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Investigation of mineral composition of oil shale.

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ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
Published online 25 June 2009 in Wiley InterScience
(www.interscience.wiley.com) DOI:10.1002/apj.319
Special Theme Research Article
Investigation of mineral composition of oil shale
Dong-Mei Wang,1 Ying-Mei Xu,2 De-Min He,1 Jun Guan1 and Oiu-Min Zhang1,3 *
1
Institute of Coal Chemical Engineering, Dalian University of Technology, Dalian, 116012, China
School of Biological Science of Dalian Nationalities University, Dalian, 116600, China
3
State Key Laboratory of Fine Chemical, Dalian University of Technology, Dalian, 116012, China
2
Received 30 October 2008; Revised 28 February 2009; Accepted 4 March 2009
ABSTRACT: The aim of this paper is to identify the mineral composition of oil shale from different locations and relate
it to their interval of occurrence. Thermogravimetric analysis (TGA), diffuse reflectance infrared Fourier transforms
spectroscopy (DRIFTS) and X-ray diffraction (XRD) methods were used for this invetigation. Hydrogen peroxide
was used as the oxidant to eliminate the influence of organic matter in TGA. DRIFTS results indicated that most of
the kerogen is in aliphatic hydrocarbon form and the peak of hydrocarbon nearly disappeared after oxidation. XRD
results indicated that quartz, muscovite, kaolinite and calcite are the dominant minerals. Longkou and Changchun oil
shale samples contain high percentage of calcite (12.9 and 11.7% CO2 respectively) while Fushun and Huadian oil
shale samples contain less than 6% CO2 . Especially, in Fushun oil shale sample, the content is below 3%. Kaolinite
is found in Fushun oil shale sample, while muscovite is only found in Huadian oil shale sample. Integration of the
XRD, DRIFTS and TGA results of the oil shale samples from different locations has provided a better way of mineral
composition identification.  2009 Curtin University of Technology and John Wiley & Sons, Ltd.
KEYWORDS: mineral composition; TGA; DRIFTS; XRD; oil shale
INTRODUCTION
Oil shale is a sedimentary rock containing a complex
organic substance called kerogen, which is a valuable
source of energy as it can be converted to oil, and a
series of mineral composition[1] . Therefore, it is important to estimate the kerogen content and the possible oil
yield in an oil shale. The widely used industrial method
of evaluating the oil yield from oil shale samples is the
modified Fisher assay (MFA)[2,3] . This method is time
consuming, destructive and expensive. Large number
of oil shale samples is required to be tested in order
to determine the validity and the feasibility of oil shale
mining and processing. Quantitative analysis of mineral
composition is important for the comprehensive utilization of oil shale. Previous researchers acknowledged the
fact that the minerals in the oil shale influence the conversion of kerogens and the release of oil during oil
shale processing (retorting). Minerals such as smectite,
kaolinite, calcite, pyrite and siderite have been noted
to have effect on the processing of oil shale. Patterson et al .[4] did substantial research on Australian oil
shale from different deposits. Their main focus was on
*Correspondence to: Oiu-Min Zhang, Institute of Coal Chemical
Engineering and State Key Laboratory of Fine Chemical, Dalian
University of Technology, Dalian, 116012, China.
E-mail: qmzhang@chem.dlut.edu.cn
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
the mineralogy of Australian oil shale and its effect on
oil shale retorting. They identified that smectite, kaolinite, calcite, pyrite and siderite have the largest effects
on the processing of Australian oil shale. Karabakan
and Yurum[5] studied the effects of mineral matrix in
the reactions of oil shales using pyrolysis and oxidation
reactions of Turkish Goynuk and US Green River oil
shales. They reported the inhibition effects of silicate
minerals and catalytic effects of the carbonate minerals
on the pyrolysis reactions of the samples studied. Therefore, when characterizing oil shales, it is imperative to
know the accurate mineral contents of the samples.
Thermogravimetric analysis (TGA)/Differential thermal analysis (DTA) instrument has been used previously to determine the characteristics of decomposition,
effect of temperature on thermal degradation and kinetic
parameters of oil shale[6 – 9] . While TGA does not provide direct measure of oil yields, TGA results were
often presented according to the weight loss at different temperature regions. In general, a moderate weight
loss in the lower temperature region (up to 200 ◦ C)
can be attributed mainly to the loss of moisture and
loss of some interlayer water from clay minerals to the
decomposition of certain minerals such as nahcolite and
dawsonite. The weight loss in the middle temperature
range (200–600 ◦ C) is attributed to the decomposition
of kerogen into pyrolytic bitumen and later on to the
decomposition of bitumen into gas and liquid products.
692
D.-M. WANG ET AL.
The clay minerals such as smectite and kaolinite lose
their structural water at this temperature. Next major
phase of weight loss occurs in the temperatures between
600 and 850 ◦ C. The weight loss at this temperature region is mainly attributed to the decomposition
of carbonate minerals including calcite, dolomite and
ankerite[6,7] . In this paper, in addition to comparing the
data, attempts are made to identify the most appropriate
TGA temperature regions to be used in the prediction
of the mineral contents of oil shale.
Diffuse reflectance infrared Fourier transforms spectroscopy (DRIFTS) has an advantage of rapidly acquiring quantitative results of both shale organic and
mineral matters. In the mid-IR region, kerogen content is associated mainly with the aliphatic peak intensity at 2935 cm−1 wavelength. Also reported[2] is the
characteristic band wavenumber for ankerite occurring
at 876, 727 and 713 cm−1 , dolomite identified at 882
and 729 cm−1 , siderite identified at 873 and 741 cm−1 ,
calcite identified at 877 and 713 cm−1 and aragonite
identified at 856, 713 and 700 cm−1 . The quartz and
clay minerals were associated to the bands 800 and
1040 cm−1 , respectively. However, overlapping of different bands of kerogen with those from other minerals,
make the quantitative evaluation of minerals complex.
X-ray diffraction (XRD) plays a major role in identifying the mineral phases present in the oil shale. However, during the XRD data interpretation in oil shale
there are special considerations. Unlike in many other
rocks, oil shale has a large amount of non-diffracting
matter, mainly because of the presence of kerogen,
which is amorphous. In this study, XRD is used mainly
as a method to identify and quantify any crystallized
mineral phase present in the oil shale. XRD is the only
technique that can provide the quantitative data on crystallized mineral phases of a sample.
In this paper, three techniques, namely TGA, DRIFTS
and XRD, are used in conjunction to characterize seven
Chinese oil shale samples. The objective of this paper
is to identify the mineral composition of oil shale and
quantify the mineral content accurately using XRD,
DRIFTS and TGA. Also, this study aims at giving some
insight to the Chinese oil shale mineralogy.
Asia-Pacific Journal of Chemical Engineering
Figure 1. Sample locations in the map of China.
operation was repeated several times until the samples
were buffed. The aforementioned samples were dried
in an electronic oven at 120 ◦ C for 4 h. Then, TGA,
DRIFTS and XRD measurements were carried out to
analyze these samples. According to GB/T 218–1996,
which is used to measure the content of carbonate in
coal, the carbonate content was identified and measured
for all the samples.
TGA technique
The initial TGA temperature for all samples was 25 ◦ C
and the final temperature was 900 ◦ C. The heating rate
was 10 ◦ C/min and the tests were carried out using nitrogen purging at a rate of 20 mL/min. About 20–25 mg
from each sample was thinly spread on platinum pan
before the TGA. Hydrogen peroxide was used as the
oxidant to oxidate the organic composition. This eliminates the effect of organic composition and makes
the quantitative analysis easy. TGA results indicate the
cumulative effect of kerogen and mineral decomposition, but not the individual contribution from kerogen
of each mineral and therefore, would not provide the
complete mineral composition of the oil shale[11 – 13] .
EXPERIMENTAL
Sample material and methods
DRIFTS technique
Oil shale samples were obtained from four locations,
namely Huadian, Fushun, Longkou and Changchun in
People’s Republic of China (Fig. 1). Each sample was
crushed and mixed thoroughly and about 50 g were
separated and ground to a fine powder (<74 µm). Samples were leached with hydrogen peroxide at concentration of 10–15% at 100 ◦ C for 1 h[10] . The mixture
was filtered and washed with deionized water. This
DRIFTS tests were conducted on seven samples and
the bands that were selected for kerogen and some
mineral matter were isolated. Oil shale samples were
put in the diffuse reflectance cup (10 mm diameter and
3.3 mm depth) in which packing density was ensured
by applying a constant mass (30 g) on the top surface
of each sample. The instrument used was Perkin–Elmer
Spectrum 2000 FT-IR spectrometer fitted with a Praying
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
INVESTIGATION OF MINERAL COMPOSITION OF OIL SHALE
Mantis diffuse reflectance attachment. The spectra were
obtained at 1 cm−1 resolution and collected in the midIR region from 4000 to 400 cm−1 . Stationary cell was
used and measurements were taken at four different
orientation positions for each sample. DRIFTS can be
used to identify the hydrocarbons and indicate certain
group of minerals but evaluating total mineralogy is
however complex.
XRD technique
XRD data were collected on a Bruker AXS diffractometer D5005 with scintillation detector equipped with
a Cu tube (Cu Ka radiation), a monochromator, an
automatic variable divergent slit and 1.0 mm detector
slit. For measuring X-ray diffractograms, the following
parameters were used: tube current 40 mA, tube voltage 40 kV, step size 0.02◦ , time per step 4.0 s, scan
range from 5 to 80◦ 2θ . Care was taken to minimize the
orientation effects and displacement errors as much as
possible. Samples were not sieved in order to maintain
their homogeneity, but the particle size was maintained
under 74 µm. In order to do the best possible comparison of XRD traces, neither automatic background
subtraction nor smoothing was performed. All graphs
presented here were generated from raw data. XRD
provides a comprehensive picture on the mineralogy;
however, it does not show the amorphous contents in
detail.
RESULTS AND DISCUSSION
kerogen and some mineral matters were relatively
isolated and not significantly affected by overlapping.
The absorbance of the band is associated with aliphatic
hydrocarbon at 2935 cm−1 wavenumber. The bands for
quartz and carbonate minerals are not as noticeable
because of the scale of the Fig. 2. However, all the
samples indicate presence of quartz and a lesser extent
of calcite or dolomite. Muscovite was detected in
samples 1, 2 and 3 and kaolinite was detected in samples
4 and 5. Neither ankerite nor siderite was detected.
Carbonate minerals are detected in all the samples.
Adopting hydrogen peroxide to oxidate the organic
composition is feasible because hydrogen peroxide
hardly reacts with most of the mineral composition[10] .
The peak of hydrocarbon seems to have disappeared
after oxidating with hydrogen peroxide which suggests
that all kerogen have been removed. Other peaks
were not changed except the absorbance of the band
associated with carbonate at 1430 cm−1 wavenumber.
According to the DRIFTS result, the main mineral
compositions of the oil shale samples are quartz, clay
mineral and carbonates.
Correlations can be seen between the absorbance of
the aliphatic hydrocarbon band and shale oil values as
shown in Fig. 2. Samples 1, 2 and 3 showed higher
amount of oil shale organic than others and, sample
5 showed the least amount. This result is uniform
with chemical method and TGA result. At the same
time, it would confirm the fact that the organic matter
in the seven oil shale samples consists mainly of
aliphatic hydrocarbons. The noise in the data possibly
comes from the existence of smaller amount of nonaliphatic hydrocarbon, from other mineral matter band
interactions and also from the band overlapping.
DRIFTS technique
samples
Figure 2 shows the absorbance spectra of the seven
oil shale samples. The bands that were selected for
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
4000
sample1
sample2
sample3
sample4
sample5
sample6
sample7
3500
3000
2500
2000
1500
1000
500
Wave number/cm-1
Figure 2. DRIFTS scans for the seven oil shale samples.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
XRD technique
Kahle et al .[14] provided a review on the quantitative
analyses of clay minerals and the variabilities associated
with them. Having up to about 50% of clay, XRD
data from oil shale rocks are especially susceptible to
incorrect quantitative interpretations. All the oil shale
samples contained significant amounts of quartz. The
peaks associated with quartz are indicated in Fig. 3 and
the peak near 60◦ 2θ is the most indicative of sample
differences. However, this mineral does not directly
contribute to the weight loss in the region considered,
unless it has inhibitory or catalytic effect on the other
minerals. Exaggeration of quartz peak intensities, which
is a well-known phenomenon in XRD, was taken into
consideration during the quantification of mineralogy.
Only samples 6 and 7 had lesser amount of pyrite
and it was obviously represented in Fig. 3 in the
peak near 33◦ 2θ . Pyrite can decompose in the same
temperature range as the kerogen and is difficult to
isolate in TGA results. XRD has a clear advantage
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
DOI: 10.1002/apj
693
D.-M. WANG ET AL.
Asia-Pacific Journal of Chemical Engineering
2.2
sample1
2.0
sample2
1.8
sample3
1.6
sample4
1.4
samples
over TGA in detecting this type of minerals. And
pyrite also can react with hydrogen peroxide just like
calcite. This can be testified in Fig. 4, where the peak
near 33◦ 2θ has disappeared. All samples show high
calcite contents except samples 4 and 5 as shown in
Fig. 3. Intensity differences of the peak near 30◦ 2θ
indicate significant differences in calcite content in
these samples. The DRIFTS and XRD results showed
corresponding results regarding calcite concentration. In
the DRIFTS data, these samples showed characteristic
peaks at 1446 cm−1 wavenumber. Calcite amount will
not affect the TGA weight loss in the lower temperature
region (below 650 ◦ C), because its decomposition (to
CaO and CO2 ) needs higher temperatures. Therefore, it
is expected that calcite would not have direct impact
on the weight loss in the range of temperatures that are
considered. A few of siderite was identified in samples
4 and 5 as shown in Fig. 3. The characteristic peak is
near 32◦ 2θ . In the DRIFTS results, the corresponding
peak is at 1430 cm−1 wavenumber. The other minerals
that are clearly visible in the XRD are clay minerals.
Kaolinite and muscovite contents are shown in Fig. 3
and in Table 1. They lose the moisture below 200 ◦ C
and the crystalline water at much higher temperatures.
Although the kerogen is the most important component
of the oil shale, it cannot be detected by direct XRD
analyses. However, when combined with the data from
the other techniques, XRD provides vital information in
understanding the oil shale mineralogy and evaluating
their potential as a fuel resource.
sample5
1.2
sample6
1.0
0.8
sample7
0.6
0.4
0.2
0.0
4000
3500
3000
2500
2000
1500
1000
500
Wave number/cm-1
Figure 3. DRIFTS scans for the seven oxidated oil shale
samples.
3200
2800
Q-quartz
K-kaolinite
M-muscovite
C-calcite
S-siderite M
P-pyrite
Q
C
Q
Sample1
Q
2400
Sample2
Intensity/cps
694
2000
Sample3
1600
S
K
Sample4
1200
Sample5
800
Sample6
P
400
Sample7
0
TGA TECHNIQUE
10
The results of the TGA are presented in Table 1. The
lower temperature region, up to 200 ◦ C, produced a
moderate weight loss, as seen in Table 2. This can be
attributed mainly to the loss of moisture and loss of
some interlayer water from clay minerals[6,7] . Structural
water in the clay minerals may be released over a wide
range of temperatures up to about 550 ◦ C.
As shown in Table 2, weight loss in the 200–600 ◦ C
temperature region produced the main weight loss.
This will be contributed to the decomposition of
kerogen and the structural water release in the clay
20
30
40
50
60
70
80
2Theta/deg
Figure 4. XRD scans for the seven oil shale samples.
minerals. Decomposition of pyrite generally takes place
in 450–550 ◦ C temperature range. The main crystalline
minerals of the samples are quartz, clay mineral (kaolinite), carbonate (calcite) and pyrite. All samples contain
small percentage of pyrite, the highest is less than 2%
(Table 1) and pyrite in oxygen may form hematite.
However, the TGA was carried out in the flow of
Table 1. XRD analysis for oil shale minerals.
Sample
1
2
3
4
5
6
7
Quartz
Kaolinite
Muscovite
Smectite
Siderite
Pyrite
Calcite
28.3
27.2
27.9
42.5
36.7
32.6
29.1
0
0.9
4.6
29.5
27.7
2.9
0
15.4
18.7
16.3
3.1
3.5
5.7
6.3
0
0
0
0
0
29.3
26.7
0.7
1.4
0.9
8.3
6.5
1.3
1.5
1.3
0.6
1.5
0.2
0
1.6
1.9
15.4
16.6
13.7
0.8
0.5
25.7
24.3
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
INVESTIGATION OF MINERAL COMPOSITION OF OIL SHALE
Table 2. Oil shale samples TGA (weight loss) for the weight loss regions.
Sample
1
2
3
4
5
6
7
20–200 ◦ C
200–400 ◦ C
400–500 ◦ C
450–600 ◦ C
200–600 ◦ C
600 ◦ C +
20–900 ◦ C
4.11
5.24
3.05
1.7
3.36
3.41
3.16
3.3
4.31
4.13
1.33
2
2.99
4.07
10.96
9.97
12.97
6.15
5.95
9.15
8.61
15.49
12.05
21.3
11.22
8.25
10
8.95
27.75
24.33
37.4
16.7
14.2
20.14
19.63
5.44
5.59
3.54
2.87
2.8
12.94
11.75
37.3
35.58
43.98
21.27
20.36
36.59
30.54
nitrogen and the pyrite will not reach the hematite stage.
The contribution to the weight loss from decomposition
of pyrite may be negligible in N2 gas. Due to kerogen
decomposition in this region, the large weight loss may
be as a result of the weight loss of the clay and other
minor minerals. Therefore, it is not possible from TGA
alone to evaluate individual mineral weight losses in
this region.
Next major phase of weight loss occurs in the temperatures between 600 and 850 ◦ C. This region is mainly
dominated by the decomposition of carbonate minerals
such as calcite, dolomite and ankerite (Table 1). Samples 6 and 7 reveal the high contents of calcite, and this
is followed by samples 1, 2 and 3. Samples 4 and 5
contain negligible amount of calcite. The siderite contents of most of the samples are negligible except in
samples 4 and 5. However, this may not make a significant contribution to the weight loss values. The weight
loss from decomposition of pyrite may be negligible.
Table 2 shows TGA weight loss at temperature ranges
of over 600 ◦ C. Samples 6 and 7 show relatively high
weight losses at temperatures over 600 ◦ C, indicating
high calcite and/or siderite contents.
Some researchers have shown that the amount of
weight loss is related to the final temperature. For
example, Skala et al .[15] showed an increase in total
weight loss with increasing temperature of pyrolysis
for Yugoslavian kerogens using TGA. A similar relationship has also been reported by Doan and Uysal[16]
for Turkish oil shale. Moroccan oil shale exhibited a
similar link between increased final pyrolysis temperature and increased weight loss, but showed an increase
in the rate of weight loss with increasing final pyrolysis
temperature.
The weight loss of mineral decomposition can be
calculated from the reaction in Eqns 1–4 below. As
the samples are oxidated, the influences of kerogen
are eliminated. According to the weight loss of TGA
(Tables 2 and 3), the content of mineral can be calculated and the results of calculation which have ignored
the affection of the minor minerals are shown in
Table 4[7] .
Smectite (Ca, K)0.65 (Al,Mg, Fe)4 (S, Al)8 O20 (OH)4
−−→ (Ca,K)0.65 (Al,Mg, Fe)4 (Si, Al)8 O22
+ 2H2 O(g)
(1)
Kaolinite Al2 Si2 O5 (OH)4 −−→ Al2 Si2 O7
+ 2H2 O(g)
(2)
Siderite (Fe,Mg)CO3 −−→ (Fe,Mg)O
+ CO2 (g)
(3)
Calcite CaCO3 −−→ CaO
+ CO2 (g)
(4)
The results of chemical method and TGA on identifying the content of carbonate are uniform (Table 5).
However, integrating with the result of XRD provides
complete mineral composition identification. The primary reason for this phenomenon is the precision of
apparatus, operate factor and tropism of flake.
Calculating the organic content
Hydrogen peroxide was used as the oxidant to oxidate
the shale samples. This operation eliminates the effect
Table 3. Oxidated oil shale samples TGA (weight loss) for the weight loss regions.
Sample
1
2
3
4
5
6
7
20–200 ◦ C
200–400 ◦ C
400–500 ◦ C
450–600 ◦ C
200–600 ◦ C
600 ◦ C +
20–900 ◦ C
2.79
3.39
3.04
1.26
2.01
5.03
5.56
0.9
1.68
1.45
1.09
1.61
1.42
2.39
2.31
2.69
2.45
3.3
3.74
3.13
3.58
2.48
2.24
2.4
3.14
3.26
2.66
4.55
4.26
4.97
4.88
5.61
6.72
5.02
8.24
0.75
0.78
0.66
1.3
2.64
4.05
2.13
6.8
9.14
8.58
8.17
11.38
14.1
15.9
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
DOI: 10.1002/apj
695
D.-M. WANG ET AL.
Asia-Pacific Journal of Chemical Engineering
Table 4. Content(w%) of oil shale minerals.
Sample
Quartz
Kaolinite
muscovite
Smectite
siderite
calcite
1
2
3
4
5
6
7
28.36
27.27
27.93
42.5
36.73
28.63
25.18
–
–
–
20.22
23.50
–
–
13.57
16.51
12.79
–
–
–
–
–
–
–
–
–
29.41
34.21
–
–
12.36
12.70
8.04
–
–
29.41
26.71
Table 5. Content(CO2 %) of carbonate in oil shale.
Sample
XRD
TGA
CM
1
2
3
4
5
6
7
7.04
5.43
5.36
7.85
5.59
5.92
6.37
3.54
3.67
3.50
2.87
3.06
2.69
2.80
2.89
11.80
12.94
12.39
11.26
11.75
11.36
CM – chemical method(GB/T 218–1996)
Table 6. Content(w%) of oil shale organic.
Sample
1
2
3
4
5
6
7
OM/w% 23.56 20.03 32.56 14.55 12.38 16.21 17.67
of organic composition in the results of TGA and makes
the quantitative analysis of mineral composition easy.
According to the weight loss of samples, a simple
method can be provided to identify the organic content
in laboratory. An equation for calculating this can be
derived from the weight changes of shale samples.
The content of organic composition can be calculated
with it.
After the shale samples were leached with hydrogen
peroxide several times, organic composition had been
oxidated completely. DRIFTS results have proved that
the peak of hydrocarbon has nearly disappeared after
being oxidated (Fig. 5). In the process of above reaction, only carbonate and some pyrite had reacted with
hydrogen peroxide. This can be testified in Fig. 4, where
the peak of pyrite near 33◦ 2θ and the peak of calcite near 30◦ 2θ have disappeared. According to the
weight changes of samples, content of organic composition could be calculated with Eqn 5[10] :
OM = [(W1 − W2 )/W1 ] − CO2 − 0.6S
(5)
where
OM - content of organic composition (w%)
W1 - weight of the original sample
W2 - weight of the oxidated sample
CO2 - dispersion of carbonate (CO2 %)
S - dispersion of pyrite(S%)
Because of the small percentages of the content of
pyrite in the oil shale samples (Table 1), the dispersion
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
7.56
7.38
–
–
of pyrite could be neglected. So, Eqn 5 can be modified
to Eqn 6:
OM = [(W1 − W2 )/W1 ] − CO2
(6)
According to Eqn 6, the content of organic composition can be calculated easily and results of the calculation are presented in Table 6. The widely used industrial
method of evaluating the oil yield from oil shale samples is the MFA[2,3] . This method is time consuming,
laborious and expensive. Large number of oil shale samples is required to be tested in order to determine the
validity and the feasibility of oil shale mining and processing. The content of organic composition in oil shale
can be identified easily in laboratory using the integration approach of DRIFTS, TGA and XRD.
When considering TGA, DRIFTS and XRD techniques alone, each technique has its own advantage,
but is unable to provide the whole picture for oil shale.
TGA results indicate the cumulative effect of kerogen
and mineral decomposition, but not the individual contribution from kerogen and each mineral. DRIFTS may
identify the hydrocarbons and indicate some group of
minerals, but evaluating total mineralogy is complex.
XRD on the other hand, provides a comprehensive picture on the mineralogy; however, it does not show the
3600
3200
2800
Sample1
Intensity/cps
696
2400
Sample2
2000
Sample3
1600
Sample4
1200
Sample5
800
Sample6
400
Sample7
0
10
20
30
40
50
60
70
80
2Theta/deg
Figure 5.
samples.
XRD scans for the seven oxidated oil shale
Asia-Pac. J. Chem. Eng. 2009; 4: 691–697
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
amorphous contents in detail. There are some errors in
the quantitative evaluation of mineral content. Integration of the XRD, DRIFTS and TGA results of the oil
shale samples from different locations have provided a
better way of mineral composition identification.
CONCLUSIONS
The mineral composition of oil shale from different
locations in China shows variation in mineral composition and kerogen content. DRIFTS results are integrated
with XRD results in identifying the inorganic mineral
composition of oil shale when it comes to inorganic
mineral contents of oil shale, especially in identifying carbonate minerals. The XRD analysis can provide
quantitative data on the crystallized content. DRIFTS
result indicated that all kerogen had been oxidated by
hydrogen peroxide and most hydrocarbons present in
the oil shale are aliphatic. Meanwhile, some minerals
could be identified. As the samples are oxidated by
hydrogen peroxide, mineral composition of oil shale
may be obtained and the influences of kerogen are eliminated in TGA. The weight loss of TGA on the content
of mineral decomposition between 20 and 900 ◦ C has
been calculated and the results are similar for almost all
the samples. There are some errors in the quantitative
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
INVESTIGATION OF MINERAL COMPOSITION OF OIL SHALE
evaluation of mineral content. Combination of DRIFTS,
XRD and TGA results that the content of mineral composition in oil shale could be identified easily. Also, a
simple method has been provided to identify the content
of organic matter in laboratory.
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DOI: 10.1002/apj
697
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