Thermoplastic Properties of Coal and Coal Extract - Energy & Fuels

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Thermoplastic Properties of Coal and Coal Extract Chia-Ching Chu, Chih-Min Chang, Der-Her Wang, and Thou-Jen Whang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b02327 • Publication Date (Web): 02 Oct 2017 Downloaded from http://pubs.acs.org on October 7, 2017

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Thermoplastic Properties of Coal and Coal Extract Chia-Ching Chu,† Chih-Min Chang,† Der-Her Wang,‡ and Thou-Jen Whang*,† † ‡

Department of Chemistry, National Cheng Kung University, Tainan 70101, Taiwan Steel Research Department, China Steel Corporation, Kaohsiung 81233, Taiwan

Abstract The aim of this study is to find a simple, effective and non-destructive way to estimate the fluidity of coal. Three kinds of metallurgical coals were blended in a specific ratio for fluidity measurement by a Gieseler plastometer and coke strength by the Roga test. One of the metallurgical coals was extracted with four kinds of solvents. The solvent-extracted extracts were further undergone heat treatment at different temperatures and then added to the blended coal to examine the change of fluidity and coke strength. Both of the heat-treated and untreated coal extracts were further investigated by elemental analysis, thermogravimetric analysis, solid-state 13C nuclear magnetic resonance, and X-ray diffractometry, and it was found that the heat treatment will increase the degree of graphitization. The aromatic carbon content was found to correlate significantly with the fluidity of coal, and the relationship among the ratio of aromatic carbon to aliphatic carbon, aromaticity, and fluidity was studied in this work. Finally, X-ray diffractometry is suggested to be a non-destructive method to estimate the fluidity of coal.

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1. INTRODUCTION

Coal is primarily composed of the macromolecular structure of polycyclic aromatic hydrocarbons (PAHs) with some hetero-atom groups and admixes with a trace amount of mineral matters.1 Its secondary network structure is derived from aromatic ring stacking, aliphatic side-chain entanglement, hydrogen bonding, cation bridges, and electron donor-acceptor interaction. The aggregation of the coal structure is believed to be correlated closely with coal ranks, which is governed by the noncovalent bonding interactions, such as a complicated network structure. Polar solvents containing nitrogen or oxygen (for example, amine, phenol, pyridine, tetrahydrofuran, and dimethylformamide etc.) can be used to extract raw coal, and the network structure of coal has been widely investigated by means of solvent extraction method. Besides, polar solvents have been proven to be effective for liberating the noncovalent bonding interactions from the network structure of coal.2

There are several methods for studying the structure and composition of coal including destructive methods, e.g., elemental analysis and thermogravimetric analysis, and non-destructive methods, e.g., nuclear magnetic resonance (NMR) and X-ray diffraction spectroscopy. Solid-state 13C NMR (13C SSNMR) is a powerful instrument and technique which enables us to investigate coal structure without destruction of coal sample and to measure carbon aromaticity (fa) as well as the fraction of aromatic carbon to aliphatic carbon.2-6 The chemical shift of SSNMR can also be simulated by theoretical calculation which involves the structural information, and the simulation results are used to modify the chemical structure model of coal or coal extract.7,8 X-ray diffraction (XRD) is also a non-destructive technique which has been used to characterize carbonaceous materials for decades. Coal is a typical example of the carbonaceous material and its structure information can 2 ACS Paragon Plus Environment

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be obtained by XRD for a better understanding of coal chemistry. In general, the X-ray diffractogram of coal shows broad and diffuse peaks since coal has a heterogeneous and amorphous structure. Moreover, coal has similar XRD peak positions as graphite which has sharp and clear XRD peaks; that is to say, coal has an intermediate structure between the graphite and the amorphous carbonaceous material, and the XRD peaks become sharper and less diffuse with the increase of coal rank.9 The classification of the carbon-related peaks at approximately 2θ = 20° and 26°, viz. γ-band and π-band respectively, can be analyzed by XRD in slow step scan mode. The γ-band is believed to be due to aliphatic chains and the π-band is due to aromatic carbons.10

In this study, a slightly-caking coal (which is later denoted as Coal-III) was extracted with four kinds of solvents and the solvent-extracted extracts were then further examined by elemental analysis to identify the variation of carbon and hydrogen contents. A Gieseler plastometer was used to measure the fluidity of the coal samples with the addition of the coal extract, and the coke strength of these coal samples was also determined by the Roga test. The fluidity of coal can be estimated by the crucible swelling number (CSN) analysis. However, in contrast to the CSN analysis, the XRD is a non-destructive method and it could avoid personal subjective judgment of the shape of coke. In order to establish a simple and non-destructive method to estimate the approximate fluidity of coal, both of the XRD and SSNMR techniques were introduced into this study to explore the relationship among the ratio of aromatic carbon to aliphatic carbon (CAr/CAl), aromaticity (fa value), and fluidity. It was found that CAr/CAl and fa value have a negative relationship with fluidity, and the aromatic carbon content and aliphatic carbon content can be determined by XRD method. Therefore, the XRD is suggested to be a simple, effective and nondestructive way to estimate the fluidity of coal.


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2. EXPERIMENT

2.1. Sample Preparation. Three kinds of metallurgical coals supplied by China Steel Corporation (CSC) were selected for this study. A high-volatile bituminous caking coal, a lowvolatile bituminous caking coal, and a high-volatile bituminous slightly-caking coal are denoted as Coal-I, Coal-II, and Coal-III, respectively. Elemental analysis (EA) was carried out using an elemental analyzer (Elementar vario EL III, Hanau, Germany). The analysis of the three raw coals is summarized in Table 1.11 A standard coal blend (SCB), which is composed of 35 wt% Coal-I, 40 wt% Coal-II, and 25 wt% Coal-III, was prepared for the thermoplastic test and the Roga test.12

2.2. Solvents and Extraction Procedure. N-methyl-2-pyrrolidinone (NMP), quinoline (QN), a 1:1 (by volume) mixture of N-methyl-2-pyrrolidinone and quinoline (NMP/QN), and coal-tar creosote oil (CCO) were separately used as extraction solvents. The coal-tar creosote oil was provided by CSC and was obtained from the fraction of the coal-tar distillation.

Coal-III was extracted with different solvents by the following procedure: 50 g of the coal sample and 250 g of the extraction solvent were placed into a round-bottom flask equipped with a reflux condenser. Thermal extraction was carried out using a heating mantle at 360°C for 3 h under an inert nitrogen atmosphere. After extraction, the coal component was precipitated by adding an excess amount of n-hexane into the extract mixture.13 The mixture was then filtered and washed with dichloromethane. The extraction solvent was subsequently removed by using the vacuum distillation method, and then the rest of the pitch-like extract was dried in vacuo at 200°C for 6 h. The glass-like dried extract was then scraped and gathered from the flask and was prepared for 4 ACS Paragon Plus Environment

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further investigation.14 A portion of the coal extract was further heated at a specific temperature for around 30 min, which is called preheating treatment, to eliminate interference such as aliphatic compounds and remaining solvents.

2.3. Thermogravimetric Analysis. The coal extract sample was tested by using a thermogravimetric analyzer (TA Instruments Q500, New Castle, DE, USA). The sample was placed on a platinum sample holder and was heated under an inert gas flow (40 mL/min nitrogen) from 40 to 800°C with 30 °C/min temperature ramp.

2.4. Thermoplasticity. The thermoplastic properties were measured using a Gieseler plastometer (R. B. Automazione s.r.l. Plastometer PL 2000, Genova, Italy) in a temperature range from 300 to 550°C with a temperature ramp of 3 °C/min and recorded the fluidity in dial divisions per minute (ddpm).

2.5. Roga Index – Determination of Caking Power. The Roga index (R.I.) indicates the caking properties of the coal sample under standard conditions. A fixed amount of standard anthracite is mixed carefully with the coal sample and then heated up to 850°C for 15 min. After cooling, the produced coke is screened and tested for mechanical strength by treating the coke in a tumbling drum at a specific time, which is called the abrasion test. The Roga index can be calculated from the test results; the higher the remaining coke, the higher the Roga index. The Roga test is described in detail elsewhere.12,15

2.6. Solid-State 13C Nuclear Magnetic Resonance. The solid-state 13C-NMR measurements were carried out at 100 MHz on a Bruker Avance 400 NMR spectrometer (Bruker BioSpin GmbH, Rheinstetten, Germany) with magic angle spinning (MAS) at 5 kHz. The measurements were 5 ACS Paragon Plus Environment

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performed under the following conditions: typically 2000–4000 scans were accumulated for the single pulse excitation technique with a relaxation delay of 5 s and a 90° 13C pulse of 5.5 μs.

2.7. X-ray Diffractometry. An X-ray powder diffractometer (Shimadzu XRD-6100, Kyoto, Japan) was used to carry out the slow step scan XRD analysis. The powder coal samples were placed on an aluminum sample holder and analyzed using Cu Kα (40 kV, 30 mA) radiation with a Bragg-Brentano optical system. The scan was performed in the 2θ range of 15–70° with a scanning speed of 0.02° /step and a counting time of 2 seconds at each step.

3. RESULTS AND DISCUSSION

3.1. Elemental analysis of the coal extract. The results of EA are shown in Table 2, which indicates that the hydrogen content in each sample decreases as the preheating treatment temperature increases. In general, the bond strength of the aliphatic hydrocarbons (C−H) is weaker than that of the aromatic hydrocarbons (Ar−H); therefore, the aliphatic C−H bonds will be broken easier as the temperature increases, which results in a reduction of the hydrogen content.

The carbon to oxygen ratio (C/O) does not vary as much as the carbon to hydrogen ratio (C/H) under various preheating treatment temperatures. The decrease of carbon content suggests that a portion of the carbon atoms react with atmospheric oxygen to form carbon dioxide (CO2). The carbon content varies with different preheating treatment temperatures because higher treatment temperature results in the decrease of hydrogen content and thus the increase of carbon content. Therefore, the relative increase of carbon content implies that the decrease of the hydrogen content


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of the coal extract. The C/H ratio shows obviously increasing trend when the preheating treatment temperature is increasing; moreover, a sudden increase of the C/H ratio is observed when the preheating treatment temperature is higher than 300°C, which indicates that a significant breaking of the aliphatic C−H bonds takes place at this temperature.

3.2. Thermogravimetric analysis. Coal-III extract extracted with different solvents was analyzed using thermogravimetric analysis (TGA), as shown in Fig. 1(a). The QN-extracted extract has more residual material than the other extracts, and the pyrolysis apparently appears to occur at approximately 450°C, which implies that the QN-extracted extract contains more of the highmolecular-weight material than the others.16

The NMP-extracted extract after the preheating treatment was also analyzed using TGA, as shown in Fig. 1(b). The numeric value after the solvent abbreviation (e.g. NMP-150) represents the preheating treatment temperature of the coal extract. The weight loss of the coal extract decreases with increasing preheating treatment temperature, which indicates that the lowmolecular-weight materials are removed from the coal extract during the preheating treatment. The coal extract treated at higher temperature leads to lower weight loss in the TGA analysis, which means that the high-temperature-treated coal extract has a higher residual of the high-molecularweight materials.

3.3. Thermoplasticity measurement. Thermoplastic properties of the SCB and the SCB with a 5 wt% addition of Coal-III extract extracted with different solvents are shown in Fig. 2(a). The increasing fluidity of the SCB with an addition of NMP-extracted extract suggests that the NMP is a highly polar solvent which can readily extract coal organic species from coal material during the thermal extraction process.17,18 These coal organic species extracted with NMP are believed to 7 ACS Paragon Plus Environment

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act as a lubricant in the coal structure so that the fluidity increases.

CCO is mainly composed of PAHs, which contains catacondensed benzenoids (e.g. naphthalene and 1-methylnaphthalene) and pericondensed benzenoids (e.g. phenanthrene and acenaphthene), and a minor amount of polar substances (e.g. quinoline) so that it also has an excellent extraction ability. In addition, a plenty amount of the aromatic coal organic species which were extracted with CCO (see Table 3) can readily condense into the coal structure. Thus, the SCB with an addition of the CCO-extracted extract shows lower fluidity than that with an addition of the NMPextracted extract.

The thermoplastic property of the SCB with an addition of QN-extracted extract shows different behavior in comparison to those with an addition of extract extracted with NMP or CCO. QN is a heterocyclic organic compound which has similar polarity to NMP. It can be an effective solvent for coal extraction because of the ability to relax the network structure or entangling structure of coal at high temperature.16 Therefore, the QN-extracted extract has a large amount of coal organic species so that adding it to the SCB exhibits excellent fluidity.

The QN-extracted extracts after the preheating treatment were added to the SCB as well, which were analyzed by Gieseler plastometer as shown in Fig. 2(b). The fluidity of the SCB increases with the addition of the coal extracts; however, the fluidity decreases with the increase of preheating treatment temperature because of the pyrolysis of organic matter or the evaporation of low-molecular-weight species. The extract after the heat treatment which has a higher degree of graphitization exhibits lower ability to improve the fluidity of coal.

3.4. The effect of an addition of coal extract on coke strength. Coke strength can be enhanced 8 ACS Paragon Plus Environment

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by adding coal extracts, as described in detail elsewhere.11 The enhancement of coke strength is proportional to the fluidity of coal extract since the high-fluidity materials have a wider temperature range of thermoplasticity which acts as the solvent-like liquid substances and blends well with the coal. The occurrence of condensation and polymerization during the hightemperature treatment is important for strengthening the coke strength.19,20 To elucidate the relationship between the coke strength and the thermoplasticity, the extract extracted with QN or CCO after the preheating treatment at different temperatures was added to the SCB, respectively, as shown in Fig. 3. The coke strength decreases with the increase of preheating treatment temperature of the coal extract owing to the elimination of high-fluidity materials during the preheating treatment; in addition, as mentioned in the previous section, the heat-treated extract has a higher degree of graphitization and, therefore, exhibits lower ability to condense with coal.

3.5. Solid-state

13C

nuclear magnetic resonance analysis. With respect to the 13C SSNMR

spectra of coal, the chemical shifts represent different functional groups.7,21,22 The chemical shift interval of 0–65 ppm represents aliphatic carbon, which can be approximately subdivided into three intervals: (1) 0–25 ppm represents the methyl carbon (−CH3); (2) 25–35 ppm represents the methylene carbon of linear alkyl chain or cycloalkane (−CH2−)n; (3) 35–65 ppm represents more complex aliphatic structures such as aliphatic carbon connected to oxygen (−OCH3, −O−CH2−) and nitrogenated carbon. The chemical shift interval of 100–160 ppm represents aromatic carbon, which can be roughly subdivided into three intervals: (1) 100–120 ppm represents the protonated aromatic carbon; (2) 120–145 ppm represents the quaternary aromatic carbon; (3) 145–160 ppm represents the aromatic carbon connected to oxygen (Ar−O).

The

13

C SSNMR integrated intensities of NMP-extracted extract with treating at preheating 9 ACS Paragon Plus Environment

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treatment temperatures of 150, 300, 450 and 600°C are shown in Table 3. The aromaticity (fa value) is defined as the intensity ratio of aromatic carbon to total carbon, which is fa = CAr/(CAr + CAl).23,24 Both of the fa value and the ratio of aromatic carbon to aliphatic carbon (CAr/CAl) increase with the increase of preheating treatment temperature. Fig. 4 illustrates the relationship between CAr/CAl ratio and fa value of the NMP-extracted extract after the preheating treatment. The fa value shows a positive correlation with the CAr/CAl ratio, which reveals that the degree of graphitization of the coal extract increases with the increase of preheating treatment temperature. The chemical shift interval of 120–145 ppm shows an obvious increase of the quaternary aromatic carbon, which means that the PAHs become the main structure of the coal extract. Four kinds of the coal extracts, which were extracted with NMP, QN, NMP/QN, and CCO, respectively, were further investigated by 13C SSNMR as shown in Table 3. The CCO-extracted extract has more aromatic content than the others and it has the ability to increase coke strength and decrease the fluidity of coal, which proves that CCO can be an effective solvent for coal extraction.

Larger CAr/CAl ratio leads to higher aromaticity. The CAr/CAl ratio exceeds 1.00 (viz. fa value > 0.50) when the preheating treatment temperature is higher than 300°C; moreover, the EA analysis also shows a sudden increase of C/H ratio at the same temperature. The initial pyrolysis temperature is clearly visible in Fig. 1(b) when the preheating treatment temperature is below 300°C. As the preheating treatment temperature increases, the pyrolysis gradually diminishes due to the high-temperature preheating treatment.25 Thermoplasticity analysis of the SCB with a 5 wt% addition of QN-extracted extract after the preheating treatment is shown in Fig. 2(b), which also shows a sudden decrease of the fluidity when the preheating treatment temperature is 300°C.

3.6. X-ray diffraction analysis. Coal is mainly composed of a wide variety of organic 10 ACS Paragon Plus Environment

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substances and its core structure is PAHs with side chains; furthermore, it also has a significant amount of amorphous carbon which is considered to be responsible for the background intensity of X-ray diffraction patterns of coal. As the temperature increases during the coking process, the bond of the aliphatic/aromatic side chain connected to aromatic carbon will break and then condense into the coal to be a microcrystalline structure which is similar to the graphite structure; therefore, graphite is usually used as a reference material.26

With regard to the X-ray diffraction pattern of graphite, which is a commercial graphite being used here (99+%, Acros Organics, Geel, Belgium), the diffractogram is shown in Fig. 5(a). The (002) and (100) peaks are observed at 2θ  26° and 43°, respectively,27 and the 2θ positions can be confirmed by comparing with the crystal structure database.28 Graphite has a layer structure and shows a high degree of crystallization in comparison with coal. The diffraction pattern of anthracite, which is shown in Fig. 5(b), has a broad hump at diffraction angles around 20° (so-called γ-band, derived from aliphatic chains) to 26° (so-called π-band, derived from aromatic ring stacking).29 The coal rank is correlated to the peak intensity at 2θ positions of 20° and 26° which is the rank ratio I26/I20; besides, this ratio is also proportional to the fa value.30

According to Fig. 6(a), Coal-II has an obviously stronger intensity of π-band in comparison to Coal-I, which implies that Coal-II contains more aromatic carbon than Coal-I. The rank ratio of Coal-I and Coal-II are 0.96 and 1.35, respectively; thus, the fluidity of Coal-I (433 ddpm) is evidently higher than that of Coal-II (15 ddpm). As mentioned above, the abundance of aromatic carbon have a significant influence upon the fluidity of coal, i.e., the coal exhibiting lower fluidity consists mainly of the larger size of the aromatic cluster with fewer substituents on the aromatic ring and has a higher density of cross-linking structure. Also, in contrast to low-fluidity coal, high11 ACS Paragon Plus Environment

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fluidity coal has relatively lower aromaticity.31,32 Fig. 6(b) shows the X-ray diffraction patterns of Coal-I before and after the high-temperature preheating treatment; both of the (002) and (100) peaks can be seen clearly in the spectra. The (002) and (100) peaks represent the mean stacking of the aromatic layers and the mean size of the aromatic layers, respectively.9,33 Coal-I after treated at 850°C for 30 min exhibits the intensified (002) and (100) peaks along with the decrease of the γ-band, which means that the degree of graphitization increases under carbonization conditions.34 The rank ratio of Coal-I and Coal-I-850 are 0.92 and 1.61, respectively, which also reveals that the aromaticity increases after the preheating treatment.

The similar tendency of the γ-band and π-band intensity variations and the trend of the rank ratio corresponding to the preheating treatment temperature were observed in the NMP-extracted extract, as shown in Fig. 7. In addition, the peaks of the γ-band and π-band become sharper with the increase of preheating treatment temperature, which indicates that the degree of graphitization increases with the formation of the polycyclic aromatic structure due to the intramolecular condensation. Thermal cracking of the covalent bond in coal structure may also take place during the heat treatment such as the cleavage of the methylene group, the alkyl side chain of aromatic carbon, and the oxygen-containing functional groups.10,26,34 These thermal cracking reactions reduce the abundance of aliphatic carbon, thereby increasing the rank ratio, the aromaticity as well as the degree of graphitization.

4. CONCLUSIONS

Solvent-extracted extract of Coal-III after the preheating treatment was investigated by EA and 12 ACS Paragon Plus Environment

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TGA, which shows that the preheating treatment leads to the increase of carbon content due to the decrease of hydrogen content. The coal extract after the preheating treatment possesses the highermolecular-weight residual material and a higher degree of graphitization, which exhibits less ability to increase the fluidity of coal and less improvement in the coke strength when adding to the SCB. 13C SSNMR and XRD are used here to elucidate the relationship between aromaticity and fluidity. The fluidity decreases with the increase of integrated intensities of SSNMR for the chemical shift interval of aromatic carbon, which indicates that the higher aromaticity results in lower fluidity. A positive relationship between the ratio of aromatic carbon to aliphatic carbon (CAr/CAl) and the aromaticity (fa value) is found. Besides, the CAr/CAl ratio and the fa value can be calculated from the diffraction angle 2θ positions of 20° and 26° on the basis of XRD spectra.30 Summing up the results of the analysis, the fluidity of coal is found to be governed by fa value which is affected by the degree of graphitization; therefore, XRD method is expected to be a simple, effective and non-destructive way to estimate the fluidity of coal in coal chemistry.

ASSOCIATED CONTENT

Supporting Information

Solid-state 13C NMR spectra for the graphite, anthracite, Coal-III, solvent-extracted coal extracts, and thermal extraction residue of coal, along with the integrated intensities for each subdivided interval.


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AUTHOR INFORMATION

Corresponding Author

* E-mail address: [email protected] (T.-J. Whang)

Notes

The authors declare no competing financial interest.

ACKNOWLEDGEMENTS

Financial support from the China Steel Corporation (Kaohsiung, Taiwan) under contract number RE99011 is acknowledged. One of us (C.-C.C.) would like to acknowledge the careful reading and

helpful suggestions on details of the manuscript provided by Rui-En Hsu.


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(24) Solum, M. S.; Pugmire, R. J.; Grant, D. M. 13C solid-state NMR of Argonne premium coals. Energy Fuels 1989, 3, 187–193.

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Table 1. Fundamental analysis of the raw coals. EA (wt%, daf)a Raw coal

C

H

N

S

Ob

C/H ratio

Max. Ash d R.M.c P.T. V.M.e content o fluidity (wt%) ( C ) (%) (%) (ddpm)

Coal-I

78.20 5.35 2.13 0.65 13.67

1.22

64.93

477

33.2

6.22

433

Coal-II

81.42 4.51 1.84 0.74 11.49

1.50

83.78

512

17.4

10.09

15

Coal-III

73.60 5.26 1.67 0.64 18.83

1.17

66.21

464

34.9

9.54

120

a

Dry and ash-free. By difference. c Remaining material: ash left after TGA. d Pyrolysis temperature: sample begin to pyrolyze in TGA. e Volatile material. b


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Energy & Fuels

Table 2. Elemental analysis of Coal-III extracts extracted with various solvents and further treated at different pretreatment temperatures. All values are in weight ratio. 25°C

150°C

300°C

450°C

600°C

Residuea

C/H

14.39

13.68

15.44

19.56

27.10

13.74

C/O

6.85

4.55

4.53

4.93

5.12

3.21

C/H

14.32

14.39

15.54

20.05

28.48

15.08

C/O

5.80

5.67

4.40

5.13

6.37

4.39

C/H

13.26

14.01

15.85

19.87

28.31

18.25

C/O

7.99

6.09

4.37

6.16

6.47

2.44

C/H

16.95

17.01

18.11

20.75

30.69

15.06

C/O

11.83

12.93

7.86

5.03

9.93

4.02

NMP

QN

NMP/QN

CCO a

Residue: thermal extraction residue of coal.


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Table 3. Aromatic to aliphatic carbon ratio (CAr/CAl), carbon aromaticity (fa), and integrated intensity of solid-state 13C-NMR of various intervals. All values are in percentage unless otherwise indicated.a Integrated intensity of various chemical shift intervals Sample

100120

120145

145160

CAr 100160

CAr/CAl

fa

0-25

25-35

35-65

CAl 0-65

Graphite

10.54

8.89

6.07

25.50

14.91 57.25

2.33

74.50

2.92

0.74

Anthracite

16.88

3.04

11.68 31.60

29.61 32.37

6.42

68.40

2.16

0.68

Coal-III

21.17

18.28

17.10 56.55

12.73 25.54

5.17

43.44

0.77

0.43

NMP

23.30

20.41

15.54 59.25

12.00 25.58

3.17

40.75

0.69

0.41

NMP(R)b

22.34

18.62

16.24 57.20

12.78 25.13

4.89

42.80

0.75

0.43

NMP-150

25.79

20.14

14.57 60.50

11.46 24.36

3.69

39.51

0.65

0.40

NMP-300

20.66

17.74

12.22 50.62

12.39 32.52

4.47

49.38

0.98

0.49

NMP-450

18.10

9.13

9.10

36.33

15.45 43.45

4.78

63.68

1.75

0.64

NMP-600

8.55

7.53

7.08

23.16

17.08 55.16

4.59

76.83

3.32

0.77

NMP/QN

28.18

19.59

12.32 60.09

13.39 23.11

3.41

39.91

0.66

0.40

NMP/QN (R)b

22.69

14.71

8.44

17.74 32.40

4.01

54.15

1.18

0.54

QN

27.17

17.84

11.14 56.15

9.29

30.71

3.85

43.85

0.78

0.44

QN(R)b

19.17

19.97

15.96 55.10

11.63 28.80

4.48

44.91

0.82

0.45

CCO

20.39

11.18

11.57 43.14

18.53 32.55

5.77

56.85

1.32

0.57

CCO(R)b

20.73

19.46

19.71 59.90

9.31

3.52

40.09

0.67

0.40

a b

45.84

27.26

Percentage of SSNMR signal of different chemical shift intervals; CAr/CAl and fa are in ratio form. (R): Thermal extraction residue of coal.


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Energy & Fuels

Figure 1. Thermogravimetric analysis of coal extract: (a) extracted with various solvents; (b) extracted with NMP after the preheating treatment at different temperatures.


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Figure 2. Thermoplastic properties of the standard coal blend with a 5 wt% addition of Coal-III extract: (a) extracted with different solvents; (b) QN-extracted extract after the preheating treatment at different temperatures.


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Energy & Fuels

Figure 3. Results of the Roga test of standard coal blend with a 5 wt% addition of Coal-III extract extracted with QN (black solid squares) and CCO (red solid circles) after preheating treatment at different temperatures.


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Figure 4. The CAr/CAl ratio (red solid circles) and the fa value (blue solid squares) of the coal extract extracted with NMP and then treated at different pretreatment temperatures.


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Figure 5. X-ray diffraction pattern of (a) graphite and its (002), (100), (101), and (004) planes, and (b) anthracite and its γ- and π-bands.


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Figure 6. X-ray diffraction pattern of (a) Coal-I and Coal-II (0.10°/step) and (b) Coal-I before and after the heat treatment at 850°C (0.02°/step).


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Energy & Fuels

Figure 7. X-ray diffraction pattern of the NMP-extracted extract of Coal-III after the preheating treatment at different temperatures. Note that the numeric value after the solvent abbreviation (e.g. NMP-150) represents the preheating treatment temperature of the coal extract.


Energy & Fuels

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Thermogravimetric analysis of coal extract: (a) extracted with various solvents; (b) extracted with NMP after the preheating treatment at different temperatures. 297x227mm (150 x 150 DPI)

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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

Energy & Fuels

Thermoplastic properties of the standard coal blend with a 5 wt% addition of Coal-III extract: (a) extracted with different solvents; (b) QN-extracted extract after the preheating treatment at different temperatures. 297x227mm (150 x 150 DPI)


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

Results of the Roga test of standard coal blend with a 5 wt% addition of Coal-III extract extracted with QN (black solid squares) and CCO (red solid circles) after preheating treatment at different temperatures. 297x227mm (150 x 150 DPI)


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Page 33 of 36

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

The CAr/CAl ratio (red solid circles) and the fa value (blue solid squares) of the coal extract extracted with NMP and then treated at different pretreatment temperatures. 297x227mm (150 x 150 DPI)


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

X-ray diffraction pattern of (a) graphite and its (002), (100), (101), and (004) planes, and (b) anthracite and its γ- and π-bands. 297x209mm (150 x 150 DPI)


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Energy & Fuels

X-ray diffraction pattern of (a) Coal-I and Coal-II (0.10°/step) and (b) Coal-I before and after the heat treatment at 850 °C (0.02°/step). 297x227mm (150 x 150 DPI)


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

X-ray diffraction pattern of the NMP-extracted extract of Coal-III after the preheating treatment at different temperatures. Note that the numeric value after the solvent abbreviation (e.g. NMP-150) represents the preheating treatment temperature of the coal extract. 297x209mm (150 x 150 DPI)


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Thermoplastic Properties of Coal and Coal Extract - Energy & Fuels

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