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Chemical composition of carbon disulfide-extractable fraction from oil shales of three Chinese deposits.


Rapid increase in consumption of energy and chemicals leads to dramatic increase in the prices of conventional fossil resources and thereby makes fuel chemists to pay more attention to alternative resources. Oil shales could be promising alternative ones because their reserves are large [1, 2] and hydrogen to carbon molar ratio in organic matter is high. Understanding of the composition of organic matter in oil shales is of significance not only to organic geochemistry but also to efficient utilization, especially value-added utilization of them.

Most of the related work, however, have been focused on supercritical fluid extraction, extraction yield and composition of biomarkers [3-8]. Only few researchers [9-13] have paid attention to detailed characterization of molecular structure of oil shales.

Our previous work showed that separable and non-destructive techniques are effective for determination of molecular structures of organic species present in oil shales [14], coals [15-18] and their reaction mixtures [19-21]. Because of its low boiling point and good penetrability in pores of solid fossils such as coals and oil shales, carbon disulfide ([CS.sub.2]) was used as an effective solvent for extracting aliphatic and aromatic hydrocarbons of lower molecular mass [14-18]. Using the techniques, we investigated the composition of organic species in carbon disulfide-extractable fraction (CDEF) from three Chinese oil shales.


Solvent and oil shale samples

[CS.sub.2] used as the solvent in the experiment is an analytical-pure reagent and distilled before use. GC/MS analysis shows no species in the distilled solvent except for [CS.sub.2] itself.

Oil shales (OSSs) used in the experiment were taken from the following deposits: Fushun (FS), Longkou (LK) and Huadian (HD), China, pulverized to pass through a 200-mesh screen and dried in vacuum at 80[degrees]C for 24 h before use. Table 1 shows the proximate and ultimate analyses of the OSSs.

FTIR analysis

Organic groups of OSSs were characterized using a Nicolet Magna IR-560 FTIR. The FTIR spectra were generated by collecting 50 scans at a resolution of 8 [cm.sup.-1] in reflectance mode. Measuring regions were 4000-500 [cm.sup.-1]. Figure 1 displays FTIR spectra of OSSs.


Extraction with [CS.sub.2] and analysis of the extracts using GC/MS

Each OSS was extracted with 300 mL of [CS.sub.2] under the nitrogen atmosphere in a Soxhlet extractor during at least 10 days. The extraction solution was concentrated to ca 1 mL using a rotary evaporator, and ca 0.5 [micro]L of the concentrated solution was analyzed using a Hewlett-Packard 6890/5973 GC/MS equipped with a capillary column coated with HP-5MS (30 m x 0.25 mm inner diameter (ID), film thickness of 0.25 [micro]m) and with a Hewlett-Packard 6890 GC equipped with a capillary column coated with HP-101 (30 m x 0.32 mm ID, film thickness of 0.3 [micro]m). The columns were heated at a rate of 10[degrees]C/min from 100[degrees]C (and held at the temperature for 2 min) to 300[degrees]C (and held at temperature for 5 min). Both injector and detector temperatures were set at 300[degrees]C. Mass spectra were obtained at an electron impact potential of 70 eV within a range of 30-500 amu. A series of authentic compounds purchased from Aldrich Chemical Co., Inc. was used for confirmation and quantification of the compounds identified with GC/MS. The yields (wt.%, daf) of extracts in the OSSs from FS, LK and HD were 7.1, 4.2 and 8.9, respectively.

Results and discussion

FTIR analysis of OSSs

As shown in Fig. 1 and Table 2, OSS from HD contains much more aliphatic moieties (AM) along with more carboxylic moieties than those from LK and FS. The content of free hydroxyl groups and epoxide along with aromatic moiety in the OSSs decreases in the order: FS > HD > LK. OSSs from HD and LK contain more alkenyl moiety than that from FS. There is more alkanol moiety in OSSs from FS and LK than in that from HD. Silicate content in OSSs decreases in the order: FS > HD >> LK, just being consistent with the order of their ash content.

Interestingly, a remarkable and appreciable amount of -C[H.sub.2]Br moiety can be observed in FTIR spectra of OSSs from FS and HD, but no organobromines were detected in CDEFs from FS and HD using GC/MS, implying that the -C[H.sub.2]Br moiety in both OSS may exist as organic macromolecular species.

GC/MS analysis

Figure 2 shows total ion chromatograms (TICs) of all CDEFs. The compounds identified fall into the following categories: normal alkanes (NAs), isoprenoids (IPs), cyclanes, alkenes, alkylated arenes (AAs) and organo-oxygen compounds (OOCs), as listed in Tables 3 to 8, respectively.

Organic compounds (OCs) identified in CDEFs account for 15.12% from FS, 13.75% from HD and 7.34% from LK, suggesting that OCs identified in CDEFs are only a minority, and majority of CDEFs may consist of macromolecular and/or strongly polar species, which cannot be detected with GC/MS.


As shown in Figs. 3-5, alkanes are predominant in all CDEFs, and NAs are main components detected in CDEFs from HD and LK. The amounts of alkenes detected in CDEF from LK were much larger than those in CDEFs from HD and LK. The total yield of AAs in CDEF from FS is higher than that in CDEF from LK, while no AAs were observed in CDEF from HD. The total yield of OOCs detected in CDEF from HD is higher than that in those from FS and LK.




As Fig. 6 illustrates, cyclanes and NAs are the largest group components in CDEFs from FS and LK respectively, whereas NAs are predominant in CDEF from HD.


NAs. In total, seventeen NAs, from [C.sub.16] to [C.sub.33], were detected in CDEFs (Table 3), and all NAs were observed in CDEF from HD (Fig. 2c). Most of compounds detected are NAs, and heptacosane is predominantly abundant as a single compound in CDEF from HD. NAs are also primary components in CDEF from LK (Fig. 2b), but secondary ones in CDEF from FS (Fig. 2a). Much lower concentration of NAs with carbon number below 20 in CDEFs indicates that catalytic hydrocracking is necessary for converting the extracts to a clean liquid fuel.

IPs. In total, five IPs, from [C.sub.15] to [C.sub.20], were detected in CDEFs (Table 4) and all IPs were observed from CDEF from FS (Fig. 2a). Pristane and phytane predominate in IPs, being the only two IPs in CDEF from LK, while pristane is the only IP detected in CDEF from HD.

Cyclanes. Totally twenty five cyclanes were identified in CDEFs (Table 5), including two bicyclic sesquiterpanes, six cholestanes, sixteen hopanes in addition to 17[beta]H,21[alpha]H-normoretane. Twenty one of them were observed in CDEF from FS (Fig. 2a) and 17[alpha]H-22,29,30-trisnorhopane and 17[alpha]H,21[beta]H-hopane are predominantly abundant, while only five cyclanes were found in CDEF from LK (Fig. 2b), 17[beta]H,21[beta]H-30-norhopane being the most abundant one. As a possible product at thermolysis of pentacyclic triterpanes [22], 8,14-seco-hopane was detected only in CDEF from LK. The number of cyclanes detected in CDEF from HD is also five, but all the cyclanes differ from those detected in CDEF from LK and their concentration is much lower.

Alkenes. In all, five alkenes were identified in CDEFs (Table 6), including three hopenes and two disasterenes. All five were detected in CDEF from LK (Fig. 2b) and 30-norneohop-13(18)-ene was detected in CDEF from HD. Noteworthily, 30-norneohop-17(21)-ene is the most abundant compound in CDEF from LK. Only one alkene occurs in CDEF from HD (Fig. 2c) except for 30-norneohop-13(18)-ene.

AAs. Totally five AAs were detected (Table 7), including alkyl-substituted tetralins (peaks 4 and 8), naphthalene (peak 12) and diphenylmethane (peak 22) along with a sterane (peak 31). All of them appear in CDEF from FS (Fig. 2a) and one in CDEF from LK (Fig. 2b), but there is no AA in CDEF from HD. The concentration of all the AAs detected is low.

OOCs. In all, five OOCs were detected in CDEFs (Table 8), including a phenol (peak 7), two esters (peaks 9 and 18), an alkanone (peak 15) and an alkanoic acid (peak 21). Both esters appear in all CDEFs, and the alkanone was detected in CDEFs from both LK and HD.


The yield (wt.%, daf) of extract and the share of GC/MS-detectable species in the OSS from LK are lower than corresponding characteristics of samples from FS and HD. [CS.sub.2]-extractable fractions of three Chinese oil shales mainly consist of alkanes along with small amounts of alkenes, aromatic ring- and oxygen-containing compounds. Large amounts of NAs and cyclanes along with small amounts of IPs, alkenes, AAs and OOCs are detected in CDEF from FS. OCs detected in CDEF from LK mainly consist of NAs and alkenes, in which 30-norneohop-17(21)-ene is the most abundant compound. NAs (from [C.sub.16] to [C.sub.33]) are predominant in CDEF from HD, whereas no AAs are observed in this extract. The amount of OOCs detected in CDEF from HD is much greater than those in extracts from FS and LK.


This work was subsidized by the Special Fund for Major State Basic Research Project (Project 2004CB217801).

Presented by Qian Jialin

Received January 11, 2007


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(a) School of Chemical Engineering China University of Mining and Technology Xuzhou 221008, Jiangsu, China

(b) Institute of Coal Chemical Engineering Dalian University of Technology Dalian 116012, Liaoning, China

(c) School of Resources and Environmental Engineering Heilongjiang Institute of Science and Technology Harbin 150027, Heilongjiang, China

* Corresponding author: e-mail,
Table 1. Proximate and ultimate analyses (wt.%) of OSSs *

                        Proximate analysis
Oil shale
deposit       []    []    [V.sub.daf]

Fushun             2.1          76.1           88.5
Longkou           11.6          35.0           59.7
Huadian            7.8          60.8           86.0

                Ultimate analysis (daf)
Oil shale                                  [S.sub.t,d],
deposit         C          H         N         wt.%

Fushun         42.1       8.8       2.1        2.6
Longkou        76.1       7.5       0.4        2.4
Huadian        66.2      10.4       1.3        3.3

* Data for proximate and ultimate analyses were obtained with Leco
Mac-400 Thermogravimetric Analyzer, Leco CHN-2000 Elemental
Determinator and Leco SC-132 Sulfur Determinator, respectively.

Table 2. Structural features of OSSs characterized by FTIR

  Wavenumber,                                          Oil shale
   [cm.sup.-1]                   Assignment              Fushun

3692, 3651, 3621                 -OH (free)                S
      3432                      -OH (bonded)               S
2919, 2852, 1435         [MATHEMATICAL EXPRESSION          S
                         NOT REPRODUCIBLE IN ASCII]
      1705                         -COOH                   VW
      1629                         >C=C<                   O
      1096                    >C-OH (alcohols)             VS
    1029, 461                    Silicates                 VS
       906                        Epoxide                  S
    789, 686         C-H (m-disubstituted benzene) (Obv)   S
       538                     -C[H.sub.2]Br               VS

  Wavenumber,             Oil shale
   [cm.sup.-1]       Huadian     Longkou

3692, 3651, 3621     O             VW
      3432           S             S
2919, 2852, 1435     VS            S
      1705           W             VW
      1629           S             S
      1096           VS            VS
    1029, 461        VS            VS
       906           S             N
    789, 686         O             O
       538           VS            VW

VS: very strong; S: strong; O: ordinary; W: weak; VW: very weak;
N: none; Obv: Out-of-plane bending vibration

Table 3. Yields of NAs detected in CDEFs

                               Yield, [micro]g/g OSS, daf

No.    Compound             Fushun     Longkou     Huadian

  6    Hexadecane                                   119.8
 13    Octadecane                                   169.3
 16    Nonadecane            83.2                   129.7
 17    Eicosane              80.5                   110.8
 19    Heneicosane          157.1        47.1       265.1
 20    Docosane             221.2        65.5       327.4
 23    Tricosane            472.3       170.9       781.7
 24    Tetracosane          362.8        89.6       428.4
 25    Pentacosane          513.8       116.7       997.3
 26    Hexacosane           485.0       198.1       663.6
 27    Heptacosane          575.5       279.6      2628.1
 30    Octacosane           303.5       152.8       537.8
 33    Nonacosane           358.6       212.6       993.5
 37    Triacontane           87.9        48.4       297.9
 42    Hentriacontane       127.8                   480.3
 46    Dotriacontane                                191.1
 54    Tritriacontane                               221.8

Table 4. Yields of IPs detected in CDEFs

                                        Yield, [micro]g/g OSS, daf

No.    Compound                        Fushun    Longkou    Huadian

  3    2,6,10-Trimethyldodecane        102.5
  5    2,6,10-Trimethyltridecane       162.5
 10    2,6,10-Trimethylpentadecane     155.5
 11    Pristane                        723.1      119.7      330.1
 14    Phytane                         502.8       60.5

Table 5. Yields of cyclanes detected in CDEFs

                                            Yield, [micro]g/g OSS, daf

No.   Compound                                   Fushun

 1    [C.sub.13]-bicyclic sesquiterpane
 2    [C.sub.14]-bicyclic sesquiterpane           217.6
34    Cholestane                                  133.6
35    18[alpha]H-22,29,30-Trisnorneohopane        205.7
36    14[alpha]-Methylcholestane                   21.4
38    17[alpha]H-22,29,30-Trisnorhopane           305.9
39    24-Methyl-5[alpha]H-cholestane               89.4
40    17[beta]H-22,29,30-Trisnorhopane             81.1
41    24-Ethyl-5[beta]H-Cholestane                 81.9
43    8,14-seco-Hopane
44    24-Ethyl-5[alpha]H-Cholestane                85.9
48    17[alpha]H,21[beta]H-30-Norhopane           523.0
49    17[beta]H,21[beta]H-30-Norhopane            181.3
50    17[beta]H,21[alpha]H-Normoretane
51    Trimethylcholestane                         194.0
52    17[alpha]H,21[beta]H-Hopane                 873.1
53    17[alpha]H,21[beta]H-Hopane                 150.3
55    17[alpha]H,21[beta]H-22S-Homohopane         181.8
56    17[alpha]H,21[beta]H-22R-Homohopane         182.4
57    17[beta]H,21[alpha]H-Hopane
58    17[beta]H,21[alpha]H-Homohopane             108.1
59    17[alpha]H,21[beta]H-22S-Bishomohopane       99.1
60    17[alpha]H,21[beta]H-22R-Bishomohopane      101.6
61    17[alpha]H,21[beta]H-22S-Trishomohopane      73.5
62    17[alpha]H,21[beta]H-22R-Trishomohopane      61.3

      Yield, [micro]g/g OSS, daf

No.   Longkou        Huadian

35     59.2
40                    251.3
43                     63.4
48     61.4
49     70.3
50                    216.3
52     77.9
55                     99.9
57                     95.4
58                    182.2

Table 6. Yields of alkenes detected in all CDEFs

                                         Yield, [micro]g/g OSS, daf
No.    Compound
                                         Longkou     Huadian

28     Hopene                                91.1
29     24S-Ethyl disaster-13(17)-ene         80.7
32     24R-Ethyl disaster-13(17)-ene         96.6
45     30-Norneohop-17(21)-ene                414       277.1
47     30-Norneohop-13(18)-ene              180.4       122.4

Table 7. Yields of ASAs detected in CDEFs

                                          Yield, [micro]g/g OSS, daf

No.    Compound                              Fushun      Longkou

  4    1,1,6-Trimethyltetralin               125.8
  8    5,6,7,8-Tetramethyltetralin           169.3
 12    Cadalene                               84.4
 22    1,1'-Di(2,3-xylyl)ethane              212.1
 31    [C.sub.27]-Monoaromatic sterane       166.8        95.6

Table 8. Yields of OOCs detected in the CDEFs

                                           Yield, [micro]g/g OSS, daf

No.   Compound                             Fushun    Longkou    Huadian

 7    3-Methyl-1,5-di(tert-butyl)phenol      81.1
 9    BTMPMM                                244.0       65.1      211.4
15    6,10,14-Trimethyl-2-pentadecanone                 57.7      173.9
18    Isopropyl palmitate                    80.7      108.6      301.7
21    Stearic acid                                                631.8
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Author:Cao, Jing-Pei; Zong, Zhi-Min; Zhao, Xiao-Yan; Liu, Guang-Feng; Mou, Jie; Wang, Feng; Huang, Yao-Guo;
Publication:Oil Shale
Date:Sep 1, 2007
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