Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen

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Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen-containing Compounds in the Hydrotreating Process of a Low Temperature Coal Tar Hongxing Ni, Chunming Xu, Rui Wang, Xiaofen Guo, Yinhua Long, Chao Ma, Lulu Yan, Xuxia Liu, and Quan Shi Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03659 • Publication Date (Web): 31 Jan 2018 Downloaded from http://pubs.acs.org on February 6, 2018

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Composition

and

Transformation

of

Sulfur-,

Oxygen-,

and

Nitrogen-containing Compounds in the Hydrotreating Process of a Low Temperature Coal Tar

Hongxing Ni,*†‡Chunming Xu‡, Ru Wang§, Xiaofen Guo§, Yinhua Long§, Chao Ma‡, LuLu Yan‡, Xuxia Liu‡, Quan Shi‡ †

Sinopec Research Institute of Petroleum Processing, Beijing 100083, China State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249,China § National Institute of Clean-and-Low-Carbon Energy, Beijing, 102209, China ‡

ABSTRACT: A low temperature coal tar was subject to a three-stage catalytic hydrotreating reactor. The raw coal tar and its hydrotreating products from each reactor section were characterized by electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The removal efficiencies of sulfur, nitrogen, and oxygen were 99.4%, 88.4%, and 78.1%, respectively. The molecular transformation routes of each heteroatomic species are different. Sulfur species were removed from low DBE (double bond equivalence) values to higher ones through the whole hydrotreating process. Furanic compounds and basic nitrogen compounds carried out the saturation of aromatic rings before the hydrogenation of low DBE species. Neutral nitrogen compounds were resistant in the processing and cannot be removed completely in the end of the hydroprocessing. The phenolic compounds were the most resistant to the hydrotreating during the whole process. The transformation capabilities of heteroatom compounds in the processing were as follows: phenolic compounds> neutral-nitrogen compounds > furanic compounds> basic-nitrogen compounds > sulfur compounds.

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1. INTRODUCTION In view of pollution from coal burning and petroleum depletion crisis, massive efforts were devoted to the clean utilization of coal and supplement to conventional liquid fuels. The annual yield of low temperature coal tar (LTCT), which produced as a byproduct of coal gasification and carbonization, has reached a huge value of about 20 million tons in China1. LTCT generally is a liquid fossil fuel which has many similar physical and chemical properties with petroleum and is considered as a potential alternative of crude oil. Since coal tar is a complex mixture composed of a plenty of heteroatoms, further hydrotreating processes are necessary2. Many studies were focused on the investigation of hydrogenation process technique and catalyst development for a deep hydrotreating of LTCTs. High operating temperature and pressure combined with low space velocities result in substantial reductions in oxygen, sulfur, and nitrogen contents3, 4. Bimetallic catalysts were the most commonly used catalysts, such as Co-Mo, Ni-Mo, and Ni-W. Co-Mo and Ni-Mo catalysts exhibited high hydrogenolysis capability for S, O, and N containing heteroatoms. For < 350 °C distillates, the sulfur compound is the most liable heteroatom species in the hydroprocessing and could be almost completely removed,2, 5, 6 while nitrogen and oxygen content can be reduced to less than 50 ppm.7, 8

A certain amount of nitrogen and oxygen was remained after the hydrogenation of a

raw LTCT9,

10

. The Ni-W catalyst showed a high hydro-cracking activity3 and

intermediate carbon number (C9–C16) selectivity7. These works reported the heteroatom content in the LTCT before and after hydrogenation process, and mainly focused on the removal ratio of heteroatoms. However, the molecular transformation of these heteroatom compounds in LTCTs during the hydrogenation process is still unclear. Gas chromatography-mass spectrometry (GC-MS), as well as two-dimensional GC-mass spectrometry (GC×GC-MS), were commonly used analysis methods for molecular characterization of coal tars. Based on the GC relevant analysis, phenols (especially alkyl phenols) were found as the predominant oxygen-containing species in the LTCT; other oxygen-containing compounds, such as ketones, dibenzofurans and carboxylic acids were also detected.11-14 Nitrogen-compounds were enriched in the basic fraction by acidic extraction and were primarily composed of quinolines, carbazoles, and acridinesas.15 In addition, a series of alkyl nitriles was identified in the neutral fraction from a LTCT.12 Sulfur-containing aromatics, such as thiophenes, benzothiophenes, and dibenzothiophenes with C0-C3 alkyl side chain were also detected in the coal tar.16, 17 Although GC separation enable the individual compound


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analysis, most heteroatom compounds cannot be eluted from the GC column due to their poor volatility and cannot be characterized by GC relevant techniques. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) possesses ultra high resolving power and high mass accuracy. Combining with electrospray ionization (ESI), FT-ICR MS has played a crucial role in the analysis of heteroatomic compounds in fossil fuels. Oxygen compounds with 1-6 oxygen atoms have been assigned from the FT-ICR MS analysis of a LTCT, among which the O1 (the class species has one oxygen atom in the molecules) and O2 are predominant and accounting for nearly 90% in relative abundance of the oxygen-containing compounds18. The O1 class species were most likely to be phenols with DBE value ranging from 4 to 26. The O2 class species were considered to be diphenols or monocarboxylic acids. Nitrogen-compounds revealed by FT-ICR MS were mainly composed of N1-3O0-5 class species. The N1 class species were the most abundant in the basic and neutral fractions with DBE values ranging from 4 to 20, while the N1O1 and N1O2 classes were dominated in the acid fraction.12, 19 Sulfur compounds with class species of S1O0–6 and S2O0–6 were identified by FT-ICR MS, which have broad DBE and carbon number distribution ranges from 0 to 20, and 10 to 40, respectively.20,

21

FT-ICR MS has significantly promoted the understanding of

molecular composition of LTCTs. In this work, a LTCT was hydrotreated in a three-stage reactor. The raw coal tar and its hydrotreating products from each reactor section were characterized by ESI FT-ICR MS. The aim of the study is to investigate the molecular composition and transformation selectivity of the catalytic hydrotreating for various heteroatoms in the LTCT. 2. EXPERIMENTAL SECTION 2.1. Materials A raw LTCT and its three hydrogenated products were obtained from the National Institute of Clean-and-Low-Carbon Energy. The hydrogenation reaction was carried out on a fixed bed reactor pilot plant. Three hydrogenation reactions were connected in series. The reactor was operated with a liquid hourly space velocity of 0.4 h-1, a volume to volume hydrogen-to-oil ratio of 1000, and a hydrogen pressure of 10 MPa. The Mo-Ni/Al2O3 was used as catalyst. The temperature of the three reactor sections were 280, 380, and 380 ºC, respectively. The products, HP1, HP2, and HP3 (corresponding to the three hydrogenation stages) were sampled after a 216 h continuous operation.


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Normal hexane (n-hexane), dichloromethane (DCM), and acetonitrile were purchased from the Beijing Reagent, Ltd. (Daxing District, Beijing, China) and further purified by distillation. Silver tetrafluoroborate (AgBF4) and methyl iodide (CH3I) were purchased from the J&K Chemical Ltd. and kept in dark, dry, low temperature environment. 2.2. Methylation The methylation reaction method of sulfur compounds was developed as described elsewhere22. In this work, it was applied to coal tar after optimizing its reagent quantity and reaction time. Briefly, a certain amount of oil (a total of 1, 1, 2, and 7 g for the raw coal tar, HP1, HP2, and HP3, respectively) was diluted to 20 mL with dichloromethane. Twenty five mol equivalent AgBF4 and 45 mol equivalent CH3I (based on the sulfur content in each tar oil) were added to each solution. Such obtained mixtures were stirring for 12 h at room temperature in dark. Then, repeated the procedure (adding agents and stirring for reaction) once to enhance the conversion. After the reaction, the product AgI was filtered and the sulfonium filtrate was subject to positive ion ESI FT-ICR MS analysis. In addition, the raw coal tar and three hydrogenated tars were analyzed by gas chromatography combined with sulfur chemiluminescence detector (GC-SCD), gas chromatography-flame ionization detector (GC-FID), and ESI FT-ICR MS. 2.3. GC−SCD Analysis. The GC-SCD analysis was performed with an Agilent 7890A. GC equipped with a HP-5 MS column (30 m × 0.25 mm × 0.25 µm) and a SCD detector (Agilent, 355). The column oven for four tars was initially kept at 80 °C for 1 min, followed by a ramp of 10 °C /min to 300 °C, then holding for 10 min. The injector and detector temperatures were held at 300 °C. Nitrogen was used as the carrier gas with a flow rate of 1 mL/min. 2.4. GC−FID Analysis. An Agilent 7890A GC−FID was used for the analysis of the coal tars. A HP-5 fused silica capillary column (30 m × 0.25 mm inner diameter × 0.25µm film thickness) was used. The oven was held at 50 °C for 5 min, then programmed to 300 °C at rate of 10 °C/min, and held at the final temperature for 5 min. The injector and detector temperatures were held at 300 °C. Nitrogen was used as the carrier gas with a flow rate of 1 mL/min.


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2.5. ESI FT-ICR MS Analysis. A Bruker Apex-ultra FT-ICR MS was used to analyze the four coal tars and methylated products. The instrument was equipped with a 9.4 T superconducting magnet (running at 9.0 T). The samples were first dissolved in toluene and then diluted by a mixture of toluene/methanol (1:3) to 0.2 mg/mL. The ESI source was operated in negative ion and positive ion modes respectively. The spray shield voltage was 3.5 kV, and the capillary column front and back end voltage was 4.0 kV and -320 V, respectively. The mass range was set at m/z 160–800. The data size was set to 4 M words. A total of 128 scans of FT-ICR data sets were accumulated to enhance the signal-to-noise ratio and dynamic range. Methodologies for FT-ICR MS mass calibration, data acquisition, and processing were described elsewhere.23, 24 3. RESULTS AND DISCUSSION 3.1. Removal Efficiency of Heteroatoms in the Hydrotreating Process. The element content of sulfur, nitrogen, oxygen of the coal tar and its three hydrotreating products were shown in Figure 1. In the coal tar, the contents of S, N, and O were 2130 wppm, 9360 wppm, and 8.71wt%, respectively. Sulfur content was the lowest, near a quarter of nitrogen content. Oxygen was the most abundant heteroatom and was about 8 times more than nitrogen in content. All these heteroatom contents decreased stage by stage. Sulfur content changed from 2130 wppm to 1580 wppm, 860 wppm, and 12.5 wppm after each stage, respectively. Totally 99.4% of sulfur was removed in the hydrotreating. Meanwhile, 88.4% of nitrogen and 78.1% of oxygen were removed. Thus, in terms of total removal ratio, the hydro-deheteroatom capability follows the order of S>N>O. Furthermore, comparing three hydrotreating stages, these heteroatoms showed a different removal pattern. Approximate equivalent quantity of sulfur was removed in each stage. Nitrogen was mainly removed at the second and the third stages, while oxygen was mostly removed at the third hydrogenation stage. The hydrotreating process conditions for the three hydrogenation states were designed as pre-, slight-, and deep-hydrotreating stages, the easy-to-remove heteroatoms prefer to hydrogenolysis

at prior stages and vice versa.

Therefore, the content change during three hydrotreating stages also indicates that the hydro-removal capability follows the order of S>N>O. 3.2. Sulfur-containing Compounds Figure 2 shows the gas chromatograms of the raw coal tar and its three


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hydrotreating products detected by GC-SCD. In the raw coal tar, most abundant peaks presented in the chromatogram at early retention time (before 20 minute) were corresponding to thiophenes and benzothiophenes. After the first hydrotreating stage, several peaks at early retention time in HP1 chromatogram were receded, which indicates that some small sulfur-compound molecules, like thiophenes were partially removed. Meanwhile, a hump is presented in the HP1 chromatogram, indicates that the composition of sulfur compounds in HP1 is still very complex. In contrast, HP2 has a simple chromatogram which showing three peaks corresponding to S4, S6, and S8, respectively. Most GC-SCD detectable sulfur-containing compounds like dibenzothiophenes were removed in the second hydrotreating stage. However, elemental analysis indicates that the sulfur content of HP2 was still as high as 860 ppm. The high sulfur content should be attributed to the dissolution of elemental sulfur in HP2 and/or sulfur compounds cannot be eluted from the GC column. Sulfur-containing compounds were characterized by positive ion ESI FT-ICR MS after methylation. The compound distributions were displayed as double bond equivalence (DBE) versus carbon number derived from molecular formula, as shown in Figure 3. In the raw coal tar, the S1 class species (molecules with one sulfur atom) distributed in a wide range of DBE (0-22) and carbon number (14-47) with the distribution center at 9-15 and 20-30, respectively. The S1 class species in HP1 has similar distribution with the raw coal tar, but most of the low DBE components (less than 6) were disappeared after the hydrotreating. In HP2, components with DBE less than 9 were completely removed; compounds with high DBE values and large carbon number show high relative abundance. No sulfur-compound was detected in HP3 which was consistent with the result of GC-SCD analysis. A series of DBE=0 is more likely thols (mercaptans) because thioethers (sulfides) cannot survive under the high temperature of the hydrogenation process. DBE values of 3, 6, and 9 should be thiophenes, benzothiophenes and dibenzothiophenes, respectively22. Figure 2 and 3 indicates that hydro-desulfurization process was carried out from low condensation degree molecules to high ones. All the mercaptanes and most thiophenes were firstly removed in the first hydrogenation stage, followed by the remaining thiophenes (DBE=3) and the benzothiophenes in the second stage. After the third hydrogenation stage, dibenzothiophenes and highly condensed compositions were completely removed. Thus, the liability of the sulfur compounds in the hydrotreating process can be in the order of mercaptanes/thioethers > thiophenes > benzothiophenes > dibenzothiophenes and more condensed constitutions. Unlike the


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study of standard model sulfur compounds, the saturation of aromatic rings was not observed.25, 26 Therefore, the hydro-desulfurization in the coal tar can be assumed to a direct hydrogenolysis procedure. 3.3. Phenolic Compounds Oxygen-compounds generally are the most abundant heteroatom compounds in LTCTs, as well as other coal derived liquids.27 The Ox (x=1-7), N1Ox (x=1-6), and N2Ox (x=1-4) class species were assigned from negative ion ESI FT-ICR mass spectrum of the raw coal tar and the relative abundance of these compounds were shown in Figure S1 (see Supporting Information). Along with the hydrotreating process, the upper limits of oxygen number decreased stage by stage. Figure 4 shows the iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrotreating products. The distribution patterns of the four coal tars in Figure 4 are roughly similar with each other, which showing DBE value and carbon number range of 4-23 and 12-40, respectively. Compounds with DBE value between 9 and 16 were dominant and high carbon compounds with DBE=4, which should be alkyl phenols18, were abundant in all the four coal tars. It should be noted that the plots shown in Figure 4 of the raw coal tar and HP1 were almost identical, which indicates that there was no/negligible hydrogenation reaction occurred on the phenolic compounds in the first hydrogenation stage. This result is consistent with that of GC-FID shown in Figure S2 (see Supporting Information). From HP1 to HP3, DBE values of the most abundant species shift from 12 and13 to 9 and10. There are two explanations for the DBE changes. One is the transformation of multi-hydroxy compounds11,

18

to mono-hydric phenols, which

leaded to a relative abundance change. The other is the saturation of aromatic rings.6, 28

However, the 3-DBE decline implies the later should be the main process in

hydrogenation stage 2 and 3. After the final hydrotreating stage, the DBE distribution was 4 to 23, similar to the raw coal tar. This is consistent with the understanding of that phenolic compounds are hard to be hydrogenated due to the high activation energy of phenolic C-O bond.29, 30 3.4. Furanic Compounds Furanic compounds are highly refractory oxygenated chemical groups and abundant in coal tar.31 Furanic compounds can be ionized after methylation and further analyzed by positive ion ESI FT-ICR MS (see Figure S3 in Supporting


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Information). Figure 5 shows the iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrogenated coal tars. The O1 class species was considered as furanic compounds, which has a wide range of carbon number (15-54) and DBE value (3-29) in the raw coal tar. The distribution center is at about 20-40 carbons and 7-23 DBEs. After the first hydrogenation stage, the shrinkage in DBE distribution range of abundant compounds was obviously. Furanic compounds could be hydrogenated and resulted in a downward movement of DBEs. Compounds with low DBE value like alkyl furans (DBE=3) were partially removed in the second stage and were completely removed in the third stage. It implies that the furanic compounds with low condensation degree are more likely to be hydro-removed than those of high condensation degree. Although furanic and phenolic compounds both belong to the oxygen-compounds, their transformation route is different. The conversion of furanic compounds was similar to sulfur-compounds, but was more resistant. 3.5. Neutral Nitrogen Compounds Figure 6 shows the DBE and carbon number distribution of N1 class species assigned from the negative ion ESI FT-ICR mass spectra, which corresponding to neutral nitrogen compounds.32 The raw coal tar has a wide range of DBE values (9-18) and carbon numbers (16-29), similar to that of HP1. After the second hydrotreating stage, new compounds were generated leading to the lower limit of DBE value decreased to 6. This lower limit was remained to the final hydrotreating product. Through the hydrotreating process, the DBE value of the most abundant compounds decreased gradually from 15 in the raw coal tar to 13 in HP2, and further to 10 in HP3. In the first hydrotreating stage, the slight relative abundance enhancement of compounds at DBE=13 and 14 implies hydrogenation reaction was occurred on the neutral nitrogen compounds. While, in the second hydrotreating stage, The DBE value declined from 9 to 6 distinctly indicates that one aromatic ring was saturated, as carbazoles (DBE=9) transformed to indols (DBE=6). As well, the DBE value shift of most abundant species from 15 to 13 could be tetra-hydrogenation of naphthalene structures. We speculate that the hydrogenolysis of neutral nitrogen compounds was mainly occurred from the second hydrotreating stage and accompanied with the generation of low DBE compounds. Similar to the phenolic compounds, distribution pattern changes of neutral nitrogen compounds were not distinct.


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3.6. Basic Nitrogen Compounds The changes of basic nitrogen content were specific along the hydrotreating. Basic nitrogen contents of the coal tar and its hydrotreating products were 3805 wppm, 4103 wppm, 3354 wppm, and 197 wppm, respectively. The increasement of basic nitrogen in HP1 indicates the generation of basic nitrogen compounds in the hydrotreating. Basic nitrogen compounds can be characterized by positive ion ESI FT-ICR MS.32 Figure 7 shows the DBE and carbon number distribution of N1 class species of basic nitrogen compounds. The DBE values and carbon numbers of the raw coal tar were at the ranges of 4-23 and 14-50, respectively. Abundant compounds series with 4 and 5 DBEs and a carbon number range of 24-38 indicates the dominant of large molecular pyridinic compounds. In HP1, the relative abundance of compounds with DBE=4 and 5 were sharply reduced, meanwhile, compounds with DBE values of 1-3 appeared. This indicates the saturation of aromatic rings was occurred and most pyridines were transferred to amines. These compounds were largely decreased in HP2 and HP3, implying the produced amines were not stable for the hydrotreating. Compared to the neutral nitrogen compounds, the basic nitrogen compounds in HP3 had a wide DBE range of 6-13 rather than several specific DBE value like 10 and 13 in the neutral nitrogen compounds. It implies that more molecular structures of basic nitrogen compounds are hard to be hydrogenated. In the whole process, no aliphatic amines (DBE=0) were observed, which indicated that aliphatic amines were not stable to exist in the hydrotreating process. 4. SUMMARY Sulfur, nitrogen, and oxygen compounds in the raw coal tar and three-stage hydrogenation products were subject to FT-ICR MS and GC-SCD analysis. The hydro-removal ratio of sulfur, nitrogen, and oxygen were 99.4%, 88.4%, and 78.1%, respectively. The catalyst and the operation conditions were optimized for desulfuration, as expected, the conversion of sulfur compounds in the hydrotreating were the most effective. Furanic and basic nitrogen compounds both exhibited saturation of aromatic rings first, and then the removal of heteroatoms was observed. Neutral nitrogen and phenolic oxygen compounds were more resistant for hydrogenolysis than others and showed prefer to saturate aromatic rings. The investigated compounds show a hydrogenation resistance order of phenolic > neutral-nitrogen > furanic > basic-nitrogen > sulfur compounds. We cannot obtain a quantitative result in molecular composition. However, the results should be valuable


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for the understanding of the transformation mechanism of heteroatoms in the coal tar hydrotreating. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] ACKNOWLEDGMENTS This work was supported by the National High Technology Research and Development Program 863 (2011AA05A202) and the National Natural Science Foundation of China (NSFC 21236009, and 21376262). REFERENCE 1.

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chromatography–mass spectrometry and electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry. Energy & Fuels 2012, 26, (6), 3424-3431. 13. Alhassan, A.; Andersson, J. T., Ketones in Fossil Materials  A Mass Spectrometric Analysis of a Crude Oil and a Coal Tar. Energy & Fuels 2013, 27, (10), 5770-5778. 14. Omais, B.; Courtiade, M.; Charon, N.; Thiébaut, D.; Quignard, A.; Hennion, M.-C., Investigating comprehensive two-dimensional gas chromatography conditions to optimize the separation of oxygenated compounds in a direct coal liquefaction middle distillate. Journal of Chromatography A 2011, 1218, (21), 3233-3240. 15. Granda, M.; Menéndez, R.; Moinelo, S. R.; Bermejo, J.; Snape, C. E., Mass spectrometric characterization of polynuclear aromatic nitrogen compounds in coal tar pitches separated by extrography. Fuel 1993, 72, (1), 19-23. 16. Mössner, S. G.; Wise, S. A., Determination of polycyclic aromatic sulfur heterocycles in fossil fuel-related samples. Analytical chemistry 1999, 71, (1), 58-69. 17. Machado, M. E.; Fontanive, F. C.; de Oliveira, J. V.; Caramão, E. B.; Zini, C. A., Identification of organic sulfur compounds in coal bitumen obtained by different extraction techniques using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection. Analytical and bioanalytical chemistry 2011, 401, (8), 2433-2444. 18. Shi, Q.; Pan, N.; Long, H.; Cui, D.; Guo, X.; Long, Y.; Chung, K. H.; Zhao, S.; Xu, C.; Hsu, C. S., Characterization of middle-temperature gasification coal tar. Part 3: Molecular composition of acidic compounds. Energy & Fuels 2012, 27, (1), 108-117. 19. Pan, N.; Cui, D.; Li, R.; Shi, Q.; Chung, K. H.; Long, H.; Li, Y.; Zhang, Y.; Zhao, S.; Xu, C., Characterization of middle-temperature gasification coal tar. Part 1: Bulk properties and molecular compositions of distillates and basic fractions. Energy & Fuels 2012, 26, (9), 5719-5728. 20. Rathsack, P.; Kroll, M. M.; Otto, M., Analysis of high molecular compounds in pyrolysis liquids from a german brown coal by FT-ICR-MS. Fuel 2014, 115, 461-468. 21. Rathsack, P.; Otto, M., Classification of chemical compound classes in slow pyrolysis liquids from brown coal using comprehensive gas-chromatography mass-spectrometry. Fuel 2014, 116, 841-849. 22. Wang, M.; Zhao, S.; Chung, K. H.; Xu, C.; Shi, Q., Approach for selective separation of thiophenic and sulfidic sulfur compounds from petroleum by methylation/demethylation. Analytical chemistry 2015, 87, (2), 1083-1088. 23. Shi, Q.; Hou, D.; Chung, K. H.; Xu, C.; Zhao, S.; Zhang, Y., Characterization of heteroatom compounds in a crude oil and its saturates, aromatics, resins, and asphaltenes (SARA) and non-basic nitrogen fractions analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Energy & Fuels 2010, 24, (4), 2545-2553. 24. Ni, H.; Hsu, C. S.; Lee, P.; Wright, J.; Chen, R.; Xu, C.; Shi, Q., Supercritical carbon dioxide extraction of petroleum on kieselguhr. Fuel 2015, 141, 74-81. 25. Aubert, C.; Durand, R.; Geneste, P.; Moreau, C., Hydroprocessing of dibenzothiophene, phenothiazine, phenoxathiin, thianthrene, and thioxanthene on a sulfided NiO  MoO3γ-Al2O3 catalyst. Journal of Catalysis 1986, 97, (1), 169-176. 26. Fang, M.; Tang, W.; Yu, C.; Xia, L.; Xia, Z.; Wang, Q.; Luo, Z., Performance of Ni-rich bimetallic phosphides

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Figure 1. Heteroatom content of the raw coal tar (CT) and three hydrotreating products (HP1, HP2 and HP3). Figure 2.GC-SCD chromatograms of the raw coal tar, HP1, HP2, and HP3. Vertical scales were initialized by the identical intensity. Figure 3.Iso-abundance plots of DBE versus carbon number of S1 class species in the raw coal tar and three hydrogenation products detected by positive ion ESI FT-ICR MS. Figure 4.Iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrotreating products detected by negative ion ESI FT-ICR MS. Figure 5.Iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrotreating products assigned from positive ion ESI FT-ICR mass spectra of the methylation products. Figure 6.Iso-abundance plots of DBE versus carbon number of N1 class species in the raw coal tar and three hydrogenated coal tars detected by negative ion ESI FT-ICR MS. Figure 7.Iso-abundance plots of DBE versus carbon number of N1 class species in the raw coal tar and three hydrogenated coal tars detected by positive ion ESI FT-ICR MS.


Page 13 of 19

100

2130

8.71

9360

CT HP1 HP2 HP3 Basic nitrogen

7990 6.86

Removal rate（%）

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

1580 5.34

99.4%

88.4%

4650

50

78.1%

4103

860

3805 3354

1.91 1090

0

12.5

S (wppm)

197

N (wppm)

O (wt%)

Figure 1. Heteroatom content of the raw coal tar (CT) and three hydrotreating products (HP1, HP2 and HP3).


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

Page 14 of 19

CT

C1-BT C2-BT

HP1

DBT

C3-BT

BT S8

HP2

S4

S6

HP3

8

10

12

14

16

18

20

22 24 Time (min)

26

28

30

32

34

36

38

Figure 2.GC-SCD chromatograms of the raw coal tar, HP1, HP2, and HP3. Vertical scales were initialized by the identical intensity.


Page 15 of 19

+ESI

S1 25

25

DBE

CT

HP1

20

20

15

15

10

10

R S R

5

5

0

0

R

10 25

20

40

30

S

S

SH

50 10 25

20

30

40

50

30

40

50

HP2

HP3 20

20

15

15

not detected

DBE

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

10

5

5

0

0 10

20

40

30

50 10

Carbon number

20

Carbon number

Figure 3.Iso-abundance plots of DBE versus carbon number of S1 class species in the raw coal tar and three hydrogenation products detected by positive ion ESI FT-ICR MS.


Energy & Fuels

-ESI 25

O1 25

CT

HP1

DBE=12 20

20

OH

DBE

R

15

15

10

10 OH

5

5 R

0

0 10

20

30

40

25

10 25

HP3 DBE=9

20

20

30

40

20

30

40

HP2

20 OH

R

DBE

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

Page 16 of 19

15

15

10

10

5

5

0 10

20

30

Carbon number

40

0 10

Carbon number

Figure 4.Iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrotreating products detected by negative ion ESI FT-ICR MS.


Page 17 of 19

+ESI 30

O1-Me 30

CT

25

20

20

15

15

10

10

DBE

25

5

HP1

R furan 5 O

0 10 30

20

40

30

50

0 10

60 30

25

20

20

15

15

10

20

30

40

50

60

30

40

50

60

HP2

HP3 25

DBE

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

O dibenzofuran 10

R

5

O

R

benzofuran 5

0

0 10

20

30

40

50

60

10

20

Carbon number

Carbon number

Figure 5.Iso-abundance plots of DBE versus carbon number of O1 class species in the raw coal tar and three hydrotreating products assigned from positive ion ESI FT-ICR mass spectra of the methylation products.


Energy & Fuels

-ESI

DBE

30

N1 30

CT

25

25

20

20

HP1 R

dibenzocarbazole 15 benzocarbazole

15

carbazole

10

5

N H

0 10 30

20

0 40 10 30

30

N H

10

R

5

DBE

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

Page 18 of 19

HP3

25

25

20

20

20

30

40

30

40

HP2 R

N

H 15 tetrahydro-dibenzocarbazole

15

tetrahydro-benzocarbazole 10

10

indole 5

R N H

0 10

20

30

5

0 40 10

Carbon number

20

Carbon number

Figure 6.Iso-abundance plots of DBE versus carbon number of N1 class species in the raw coal tar and three hydrogenated coal tars detected by negative ion ESI FT-ICR MS.


Page 19 of 19

+ESI 30

N1 30

CT

25

20

20

15

15

10

10

5

5

DBE

25

0 30

10

20

0

R

20

20

15

15

10

10

5

5

0 10

20

40

30

30

40

50

25

N H

N

20

HP2

R

25

HP1

50 10 30

40

30

HP3

DBE

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

0 50 10

Carbon number

20

30

Carbon number

40

50

Figure 7.Iso-abundance plots of DBE versus carbon number of N1 class species in the raw coal tar and three hydrogenated coal tars detected by positive ion ESI FT-ICR MS.


Composition and Transformation of Sulfur-, Oxygen-, and Nitrogen

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