3.1 Coal Properties
Proximate, Ultimate, Gross Calorific Value (GCV) and Petrographic analyses data of the raw coals are shown in Table 2. The VMdmf contents show that (MH, GT and SL) belong to medium volatile coals (25.8 – 30.3 %), while ST having 21.0 wt % VM yield belongs to low volatile coal. Fixed carbon (FCdmf) ranged between 69.7 – 79.0 % and GCVdmf of the samples vary between 8450 – 8640 kcal/kg and are of high maturity.
Petrographic analyses of coals reveal vitrinite reflectance (VRr) 0.85 – 1.24 % (Table 2). Mineral free vitrinite content varies between 70.8 and 37.9 %, liptinite 0.4 and 4.6 % and inertinite between 37.9 and 70.8 %. The volatile matter yield is the combined effect of maceral contents of the coals (Borrego et al. 2000; Guerrero and Borrego 2013). It is considered to be the highest for liptinite maceral followed by vitrinite and inertinite. It can be seen from the analyses that liptinite content of the samples are not very significant. Hence a plot between vitrinite content and volatile matter was drawn (Fig. 3) which shows a straight line curve with R2 value of 0.87. Also, the VM is considered as the function of hydrogen and hydrogen content decreases with decrease in VM (Table 2).
SN
|
VMdmf
|
FCdmf
|
GCVdmf
|
Cdmf
|
Hdmf
|
Sdmf
|
Ndmf
|
Odmf
|
Vmmf
|
Lmmf
|
Immf
|
VRr%
|
wt %
|
wt %
|
kcal/kg
|
wt %
|
wt %
|
wt %
|
wt %
|
wt %
|
Volume %
|
Dry mineral free basis
|
Mineral matter free basis
|
MH
|
30.3
|
69.7
|
8550
|
86.46
|
5.87
|
0.47
|
1.91
|
5.30
|
70.8
|
4.6
|
24.6
|
0.85
|
GT
|
28.1
|
71.9
|
8630
|
87.37
|
5.44
|
0.65
|
1.71
|
4.82
|
63.7
|
0.4
|
35.9
|
1.05
|
SL
|
25.8
|
74.2
|
8640
|
89.02
|
5.23
|
0.80
|
1.98
|
2.97
|
43.9
|
0.9
|
55.2
|
1.17
|
ST
|
21.0
|
79.0
|
8450
|
90.88
|
5.19
|
0.64
|
1.82
|
1.82
|
37.9
|
2.9
|
59.2
|
1.24
|
Table 2: Proximate, Ultimate, Gross Calorific value and Petrographic analyses of coals
Explanations: SN= sample name, VM= volatile matter yield, FC= fixed carbon, GCV= gross calorific value, C=carbon, H=hydrogen, S=sulphur, N=nitrogen, O=oxygen, dmf= dry mineral free V=vitrinite, L=liptinite, I=inertinite, MM= mineral matter, VRr = mean random reflectance of vitrinite, mmf= mineral matter free basis.
Fig. 3: Relation of Vitrinite content with respect to Volatile Matter.
3.2 Changes in weight on nitration
The change in weight due to treatment is shown in Table 3. It is observed that in glacial acetic acid medium, the weights of the samples have increased. Since, the medium is non-aqueous; less oxidation has taken place in the coal moieties resulting into gain in weight of all the studied samples. MH coal shows reduction in weight (shown with negative sign in the Table 3) in the case of nitration in aqueous medium. Rest of the samples treated with aqueous nitric acid has gained weight. MH being low in rank (VRr = 0.85 %) in comparison to the other three samples, oxidation is predominant phenomenon with simultaneous nitration in aqueous medium which has removed the aliphatic side chains resulting into decrease in weight of the said samples. Nitration is the predominant phenomena with simultaneous oxidation in stronger aqueous medium for higher rank coals.
Sl. No.
|
SN
|
G. Ac. Acid+HNO3
|
Aq.HNO3
|
|
|
Change in wt %
|
Change in wt %
|
1
|
MHD
|
19.08
|
-10.39
|
2
|
GTD
|
19.78
|
13.59
|
3
|
SLD
|
15.29
|
15.00
|
4
|
STD
|
16.37
|
15.44
|
Table 3: Change in weight due to nitration
Fig. 4: Relation of d002 with respect to Volatile Matter.
3.3 X-ray Diffraction studies
The results of X-ray scattering analysis are shown in Table 4. The d002 values of demineralized coals [d002 Å (D)] are plotted against VMdmf wt% (Table 2) and shown in Fig. 4. It is observed that d002 decreases with decrease in VMdmf wt% and maintains a linear relationship with coefficient of determination, R2=0.82. It is known that d002 decreases with increase in maturity, vis-à-vis decrease in volatile matter yield of the coal (Lu et al. 2001).
It is found that the corresponding inter layer spacing of π- band (d002) are the least for raw coals followed by d002 values of treated coals in aqueous medium and then to glacial acetic acid medium (Table 4). The d002 values of demineralized coals as well as treated coals are plotted against dry mineral free carbon of coal samples (Cdmf) which is shown in Fig. 5.a – 5c and it is observed that d002 value decreases with the increase of Cdmf. A similar relationship was found between d002and elemental carbon (Maity and Mukherjee 2006; Sonibare et al. 2010, Manoj and Kunjonama 2012) for demineralized coals where a linear relationship between d002 and elemental Cdmf was established. The nature of the graphs is similar for the demineralized as well as treated coals. An inverse relationship is found between Cdmf and d002 (D), with increase in Cdmf content d002 decreases with R2= 0.88 (Fig. 5a). Similar trend is also observed for the chemically modified coals having R2= 0.93 and R2= 0.94 for d002 (G) and d002 (A) respectively (Fig. 5b & 5c).
S N
|
d002 (Å)
|
Lc(Å)
|
fa
|
Nc
|
I26/I20
|
Dγ(Å)
|
MHD
|
3.484
|
23
|
0.44
|
6.60
|
1.82
|
4.30
|
MHG
|
3.487
|
21
|
0.47
|
6.02
|
1.56
|
4.14
|
MHA
|
3.486
|
21
|
0.68
|
6.02
|
2.90
|
4.20
|
GTD
|
3.471
|
25
|
0.50
|
7.20
|
1.97
|
4.27
|
GTG
|
3.480
|
21
|
0.51
|
6.03
|
1.75
|
4.26
|
GTA
|
3.473
|
22
|
0.71
|
6.33
|
2.95
|
4.31
|
SLD
|
3.454
|
25
|
0.52
|
7.24
|
2.20
|
4.19
|
SLG
|
3.466
|
23
|
0.53
|
6.64
|
1.85
|
4.18
|
SLA
|
3.460
|
23
|
0.72
|
6.65
|
3.09
|
4.12
|
STD
|
3.451
|
25
|
0.53
|
7.24
|
2.54
|
4.03
|
STG
|
3.462
|
24
|
0.54
|
6.93
|
2.21
|
4.28
|
STA
|
3.452
|
24
|
0.73
|
6.95
|
3.38
|
4.07
|
Table 4: XRD analysis of demineralized and nitric acid treated coals
It is found that the corresponding d002 values of coals treated with nitric acid in glacial acetic acid and aqueous media are increased. Aqueous medium being stronger in the present studied mediums might have dissolved the more aliphatic content of coal resulting in relative increase of aromatic moieties which lead to decrease in inter layer spacing (d002) in comparison to nitration in glacial acetic acid medium.
The results of mean crystallite size (Lc) of demineralized coals and their SMCs formed due to nitration in glacial acetic acid medium and in aqueous medium are shown in Table 4. The Lc values of demineralized coals increase with increase in carbon content and vitrinite reflectance indicating crystallite sizes increase with increase in rank of the coals (Table 2 & 4). Due to nitration, the disordering of molecular structure has taken place leading to decrease in mean crystallite size (Lc) of SMCs in comparison to the demineralized coals. Similar studies were carried out by several other workers (Sonibare et al. 2010; Manoj and Kunjonama 2012) and corroborates with the present study.
The variation of aromaticity (fa) of demineralized as well as nitric acid treated coal in glacial acetic acid medium and aqueous medium are shown in Table 4. It is found that corresponding fa values are least for demineralized coals followed by treated coals in glacial acetic acid medium and then to aqueous medium. The increase in aromaticity in aqueous nitric acid treated coals is much more than that of nitration in glacial acetic acid medium. This suggests that aqueous medium is stronger than that of glacial acetic acid medium and is capable of removing more aliphatic contents resulting in more increase in aromaticity. The change in weight in both the media also indicates towards a similar conclusion (Table 3). The aliphatic contents are easily removed by aqueous nitric acid resulting into decrease in weight for MH coal and for relatively higher rank coals also the increase in weight is less in comparison to nitric acid treated coals in glacial acetic acid medium.
The vitrinite reflectance (VRr) is also plotted against fa and shown in Fig. 6a – 6c. It shows an almost straight line relationship with coefficient of determination of R2=0.96 for demineralized coals, R2=0.9958 for treated coals in glacial acetic acid and R2 = 0.998 for coals with nitration in aqueous medium. It is to mention here that vitrinite reflectance is a very good indicator of rank and suggests that the aromaticity is more dependent on rank of the coals. The significant finding of this study is that nitration in the aromatic structure of coals is the predominant phenomenon with simultaneous oxy-destruction of aliphatic side chains resulting increase in the aromaticity. It also shows that aqueous medium being stronger between two media used for formation of SMCs of present study is capable of removing more aliphatic components resulting into more aromaticity of the samples in the said medium.
The average number of aromatic layers (Nc) for demineralized and the treated coals are shown in Table 4. It can be observed that Nc have increased with increase in Cdmf content (Table 2). Similar kind of relationship between Nc and Cdmf has also been observed for demineralized pyrolyzed coals (Takagi et al. 2004) as observed in the present work. Also, the Nc values are maximum for demineralized samples followed by the corresponding nitric acid treated coals in aqueous medium and then to glacial acetic acid medium. This suggests that in treated coals, the structure of the coals is disordered due to nitration which reduced the average aromatic layers of SMCs. The degree of disorder is more in the case of glacial acetic acid treated coals than in aqueous medium.
The results of intensity ratio of π- and γ- band (I26/I20) is also known as X-ray rank parameter and for demineralized and treated coals in both the media are shown in Table 4. The variation of I26/I20 values of raw as well as treated coals are plotted against Cdmf content and shown in Fig. 7.a – 7c. The nature of curves is similar for raw as well as treated coals in both the nitration media. A very good linear fit of the curves are observed having R2=0.9963 for demineralized coal (Fig 7a). The nitric acid treated coals show linear increase of R2 = 0.96 in glacial acetic acid medium and aqueous medium respectively (Fig. 7b and Fig. 7c). Thus, the chemical (Cdmf) and X-ray (I26/I20) rank parameters agree with each other to express the maturity of coal. Inter-layer spacing of γ-band (Dγ) occurs around 20° and is believed to be derived from aliphatic side chains of coal molecules. The Dγ values obtained for demineralized and SMCs formed do not show any trend in the present study (Table 4).
3.4 Fourier Transform Infrared Spectroscopy (FTIR)
The broad strong stretching band of –OH (hydroxyl) group is shown in the range of 3600 –3200 cm-1 produced mainly due to moisture in coal. In some of the samples stretch band of alkene (=CH2) of small to medium intensity of (3100 – 3010cm-1) are observed. The 2950 – 2800 cm-1 appeared as sharp peak of medium intensity and are assigned to aliphatic and alicyclic –CH3, –CH2 and –CH groups; though the major contributor is the –CH2 groups. The peaks ~1700 cm-1 has appeared due to strong stretching band of carbonyl/ketone (C=O) group. The bending vibration of alkane (-CH3) appears in the range of 1470 – 1350 cm-1. The peaks ~1600 cm-1 are observed due to medium to stretching bands of C=C aromatic compounds. Ester and/or ether groups are formed at 1320 – 1210 cm-1. The region between 900 – 700 cm-1 is assigned to various bands related to aromatic, out-of-plane C-H bending, –OH group with different degree of substitution.
In the samples of nitric acid treated coals, both in glacial acetic acid medium and aqueous medium, a distinct stretch asymmetric strong band of nitro (-NO2) groups of aromatic compound appears in the range of 1550 – 1490 cm-1. A –CH3 bending band and –CH2 group in bridges of variable intensity has been observed in the range of 1430 – 1290 cm-1. It has also been observed that strong stretch symmetrical nitro (NO2) group appears in the range of 1355 – 1315 cm-1 in nitric acid treated coals in both the media. Covalent nitro-groups (Ar–O–NO2) are formed at 1255-1300 cm-1. A strong stretch band of ether (C–O) appeared in 1300 – 1000 cm-1. A deformation bending arene bond of nitro-groups is absent in the range of 860 – 840 cm-1.
The FTIR curves of demineralized coals, nitration in glacial acetic medium and nitration in aqueous medium are suffixed by D, G and A respectively and shown in Fig. 8 to Fig. 11. The areas of functional groups for all the demineralized as well as nitric acid treated coals in both non-aqueous and aqueous medium have been calculated by Gaussian probability density function using Origin 6.1 software and shown in Table 5 – Table 8. In order to quantify the replacement of aliphatic side chains by nitro groups an attempt has been made to measure the area under peaks of aliphatic and alicyclic (-CH) functional group of vibration (2950 – 2800 cm-1) and bending vibration of alkane (-CH; 1470 – 1350 cm-1) are added for demineralized (raw) coals and corresponding nitric acid treated coals in both the media. The decrease in total areas of alkane group of raw and treated coals suggests the replacement of aliphatic side chains by nitro group. Total area of -CH3 group is decreased from 13.72 cm2 at 2917 cm-1, 2853 cm-1 and at 1441 cm-1 for demineralized coal to 10.76 cm2 at 2922 cm-1, 2856 cm-1 and at 1449 cm-1 for MHG coal (Table 5a & 5b). Total area decreased to 13.62 cm2 of -CH3 group in MHA at 2924 cm-1, 2853 cm-1 and at 1450 cm-1 coal (Table 5a & 5c).
MHD
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3420
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
1.54
|
3043
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.86
|
2917
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
4.00
|
2853
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
3.01
|
1897
|
=C-H
|
Alkene
|
Stretch, asymmetric
|
Strong
|
0.48
|
1595
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
16.66
|
1441
|
-C-H
|
Alkane
|
Bending
|
Variable
|
6.72
|
1368
|
N=O
|
Nitro
|
Stretch, symmetric
|
Strong
|
1.19
|
1215
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
41.00
|
863
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.42
|
811
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
2.46
|
749
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
2.91
|
Table 5a
MHG
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3423
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
16.46
|
3069
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.44
|
2922
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
6.03
|
2856
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
2.72
|
1926
|
=C-H
|
Alkene
|
Stretch, asymmetric
|
Strong
|
0.82
|
1713
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
9.27
|
1608
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
19.78
|
1531
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
5.73
|
1449
|
-C-H
|
Alkane
|
Bending
|
Variable
|
2.01
|
1372
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
5.78
|
1333
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
65.14
|
1032
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
2.56
|
892
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.06
|
822
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.54
|
753
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
1.11
|
Table 5b
MHA
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3435
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
34.42
|
3084
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
6.88
|
2924
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
8.82
|
2858
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
3.77
|
2517
|
O-H
|
Carb. Acid
|
Stretch/Broad
|
Strong
|
3.63
|
1943
|
=C-H
|
Alkene
|
Stretch, asymmetric
|
Strong
|
1.89
|
1718
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
45.95
|
1610
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
43.94
|
1537
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
14.74
|
1450
|
-C-H
|
Alkane
|
Bending
|
Variable
|
1.02
|
1341
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
1.17
|
1260
|
C-O/Ar-O-NO2
|
Ether/Ester/Covalent Nitrate
|
Stretch
|
Med-Weak
|
122.15
|
909
|
=C-H
|
Alkene
|
Bending
|
Strong
|
0.72
|
763
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
6.63
|
Table 5c
Table 5: FTIR analysis of Mohuda (MH) coal
Likewise, total area of 33.91 cm2 of -CH3 group in raw coal at 2917 cm-1, 2856 cm-1 and at 1439 cm-1 is decreased to 21.47 cm2 at 2923 cm-1, 2856 cm-1 and at 1452 cm-1 in GTG coal (Table 6a & 6b) and total area of CH3 group is decreased to 13.59 cm2 at 2923 cm-1, 2859 cm-1 and at 1447 cm-1 for SMC in aqueous medium (Table 6a & 6c).
GTD
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3414
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
2.18
|
3033
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.32
|
2917
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
11.63
|
2856
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
8.17
|
1596
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
5.43
|
1439
|
-C-H
|
Alkane
|
Bending
|
Variable
|
14.11
|
1368
|
N=O/C-H
|
Nitro/Alkane
|
Stretch, symmetric
|
Strong/variable
|
0.82
|
1320
|
C-N
|
Amine
|
Stretch
|
Strong
|
0.92
|
1032
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
0.72
|
866
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.92
|
808
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.36
|
748
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
1.99
|
Table 6a
GTG
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3432
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
5.81
|
3065
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.44
|
2923
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
10.34
|
2856
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
3.61
|
1913
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
1.45
|
1707
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
5.54
|
1602
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
13.39
|
1525
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
9.24
|
1452
|
-C-H
|
Alkane
|
Bending
|
Variable
|
7.52
|
1329
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
14.35
|
1030
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
9.34
|
888
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.64
|
820
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.22
|
751
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
2.43
|
Table 6b
GTA
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3437
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
55.15
|
3077
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
1.24
|
2923
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
4.50
|
2859
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
2.27
|
2506
|
O-H
|
Carb. Acid
|
Stretch/Broad
|
Strong
|
2.29
|
1934
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
6.03
|
1715
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
39.29
|
1606
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
48.28
|
1532
|
N=O
|
Nitro Arene
|
Stretch, asymme
|
Strong
|
14.19
|
1447
|
-C-H
|
Alkane
|
Bending
|
Variable
|
6.83
|
1339
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
4.06
|
1256
|
C-O/Ar-O-NO2
|
Ether/Ester/Covalent Nitrate
|
Stretch
|
Med-Weak
|
122.29
|
905
|
=C-H
|
Alkene
|
Bending
|
Strong
|
0.94
|
826
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.77
|
759
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
7.73
|
Table 6c
Table 6: FTIR analysis of Gasalitand (GT) coal
Total areas of -CH3 group in demineralized coal at (2917 cm-1, 2854 cm-1 and at 1439 cm-1) is 13.91 cm2 decreased to 13.05 cm2 in SLG (2921 cm-1, 2855 cm-1 and at 1446 cm-1; Table 7a & 7b) and area of CH3 group is decreased to 7.54 cm2 at 2922 cm-1, 2856 cm-1 and at 1449 cm-1 in SLA coal (Table 7a & 7c).
SLD
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3440
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
0.12
|
3043
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.66
|
2917
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
0.94
|
2854
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
0.49
|
1897
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
0.45
|
1594
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
7.95
|
1439
|
-C-H
|
Alkane
|
Bending
|
Variable
|
12.48
|
1220
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
27.44
|
865
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.19
|
807
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
2.00
|
748
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
3.65
|
Table 7a
SLG
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3435
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
7.79
|
3058
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
1.22
|
2921
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
5.61
|
2855
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
2.83
|
1916
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
3.78
|
1703
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
8.71
|
1599
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
23.07
|
1524
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
10.30
|
1446
|
-C-H
|
Alkane
|
Bending
|
Variable
|
4.61
|
1326
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
88.03
|
886
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.36
|
820
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.30
|
751
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
3.06
|
Table 7b
SLA
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3422
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
20.66
|
2922
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
4.53
|
2856
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
1.94
|
1930
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
2.21
|
1711
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
9.68
|
1605
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
22.15
|
1528
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
7.05
|
1449
|
-C-H
|
Alkane
|
Bending
|
Variable
|
1.08
|
1374
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
0.64
|
1334
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
2.56
|
1274
|
C-O/Ar-O-NO2
|
Ether/Ester/Covalent Nitrate
|
Stretch
|
Med-Weak
|
65.66
|
895
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.14
|
825
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.59
|
754
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
2.29
|
Table 7c
Table 7: FTIR analysis of Salanpur (SL) coal
Total areas of CH3 group in demineralized coal at (2918 cm-1, 2854 cm-1 and at 1440 cm-1) is 20.56 cm2 decreased to 20.13 cm2 in STG (2922 cm-1, 2856 cm-1 and at 1452 cm-1; Table 8a & 8b) and total area of -CH3 group decreased to 19.99 cm2 in STA at 2922 cm-1, 2857 cm-1 and at 1447 cm-1 (Table 8a & 8c).
STD
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3414
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
5.76
|
3042
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.95
|
2918
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
4.33
|
2854
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
1.82
|
1901
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
0.47
|
1599
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
31.25
|
1440
|
-C-H
|
Alkane
|
Bending
|
Variable
|
14.41
|
1253
|
C-O
|
Ether/Ester
|
Stretch
|
Strong
|
35.60
|
874
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.62
|
815
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
2.48
|
753
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
3.38
|
Table 8a
STG
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3427
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
17.30
|
3064
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
0.48
|
2922
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
9.57
|
2856
|
C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
3.98
|
1922
|
C=C
|
Arom./Arene
|
Stretch
|
Strong
|
0.01
|
1708
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
10.02
|
1603
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
28.04
|
1527
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
8.76
|
1452
|
-C-H
|
Alkane
|
Bending
|
Variable
|
6.58
|
1374
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
32.10
|
1333
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
54.10
|
894
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
0.44
|
826
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
1.32
|
757
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
1.96
|
Table 8b
STA
|
Wave Number (cm-1)
|
Functional Group
|
Type of Vibration
|
Intensity
|
Area (cm2)
|
3440
|
O-H
|
Phenolic/Hydroxyl
|
Stretch, H-bonded
|
Strong, broad
|
68.34
|
3077
|
=C-H
|
Alkene
|
Stretch
|
Strong
|
2.22
|
2922
|
C-H
|
Alkane
|
Stretch, symmetric
|
Strong
|
5.85
|
2857
|
=C-H
|
Alkane
|
Stretch, asymmetric
|
Strong
|
2.70
|
2516
|
O-H
|
Carb. Acid
|
Stretch/Broad
|
Strong
|
2.27
|
1941
|
=C-H
|
Alkene
|
Stretch, asymmetric
|
Strong
|
2.19
|
1717
|
C=O
|
Carbonyl/Ketone
|
Stretch
|
Strong
|
46.74
|
1607
|
C=C
|
Arom./Arene
|
Scissoring
|
Med
|
48.12
|
1533
|
N=O
|
Nitro Arene
|
Stretch, asymmetric
|
Strong
|
11.75
|
1447
|
-C-H
|
Alkane
|
Bending
|
Variable
|
11.44
|
1340
|
N=O
|
Nitro Arene
|
Stretch, symmetric
|
Strong
|
5.24
|
1264
|
C-O/Ar-O-NO2
|
Ether/Ester/Covalent Nitrate
|
Stretch
|
Med-Weak
|
113.27
|
908
|
=C-H
|
Alkene
|
Bending
|
Strong
|
2.12
|
831
|
=C-H/ C=C/N-H
|
Alkene/Arene/Amine
|
Bending
|
Strong
|
2.34
|
763
|
O-H/ C=C/N-H
|
Alcohol/Arene/Amine
|
Bending, out-of-plane
|
Weak
|
8.49
|
Table 8c
Table 8: FTIR analysis of Shatabdi (ST) coal
This is a very significant finding that the decrease in total areas of alkane groups of demineralized and treated coals suggests the replacement of aliphatic side chains by nitro group.