H. Comparative Evaluation of Elemental Reactions in HDS-, HDO- and HDN-Reaction Networks of Model Compounds. Bull. Soc. Chim. Belg. 1991, 100, 831−840.

(43) Ancheyta, J.; Morales, P.; Betancourt, G.; Centeno, G.; Marroquín, G.; Muñoz, J. A. D. Individual Hydrotreating of FCC Feed Components. Energy Fuels 2004, 18, 1001−1004. (44) Koltai, T.; Macaud, M.; Guevara, A.; Schulz, E.; Lemaire, M.; Bacaud, R.; Vrinat, M. Comparative inhibiting effect of polycondensed aromatics and nitrogen compounds on the hydrodesulfurization of alkyldibenzothiophenes. Appl. Catal., A 2002, 231, 253−261. (45) Beltramone, A. R.; Resasco, D. E.; Alvarez, W. E.; Choudhary, T. V. Simultaneous Hydrogenation of Multiring Aromatic Compounds over NiMo Catalyst. Ind. Eng. Chem. Res. 2008, 47, 7161−7166.

1369


Understanding Shale Oil Hydrotreatment with Composition Analysis

Recommend Documents