Diterpanes, triterpanes, steranes and aromatic hydrocarbons in natural bitumens and pyrolysates from different mimic coals

Gaxhimica Copyright

0016-7037/92/65.00 + .oO

Acta Vol.56, pp. 2761-2788 Pergamon PressLtd.Printed in U.S.A.

er Cosmochimica Q 1992

Diterpanes, triterpanes, steranes, and aromatic hydrocarbons in natural bitumens and pyrolysates from different humic coals* SHAN-TAN Lu Is2and ISAAC R. KAPLAN’ ‘Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90024-l 567, USA *Global Geochemistry Corporation, 69 19 Eton Avenue, Canoga Park, California 9 1303-2194, USA (Received October 23, 1990; accepted in revisedform April 23, 1992)

Abstract-There is a significant difference in the distribution of terpanes in natural bitumen extracted from four coals identified as Rocky Mountain coal (RMC), Australian Gippsland L&robe Eocene coal (GEC) , Australian Gippsland Latrobe Cretaceous coal (GCC) , and Texas Wilcox lignite ( WL) . Whereas pentacyclic triterpanes are dominant in GEC, GCC, and WL, diterpanes strongly predominate in the bitumen of RMC. This indicates that resin is a more important constituent of RMC than in the other coals and releases the diterpenoids at an early stage of diagenesis. Furthermore, the composition of diterpanes is also different among these coals. For example, tricyclic diterpanes are the only diterpanes present in RMC, whereas tetracyclic and tricyclic diterpanes are both present in GEC and GCC, and tetracyclic diterpanes are most abundant in GEC. However, diterpanes are nearly absent in WL. Surprisingly, the diterpenoid content is negligible in the pyrolysates of all coals. The sterane and triterpane distributions in the natural bitumen of coals are very different from those in pyrolysates. C,, cu/322R hopane predominates in the m/z 191 mass fragmentograms of the natural bitumens, whereas a homologous series of hopanes ( C2+& ; except Cz8) is present in the coal pyrolysates. C29 steranes dominate in all of the coal bitumens as well as pyrolysates. Cl7 steranes are absent in the natural bitumen, but are generated in pyrolysates during lengthy heating of coal kerogen. This indicates that formation of secondary steranes occurs by cracking the side chain. Cs9 monoaromatic steroid hydrocarbons are abundant in the natural bitumen of the four coals. The m/z 253 distribution is similar for GEC, RMC, and WL, but it differs from the more mature GGC, which has a lower content of 20R of both 5a and 5B Cz9 MA-steroids. Triaromatic steroid hydrocarbons are only present in GCC, whereas significant amounts of tetra- and triaromatic triterpenoid hydrocarbons are present in the other three coals (GEC, RMC, and WL). The ratio of benzo( e)pyrene/perylene may be potentially useful as a maturity parameter because the amount of benzo(e)pyrene increases with thermal stress, whereas perylene decreases with heating time. Benzohopanes are widely present in four humic coals but become unstable after 10 h heating at 300°C.

coal, Lu et al. ( 1989) suggested that the rate of isomerization of these biomarkers is influenced by the rate of generation of biomarker compounds from kerogen and the rate of thermal degradation of the steranes and triterpanes. They observed that generation and isomerization are more significant in the short-term (2-100 h at 300°C) pyrolysis, whereas thermal destruction becomes more important in the longterm ( 100-1000 h) pyrolysis. In the study we describe here, the key biomarker ratios are also compared with the vitrinite reflectance of unheated coal kerogen and the residual kerogen after pyrolysis. The composition of diterpanes was also investigated, because they have been proposed as markers of higher plant material in sediments, coals, and crude oils ( SIMONEIT,1977; BARRrCKand HEDGES, 1981; PHILPet al., 1981, 1983; RICHARDSONand MILLER, 1982; LIVSEYet al., 1984; NOBLE et al., 1985, 1986; VENKATESANet al., 1986). NOBLE et al. ( 1985) suggested that the most likely natural precursors for the tetracyclic diterpanes are tetracyclic diterpenes which are present in the leaf resin of conifers. Recently, WESTONet al. ( 1989) identified the diterpanes (tri- and tetra-) in oils from the Taranaki Basin of New Zealand which had the same structure as those occurring in extant trees of the Araucariaceae and Podocarpaceae family. They suggested that coal

INTRODUCIION THE DISTRIBUTIONOFTRITERPANESIN coals has been widely studied by GULYAEVAet al. ( 1982), VOROBIEVA et al. ( 1983), HOFFMANN et al. ( 1984), ALEXANDERet al. ( 1985 ), Lu (1987), and LU et al. ( 1989). However, reports on the study of steranes in coals ( HOFFMANNet al., 1984, ALEXANDERet al., 1985; LU et al., 1989) are rather scant, probably because the concentration of steranes in coals is low. The distribution of triterpanes and steranes in the natural bitumens of unheated coals and pyrolysates from heating of four different humic coals are described in this report. The isomerization of biomarker epimers such as 20s + 20R C& sterane and 22s + 22R homohopanes have been previously studied and employed as molecular maturation indices by MACKENZIEet al. ( 1980)) MACKENZIE( 1984 ) , and SEIFERT andMo~Dow~~( 1978,1986). TheS/Rratiosincreasewith thermal maturation or burial depth and reach a steady state near the peak of oil generation (MACKENZIE, 1984). However, based on the results from anhydrous pyrolyses of both an immature Cretaceous black shale and a Rocky Mountain * Institute of Geophysics and Planetary Physics Contribution No. 3334. 2761

S.-T. Lu and I. R. Kaplan

2762

measures may have formed from these trees and were probably the sources of diterpanes. Pentacyclic triterpenoid compounds often are major constituent of higher plant waxes and coals, and are believed to be important source materials for aromatic hydrocarbons in ancient sediments and petroleum ( BENDORAITIS,1973). A search and description of aromatic steroids, aromatic triterpenoids and other polycyclic aromatic hydrocarbons were also made on the natural bitumens and pyrolysates of the four coals. These aromatic components of coal extracts have been reported previously (WHITE and LEE, 1980; CHAFFEE and JOHNS, 1983; Fu et al., 1986). This paper aims to extend the understanding of the formation, aromatization, and degradation of saturate and aromatic hydrocarbons generated in the coalification process by comparing their relative abundance among natural bitumens and their pyrolysates.

EXPERIMENTAL Four different humic coals were used for this study. The Eocene and Cretaceous I&robe coals (GEC and GCC ) were cored from the margin of offshore Gippsland basin. The vitrinite reflectance (Ro) for these two coals is listed on Table 1. Rocky Mountain coal is from the Late Cretaceous Mesa Verde coal measures of Hanna Basin, southeastern Wyoming. The Wilcox lignite (WL; brown coal) was obtained from the Eocene Wilcox Group in east-central Texas. A detailed compositional description of these four coals is given in Lu and KAPLAN ( 1990). The coals were extracted in a Soxhlet extraction system with a mixture of 9: 1(v/v) dichloromethane/methanol for 48 h. A mixture of 2:l (v/v) hydrofluoric acid and hydrochloric acid was used to

remove the mineral matrix. Humic and fulvic acids were extracted following deminerahzation. Experimental details are given in Lu ( 1987). The coal kerogen was sealed in Pyrex tubes under vacuum and pyrolyzed without the addition of water at a temperature of 300°C for 2-1000 hours. The pyrolysates were extracted with a Soxhlet extraction system as before and the vitrinite reflectance was measured on the residual coal kerogens. The ahphatic hydrocarbon fraction was separated by column chromatography on silica gel using n-hexane as an eluant. n-alkanes were removed by 5 A molecular sieve. X/MS analysis of branched and cyclic ahphatic hydrocarbons was carried out using a Finnigan 9610 gas chromatograph directly linked to a Finn&m 4000 quadrupole mass spectrometer (electron energy-70 eV, ion source27O’C). Separations were performed on a 30 m DB-5 0.25 mm fused silica capillary column. The 9610 gas chromatograph was programmed in the following manner: initial temperature at 35°C held isothermal for 6 min; temperature programming at 4”C/min to 280°C t”C/min to 310°C; isothermal at 310°C for 15 min. Samples were injected at 280°C in a splitless mode. Mass spectral data were stored and processed with a Finnigan INCOS 2300 data system. Tricyclic and tetracyclic terpanes were tentatively identified by comparing their retention time and mass spectra with published data (NOBLE et al., 1985, 1986; PHILP, 1985; WESTON et al., 1989). The GC/MS analysis of the aromatic fractions were conducted at Global Geochemistry Corporation. Gas chromatography-mass spectrometry was also carried out on a Finnigan 96 10 gas chromatograph connected to a Finnigan 4000 quadrupole mass spectrometer. Gas chromatography was completed using a 60 m DB-I 0.25 mm fused silica capillary column and programmed for 135” to 320°C at 2”C/ min; isothermal at 320°C for 20 min. Full scan GC/MS analyses were conducted on ah aromatic fractions in the electron impact mode at 70 eV. Multiple ion detection (MID) analyses was also conducted on selected samples. Data from MID analyses were examined primarily using m/z 253 (monoaromatic steroids) and m/z 23 1 (triaromatic steroids). Compound identification was based on their retention time and mass spectra and compared with published data

Table 1: Steraneand niterpaneratios for pyrolysatesgeneratedfrom varioushumic coal kerogensat 3CVC.

%

F&K

Kemgen

0 2 hours 10

B!L Kemgen

C31 aP

C32 ‘#

0.14 0.16 0.40 0.50

0.22 0.15 0.36 0.50

0.42 0.60 1.91 3.18

0.26 0.40 0.56 0.59

0.30 0.35 0.55 0.56

2.96 4.69 10.32 *+

i.14 0.18 0.32 0.51

0.34 0.37 0.42 0.66 0.75

Ll8 0.25 0.59 0.61

0 2 hours 10 100 loo0

0.59

0.48 0.43 0.43 0.49 ___1

0.58 0.51 0.50 0.56 0.59

0.59 0.50 0.48 0.57 0.59

0 2 hours

0.32

LO 0.12 0.23 0.71

0.01 0.10 0.12 0.29 0.54

--- * 0.13 0.13 0.25 0.56

0 2 hours 1: loo0

Qx Kemgen

c29

0.50 0.45 0.61 0.84 1.20

lA! s!!z Kemgen

C29 aaa

1: 1000

0.30 0.33 0.39 0.55

C27

0.09 0.29 0.49 1.46 11.25

RMC = RockyMountaincoal;GEC = GippslandEocene coal; GCC = GippslandCretaceouscoal, WL. = Wilcox lignite; 0 = original extract(bitumen); * = not present;t 176 not present.

2163

Aromatic hydrocarbons in different coals ( MOLIXDWAN and FAGO,1986; LEWAN et al., 1986;LAFLAMME and HITES,1979; CHAFFEE and JOHNS,1983). The presence of benzo-

Table2: Trimpaneidentification.

fluoranthene, benzopyrene, and perylene polycyclic aromatic hydrocarbons was confirmed by coinjection and mass spectra correlation using a synthetic reference sample provided by Dr. M. I. Venkatesan.

RESULTS AND DISCUSSION Biomarker Distribution in the Original Bitumens Rocky Mountain Coal (RAE) The distribution of steranes and hopanes in this coal ( LU et al., 1989) is unusually simple; Cs, cuj322R hopane comprises more than 90% ofthe hopanes (Fig. 1; Table 2). Other

0

original extract

2

hrs.

10 hrs.

1

7+0

100 hrs.

1000 hrs. i

7+8

J,‘w 9lo

Scan

12

1314

15

number

FIG. 1. Mass fragmentograms of triterpanes (m/z I9 1) obtained for the natural bitumen and pyrolysates of kerogen from Rocky Mountain coal (after Lu et al., 1989, Fig. 6).

1. 18a(H)-uisnorhopane

C27H46

2.

llla(H)-uisnorhopane

c27%6

3.

17~(H)-aisnorhopane

c27&6

4.

17a(H),21P(H)-30_norhopanc

C29H50

5.

17p(H)Jla(H)-3O-no-tane

C29H50

6.

I’la(H),Zl~(H)-hopane

C30H52

7.

17fi(H),21~(H)-30-norhopoPane

C29H50

8.

17~(H),2la(H)-moretanc

c3OH52

9.

17a(H),21~(H)-3O-homohopmohopane (22.5)

C31H54

(22R) 10. 17a(H),21B(H)-30-homohopsne

Cd54

11. l’l~(H),Zl@)-hopane

c3OH52

12. 17f3(H),2la(H)-homohopanc

C31H54

13. 17a(H),21~(H)-30,3l-bishomohopane (22.9

C32H5.5

14. 17a(H),21~(H)-30,3l-bishomohopane (22R)

C32H56

1.5. 17P(H),21a(H)-30,31&shomomoretane

c32H56

16. 17p(H),21~(H)-30_homohopane

C31H54

components, such as the &3 isomer of C29 to C32 hopanes, and /3cu,a$ hopanes are found in relatively small amounts. The predominance of Cs, a@ 22R hopane was also observed in earlier studies. For example, PHILP and GILBERT ( 1984) detected the dominance of Cs, c@22R and 22s in the bitumen of coal. QUIRK et al. ( 1984) also found this component in decaying moss. An explanation for the dominance of this hopane was given by ROHMER et al. ( 1980) who suggested that its formation is probably microbial rather than chemical alteration of the moss, and that the hopane forms at very early stages of diagenesis. The Cz9 steranes ( CZ9(YCX(T 20R and C29 cwj3p20R) are the dominant steranes in the extract of RMC ( LU et al., 1989). A small amount of Cz8 (Y(Y(Y 20R is also present. There are no detectable C2, steranes in the extract. Furthermore, the CZ9diaster-13( 17)-enes, with a base peak of m/z 257, are more abundant than the regular C29 steranes, but no rearranged sterenes of Cz7 and Czs were detected. This indicates that terrestrial higher plants dominated the precursors of the organic matter of the coal ( HUANG and MEINSCHEIN, 1979; MOLDOWANet al., 1985 ). MACKENZIEet al. ( 1982) suggested that higher plant input should also be reflected by a high hopanoidfsteroid ratio (>5). The ratio of hopane jsterane (i.e., Cso 17a(H), 21/3(H) hopane/Cz9 steranes ((YCYCY 20 (R + S) + &3/3(R + S)) is about 27.2, which further supports the view that tetigenous higher plants were predominant in the depositional setting of the RMC, although the magnitude of the ratio could also have been increased by the rearrangement of the coal biomarkers by bacteria ( HOFFMANN et al., 1984). Tricyclic diterpenoids are the dominant components in the C12+branched and cyclic aliphatic hydrocarbon fraction, as evident from the Reconstructed Ion Chromatogram (RIC Fig. 2). This suggests that resinite was an important com-

2764

S.-T. Lu and I. R. Kaplan

RIC

Scan Number FIG. 2. RIC of n-alkane free aliphatic fraction in the natural bitumen extracted from Rocky Mountain coal showing high content of diterpenoids.

ponent in the precursor organic matter of the RMC. Diterpenoids are often released at an early stage of resinite diagenesis ( SNOWDON, 1980; SNOWDONand POWELL, 1982 ). Figure 3 shows a m/z 123 mass fragmentogram obtained from analysis of the branched and cyclic alkanes of the RMC. The peaks labeled (a) to (j ) in this fragmentogram represent seven diterpenoid hydrocarbons (Table 3). The dominant peak (e) contains a molecular ion of m/z 262 ( Cr9HJ4, Ap pendix), and was identified as norpimarane (I) through a library search of spectra. Peaks (a) and (c) also have similar spectra as peak (e), and are probably different isomers of norpimarane. Peaks(b) and (d) were identified as C,g-tricyclic diterpane (II). The (gb) peak was identified as fichtelite (IV) with m/z 262 (C19H34) (Appendix). The appearance of an m/z 241 ion (M+ -29) shows that diterpanes (h) and (j) contain an ethyl substituent. They exhibit a molecular ion at m/z 276 ( CZOHr6)and are identified as isopimarane (V) and abietane (VI), respectively (Appendix). All the identified diterpenoid hydrocarbons in RMC are thus tricyclic diterpanes. Australian Gippsland Latrobe Eocene Coal (GEC) 2 17 of bitumen of (Fig. 4; 4) is reminiscent of a sterane distribution. Mass of most the peaks not corto steroids rather to triterpenes are present to the maturity (rank) the coal. (Y(Y(Y 20R is the sterane present the coal. addition, the of sterane this coal very low to hopane for that a meaningful ratio cannot determined. This reflects high input The

terrigenous organic matter et al., and indicates Cz, or sterols were or in abundance the initially deposited debris. Of is the predominance Cr, crj3 hopane (Fig. ) in m/z 19 mass also occurs the bitumen RMC. In addition, significant amount of unsaturated triterpenes present in extract of coal. It important to that only small amounts BB-hopanes, C&X3,, were observed, though this is less than RMC. the latter, hopanes are in the bitumen extracts pyrolysates of shorter heating ( 10 hs) . The relative concentration of diterpenoid hydrocarbons in GEC is lower than that in RMC, and the composition of diterpanes is quite different from that observed in RMC. In GEC, the amount of tetracyclic and tricyclic diterpanes are nearly equal, whereas in RMC only tricyclic diterpanes were identified. Figure 3 shows the m/z 123 mass fragmentogram in GEC. The peaks labeled (c), (f), (h), and(j) are tricyclic diterpanes, with characteristic ions at m/z 262, 276, 233, and 247, whereas (pa), (i), (k), (1), and(m) are tetracyclic diterpanes, which are characterized by m/z 189,231 (or 245), 259, 274 (Appendix). The tetracyclic diterpanes were identified with published data (NOBLE et al., 1985) as follows: ent-beyerane (ga, III), 16/3-phyllocladane (i, VIb), ent-16@kaurane (k, VIIIb), 16ru-phyllocladane (1, Via), and ent- 16arkaurane (m, VIIIa). They are similar to diterpanes identified in Australian coals or crude oils. NOBLE et al. ( 1985) concluded that these tetracyclic diterpanes are derived from tetracyclic diterpene hydrocarbons which are present in the leaf resins of conifers. For example, Cm tetracyclic diterpenes, which occur commonly in the leaf resin of conifers, are the

Aromatic hydrocarbons in different coals Rocky Mountain

2765

Coal 1623 e

10&0-

I

E

.I

1591

I

d 15_bb ,““I”“I”“I”“,““1

h 1653

1676

gb

Australian

Gippsland

Eocene Coal

Australian

Gippsland

Cretaceous

Coal

1600

Scan Number FIG.

3. Mass fragmentograms diterpanes (m/z 123) obtained from the natural bitumen of Rocky Mountain coal

and Australian Gippsland

Eocene coal.

most likely precursor of phyllocladane, kaurane, and beyerane, and the 17-nortetracyclic diterpane is probably derived from a CzOcompound by a diagenetic or catagenetic chemical reaction.

Table3: Ditapancidmtitimim a.

Napimame

b. Clpuicyclicdireqmc e.

Napimaranc

d. C@ricyclicdita~+~~~ c.

Ncqimannc

f.

c&ricyclicditcrpanc

ga. sat-beyaane gb. Rchklite h. lsqbwane i.

16EphyUocl&ne

j.

At&me

k. a-16Ekaumne 1.

16a-phyuocwe

m. a-16a-kaurane

Australian Gippsland Latrobe Cretaceous Coal (GCC) The other Australian coal is the Cretaceous Latrobe coal, which is at an early maturity stage with R,, = 0.52%. The distribution of steranes in this coal is quite different from that of the GEC (& = 0.37%). In addition to the higher plant derived Cz9 steranes, the rearranged steranes are more significant in the natural bitumen than in pyrolysates, as previously reported ( SEIFERT,1978 ) . The following rearranged steranes, Cz9 13ar, 17@,20 R and S, Czs 13~ 178 20 R and S, Cz9 I 3u, l7&20 R and S; and C28 I3j3,17a, 20 R and S; were observed in the original bitumen (Fig. 6). However, the C1, sterane is absent in extracts of both Australian coals (GEC and GCC), indicating that the source of organic matter was dominated by terrigenous input from higher plants. Furthermore, the ratio of C, aaa 20 S/S + R is about 0.48, which, according to the criteria established by MACKENZIE ( 1984), indicates that the coal is moderately mature if the bitumen is assumed to be indigenous. However, the possibility that some portion of the bitumen migrated from a deeper formation can not be overlooked. As previously observed in the extracts of RMC and GEC, CJ, arfl22 S + R is dominant in the original bitumen (Fig.

S.-T. Lu and I. R. Kaplan

2166

GIPPSLAND

EOCENE

COAL

KEROGEN

I

Wilcox Lignite from Texas Gulf Coast ( WL) This coal is the most immature of the four studied here. For example, the distribution patterns of the m/z 2 17 mass fragmentograms show no characteristic steranes (Fig. 8); they are more similar to those obtained for the original bitumen of GEC, and also to those determined in Indonesia Kalimantan oils ( HOFFMANNet al., 1984). The 22R isomer of the Cs, a/3 hopane is the major homologue in the lignite, similar to that observed in the extracts of RMC and GEC (Fig. 9). With the exception of C3, a/l 22R hopane, the distribution of hopanes is dominated by the biological /!?&hopanes with some triterpenes. Thermally mature aj3 hopanes, except for Cs, aj3 22R, are present only in trace amounts in the natural bitumen. This indicates that the a@ hopanes have not started to form in significant amounts in the lignite stage of coal. The near absence of diterpenoid hydrocarbons in WL is probably due to its immaturity which is also supported by the fact that only trace amounts of n-alkanes are present in the aliphatic fraction of the bitumen. An alternative explanation is that input of resinite was not important during deposition of the plant material.

Ii;

c E

Table 4: Stcmte ida~tiFtcation. A. Sa(H)&la(H),17a(H)-stnane

L 1900

c27Hss

Sa(H).14~(H),17~(H) 2OR-stemne

C27H48

C. 5a(I-l),14~(H),17@(H) 2OS-stersnc.

c27ti8

B. 1950

2ooa

2050

2100

2150

2200

2250

2300

Scan Number

FIG. 4. Mass hagrnentograms of.steranes(m/z 217) obtained from the natural bitumen and pyrolysates of GEC kerogen (300°C).

@OS) +

S~(H),14a(H),17a(H) 2OR-stmme

D. 5a(H).14a(H),17a(H)-sterane E. F.

@OR)

c27H48

2rl-mcthyl-Sa(H),l4a(H).17a(H)-stcranc

(20s)

CZSH50

24-methyl-l4~(H).17~H) ZOR-smme + 24-cthyl-SO(H),14a(H),17a(H) 2OS-stcrane+

7 ) . The difference between the two Gippsland Latrobe coals is that Cs, a/3 22R predominates in the GEC, whereas CsI a/3 22s is greater than the 22R isomer in the GCC, reflecting its higher maturity. It should be noticed that the biological configurations, e.g., &I hopanes and triterpenes, are not present in this original bitumen, whereas GEC still contains a significant amount of these immature compounds. This is attributed to GGCs moderate maturity, where all relatively unstable forms have been converted to /3a and a/3 by isomerization. In addition, the a/3 hopanes dominate the pa hopanes in the range of Cz7 to CJ5, (except Czs hopane), which again confirms that the coal is at a moderately mature level. The ratio of CM (a/3/a@ + @a) is about 0.85, indicating that it has reached the early stages of oil generation ( SEIFERT and MOLDOWAN,1980). The distribution of diterpanes is slightly different from that in GEC where the relative amount of the tricyclic diterpanes is higher than that of the tetracyclic diterpanes. This may reflect a difference in higher plant input during the Eocene and Cretaceous depositional events. The alternative explanation is that tetracyclic diterpanes are relatively unstable and easier to degrade to small saturated hydrocarbons which may have occurred in the more mature GCC.

24-methyl-14a(H),17a(H) 2OR-stetme G. 24-mcthy1-14@(H),17@0

zos-sterme

H. 24-mcthyl-5a(H),14a(H),17a(H) I. 24-cthyl-5a(H).14a(H), J.

K.

C2SH50

2OR-stetme

17a(H) 2OS-stemne

24-ethyMg(H),14a(H),l7a(li)

UIR-stemte +

24-ahyl-5a(H).14B(H),l7~~

2OR-stemx

24-ethyl-5a(H). 14p(H),17p (I+) ZOS-sterme

L. 24-ethyl-5a(H).14a(H),17a(H)

CzsH50

ZOR-stcrane

M. C30 stcrme

'ASH52 C29H52

C29H52 C29H52 C29H52 C30H54

N.

13fl(H),17a(H)-diasterane (20.9

c27H48

0.

13~(H),17a(H)-diast

C27H48

(2OR)

P.

24-methyl-l3fl(H).17a@IMiastcmnc (20.9)

C28H50

Q.

24-methyl-13f1(H).17a(H)-di(~>dirstersne @OR)

CZSH50

R. 24-mcthyl-l3a(H),17B(H)-diast

(20.9)

C2sH50

S. 24-ethyl-13p(H),17a(H)-diastemne (209

C29H52

T.

24-mthyl-l3a(H),17B(H)-diast

C2SH50

U.

24-ethyl-13~(H),17a(HMiastcmne @OR)

@OR)

C29H52

V. 24-ethyl-13a(H),17@)diastcrane

(20s)

C29H52

W. 24-ethyl-13a(H),17~(H)diastemte

(2OR)

C29H52

Aromatic hydrocarbons in different coals

2767

another maturation index (SEIFERTand MOLDOWAN,1978), also increases with progressive heating. Surprisingly, there are only trace amounts of diterpanes present (which were abundant in the original bitumen of RMC) in the pyrolysates (2-10h)andabsentinotherpyrolysates(1OO-1OOOh).This suggests that the resinite precursor of the diterpenoid may have been extracted with the natural bitumen during the kerogen preparation and was not bound to the kerogen. The alternative explanation is that the diterpenoids are released at an early stage of diagenesis and, hence, occur only in the bitumen. 5

Biomarker distribution in the pyrolysates of Australian Gippsland Eocene Coal kerogen

2! E

A predominance of CZ9LYLY(Y 20R sterane (Fig. 4) and the absence of CZ7steranes are noted in the distribution of steranes from the pyrolysates of 2- 10 h heated GEC kerogen. This distribution is suggestive of higher plant input with little or no marine plankton contribution. However, significant amounts of Cz8 (YLY(Y 20R and Cz7 a&9 20( R + S) are present in all the pyrolysates.

Is 2050

2100

2160

2200

22w

2300

2350

2400

GIPPSLAND COAL

CRETACEDUS KEROGEN

2450

Scan Number FIG. 5. Mass fragmentograms of triterpanes (m/z 19 1) obtained from the natural bitumen and pyrolysates of GEC kerogen ( 300°C).

Biomarker Distribution of the Pyrolysates of Humic Coal Kerogens at 300°C The distribution of biomarkers in the pyrolysates of Rocky Mountain Coal kerogen The distribution of steranes in the pyrolysates generated from RMC kerogen ( LU et al., 1989) is similar to that in the bitumen. Two significant differences between the original bitumen and pyrolysates are ( 1) the presence of C29 CI(Y~! 20s steranes in the pyrolysates but not in the bitumen and (2) the appearance of CZ7 (YQ(Y 20R steranes in the pyrolysates of coal kerogen heated to 1000 h (but not in kerogen pyrolyzed for only 2 to 100 h). The hopane distribution obtained from the 3OO”C, 2 h pyrolysate shows that the /3/3hopanes of carbon numbers 27 and 29-32 are dominant (Fig. 1). With progressive heating, the cu/3hopanes become major components in the pyrolysates and dominate over the immature &I and /3a!hopanes, which eventually disappear in the sample heated to 1000 hrs. The ratios Cj2 qY-22S/S + R and Csl &22S/S + R, which have earlier been proposed as maturation indices (MACKENZIEet al., 1980), increase consistently with heating time in the current study (Fig. 10; Table 1). The ratio 1~CXto 17/3-C2, trisnorhopane (Fig. 11; Table 1), considered as

1900

1950

2oGa

2050

21w

2150

2200

2250

2300

Scan Number

F1~.6.Massf?agrnentogramsofsteranes(m/z217)obtainedfrom natural bitumen of GCC and pyrolysates of coal kerogen at 300°C.

S.-T. Lu and 1. R. Kaplan

2768

GIPPSLAND

CRETACEOLJS

COAL

the amount of hopanes remaining is only about 10% of that produced from 100 h pyrolysis. In parallel with the presence of Cz9 (YLYOI 2OS/S + R sterane, the maturation level based on the ratios of C3, and C3* aP 22S/S + R hopane, increases with heating time from 2 h to 1000 h (Fig. 10). Furthermore, the ratio of Cz7 17a to 17p hopane increases very rapidly in the pyrolysates of the GEC kerogen with progressive heating (Fig. 11; Table 1). As was also observed in the pyrolysates of RMC, the diterpanes are absent in all pyrolysates of GEC.

KEROGEN

Biomarker distribution in the pyrolysates of the Australian Gippsland Cretaceous Coal kerogen 5 d

The distribution of steranes in pyrolysates generated from the GCC kerogen is also dominated by Cz9 CX(YCX and Cz9 pacu steranes (cam 20R, (Y(YCX 2OS, BLY(Y 20R, and @a 20s; Fig. 6). Significant amounts of C28 and C2, steranes were also determined to be present in the pyrolysates by retention time in the m/z 2 17 mass fragmentogram. In addition, some rearranged steranes are observed in the pyrolysates, but fewer than are found in the original bitumen. In contrast to GEC, the Cz7 (YLYCX steranes are present in

E

WILCOX

,,I,,,

2050

2100

II,,

2150

III!

2200

III1

2250

OII

2300

,I,,

II!1

2350

LIGNITI

2400

2450

Scan Number

FIG. 7. Mass fragmentograms of triterpanes (m/z 19 I ) obtained from natural bitumen of GCC and pyrolysates of coal kerogen at 300°C.

With continued heating to 1000 h, the ratios of Cz9 (Y(Y(Y 2OS/S+ RandC29~/3/3(S + R)/&(S + R)+ c~cucu2O(S + R) (Fig. 12) increase in this coal, reaching maximum values of 0.55 and 0.61 for C29 (II(Y(Y 2OS/S + R and Cz9 &B/a/3/3 + (YCNY, respectively (Table 1). They correspond to extracts of rock which are in the oil generation stage of catagenesis. In contrast to the original bitumen, the pyrolysates only contain a small amount of Csl (~/3 22R hopane relative to Cz9 and Cso a/3 hopanes (Fig. 5 ) , (cf. the original bitumen and pyrolysates of the RMC kerogen). As previously discussed ( LU et al., 1989)) the C3, (Y@22R hopane is released during early stages of diagenesis. On the other hand, Cz9 and CXo a@ hopanes dominate in all pyrolysates. The Cz9, C30 and C3, moretanes decrease with heating time. Thus, Cz9 and Cu, hopanes are the most resistant homologs generated during kerogen pyrolysis at 300°C. In addition, the total yield of hopanes obtained from pyrolysis increases with heating time from 2 to 100 h, indicating that the generation of hopanes is also important in addition to isomerization at this stage of maturation. Degradation becomes dominant in the samples heated longer than 100 h. For example, after 1000 h heating,

1900

1950

2m

2050

2100

2150

2200

2250

2300

Scan Number FIG. 8. Mass fragmentograms of sterane (m/z 2 17) obtained from natural bitumen and pyrolysates of kerogen from Wilcox lignite.

2169

Aromatic hydrocarbons in different coals

Km@Cl

WILCOX LlGNlTf ,. KEROGEN 11 Original Extract

16

I+2

L..L Fymiyz.xd:

7

3

;

5

~wntain Cod

-0

~oeky

-.-0

Qip~fmd

---e

Wilcox Lignite Kno~sn

Karogm

Eocma Coal Ksrogen

WC

2 lw”rr

11

2

-

I

I

I

I

I

I

I

2

4

6

8

10

12

14

c27 17a I1 78

trfsnorfmpane

Foci. 11. Ratios of C2, 174 170 trisnorhopane obtained from pyrolysis of various humic coals ( 300°C).

2460

2450

Scan Number

FIG. 9. Mass fragmentograms of triterpanes (m/z 191) obtained from natural bitumen and pyrolysates of kerogen from Wilcox lignite.

the series of pyrolysates (2-1000 h), reflecting that a possible marine or lacustrine algal input might be more significant in GCC than in the GEC. It is also possible that, due to its higher maturity, the secondary Crr steranes present in the

pyrolysate of GCC started to form during diagenesis or early catagenesis. The ratios of Cr9 (Y(Y(Y 2OS/ S + R sterane in the pyrolysates are about 0.43-0.49, which is close to 0.48 found in the original bitumen. The ratio is lower (0.43) in the pyrolysates of short term heating (2- 10 h) than that in the original bitumen. If the bitumen is indigenous, the lower values in the pyrolysates may reflect a faster isomerization rate having occurred in the natural bitumen (in situ) than in the kerogen. However, an alternative interpretation may be that some of the bitumen had migrated from a deeper formation. Nevertheless, there is still an increasing trend of Cr9 (Y(YLY 2OS/S + R with heating (Fig. 12 ) for the pyrolysates. The hopane distribution in the pyrolysates is dominated

Pyrofysis = 300’ C

---*

Wilcox Lignite

-..+.

Gippsland Cretacaou~ C-1

-.-0

Gippland Eocene Coal

‘P ’

\.\.:i.. \\ ai

I

E ._ c

,

I

0.2

b

1 0.4

17~. 228 + 22R

a

I 0.6

21j9-C31

1

1 0.8

I

a

hopnar

0.2 &&17a.

I

r’

P: !:

’

4

i

I

0.4

I

Wilcox Lignite

. . . . ..b

Gippcfmd Cretabour Coal

-e--O

Gippslmd Eoa

Coal

10

._

1.:

‘\”\

Rocky Mountain Coal

---*

2

f :

\

f.W+: -0

100

:

1000

I

0.6 218x32

I

I

I

1

I

b

I

I

0.8 hopam

FIG. 10. Ratios of 22S/22S + 22R 17~1218C1, and G2 hopanes obtained from pyrolysis of various humic coals (3OO’C).

0.2

0.6

0.4 20s -QP(I 20s + 20R

cm

0.8

staranas

FIG. 12. Ratios of 20s / 20s + 20R ~a Cz9steranes obtained from pyrolysis of various humic coals (3OOT).

S.-T. Lu and 1. R. Kaplan

2770

by (Y@hopanes from C2, to C3s (Fig. 7). A pronounced difference between the original bitumen and the pyrolysates is that CsI ~$322( R + S) hopanes predominate in the bitumen, whereas CZ9,C&, in addition to C,, o/3 hopanes, are all abundant in the pyrolysates. Furthermore, the maturation index of hopanes, i.e., (~/322S/S + R of Csl and CX2,increase with time of heating. The ratios range from 0.51 to 0.59 for Cf, and from 0.48 to 0.58 for CX2, respectively, for 2-1000 h heating (Fig. IO), whereas they are 0.58 and 0.59, respectively, in the original extract. Again, the ratios are slightly higher for the original bitumen than those in the pyrolysates of short term heating (2-10 h), as a result of a higher isomerization rate in the in situ bitumen than in the pyrolyzed kerogen, or as the result of bitumen components having migrated upward from a deeper formation. It appears that C& a@ and other secondary hopanes, such as C2, and CZ9o/3 hopanes, are the most resistant to degradation under pyrolysis, as their relative amounts increase with heating time. On the other hand, the extended ( rC3, ) hopanes are more susceptible to degradation due to the cracking of the side chain. Previous results reported by SEIFERTand MOL~WAN ( 1978) suggest that the ratio of the secondary (CZ7 + CZs) terpanes to primary (CB + C,) can be used as a maturation parameter. Biomarker distribution in the pyrolysates of Wilcox Lignite kerogen The steranes are dominated by CZgCYBCX and @cvcv 20R isomers as a result of higher plant input (Fig. 8 ). There is no CZ7ola?cr20R sterane present in the pyrolysates of 2- 1000 h (Fig. 8). However, CZ8sterane begins to appear in the 10 h pyrolysate, and the Cr9 CYCNY 2OS/S + R increases with maturity. The biological hopanes are still dominant in the short term pyrolysates (2- 10 h), and J3cumoretane becomes dominant in the 100 h pyrolysates. The stable geologic hopanes (43) become relatively more significant in the 1000 h pyrolysates (Fig. 9). The maturation indices, such as Cj, and CX2cup 22 SIS + R and CZ, t7o/ 178, increase with heating time. The ranges of these ratios are very close (0.10-0.54 and 0.13-0.56 ) for C3, and CsZcup,respectively, indicating that they follow similar isomerization rates upon thermal stress. Again the C27 17a:/ 17@hopane ratio is very sensitive to thermal stress (Fig. 11) and increases from 0. I to 11.25. The pyrolysates of WL only contain C3,, CQ, and C33 extended hopanes, whereas the pyrolysates of the two Gippsland coals are composed of C3,-& extended hopanes. This may reveal differences in the contributing plant species, although higher plant terrigenous inputs are considered to be dominant in all four coals studied. Comparison of Biomarkers Among Coals Studied

The Cz9 sterane is the dominant bitumen extracts and pyrolysates This is consistent with results of from Indonesia Kalimantan coal.

component in the natural of the four coals studied. HOFFMANNet al. ( 1984) C2, sterane is only present

in the series of pyrolysates (2- 1000 h) of GCC, and the pyrolysates from long term ( 1OO-IO00 h ) heating of RMC and GEC. The presence of CZ7sterane in pyrolysates may indicate the presence of marine or lacustrine algal (planktonic) input which was trapped in the kerogen and released after heating. It is also possible that the CZ7sterane in pyrolysates may also be derived secondarily from the cracking of Cz9 or CZ8steranes. Furthermore, CZs sterane is relatively more abundant in the pyrolysates of Australian coals and Wilcox lignite than in the RMC. Swamp environments were probably present during the deposition of Australian Gippsland coals, similar to the depositional history of WL ( MATHEW et al., 1981). The content of steranes is relatively low in the natural bitumen from the very immature coals of GEC and WL, suggesting that sterols may not yet have been converted to steranes. The ml z 191 mass f~~ent~s of the natural bitumen extracts of various humic coals are consistently dominated by Cj, cup 22R hopanes, whereas C3, 01822R hopane is only present in small amounts in the pyrolysates of all four coals. The only exception is the bitumen extract of GCC, in which C3, (~j322s is greater than Cji CUB 22R. This may be explained by its greater maturity than that of the other coals. In the extract of WL, triterpenes are also present in significant amounts in addition to Cj, o/3 22R hopane. In general, the distribution of hopanes in various humic coals is maturationand source-dependent. It is interesting to note that the C,i and C32 hopane maturation indices are different for the short term pyrolysis (210 h) of the two Australian Gippsland coals, but approach a steady state (equilibrium) in the long term ( 100-1000 h) pyrolysis (Fig. 10). However, both ratios from the pyrolysates of RMC and WL increase through the entire pyrolysis period

0.2 1

I-

+

0.1

0.2

I 0.3

~ 20s 0a(2 Cm mranea, 20s + 26R

0.4

/ 0.5

-cr/322s 22s + 22R

0.6 C3,

/ 0.7 or C32 hopanes

FIG. 13. Correlation between the ratios of 2OS/2OS+ 20R (Y(YOL C,, steranes and 22S/22S + 22R cx@ C,, and C,, hopanes and vitrinite reflectance for RMC and GEC kerogens (300°C).

2711

Aromatic hydrocarbons in different coals 2255

Australian

Gippsland

Cretaceous

coal

I + petylene

i

2158

2359 1 Australian

;

-

Gippsland

Eocene coal

2266

Rocky Mountain

coal

j 2235

’

I

I+ perylene

2157

1913

Wilcox

22

j

2277

lignite

229 I+

2160

2260

24&

Scan Number FIG. 14. Mass fragmentograms of monoaromatic steroid hydrocarbon (m/z 253) obtained for the natural bitumen of the four coals studied.

(2-1000 h). In addition, Fig. 12 also shows that the ratio of Cz9 aaa 2OS/S + R sterane differs in RMC and WL from GEC and GCC. This may suggest that these maturation indices in exinite-poor coal may take longer to reach equilibrium and hence may not follow the model of MACKENZIE ( 1984), which hypothesizes that these indices are only good in the range of & up to about 0.9%. The vitrinite reIIectance of residual coal kerogen of RMC after 1000 h pyrolysis is 1.2% & (Table 1). Surprisingly, the distribution of triterpanes and steranes in the pyrolysates of RMC kerogen conform more to immature products than do those of GEC kerogen. All maturation indices of biomarkers are lower for RMC than those from GEC (Fig. 13), although the vitrinite reflectance (&) of the starting and residual coal kerogens is consistently higher in the RMC than in the GEC. This may result from the GEC containing a significant amount of protistids and bacteria which may result in reducing the measured vitrinite reflectance (G. TAYLOR, per-s. commun. 1988). Moreover, it is

also possible that vitrinite reflectance and biomarker isomerization processes follow different kinetics. Nevertheless, the maturation indices, e.g., C29 aaa 2OS/S + R and Cs, or Cj2 afl 22S/S + R, increase (although at different rates) with maturity and heating time during pyrolysis for both RMC and GEC kerogens. In contrast, it seems that these biomarker maturation indices correlate well with thermal alteration in GCC (Rr, = 0.52%) and WL (& = 0.32%). WL, the least mature of the coals studied, has correspondingly lower maturation indices, whereas GCC has the highest ratios. The biomarker maturation, therefore, varies with both the coal composition and/or burial depth (temperature) within a basin. The significantly different composition of diterpanes between RMC and GEC may elucidate the difference in species of higher plants input. Only tricyclic diterpanes are present in RMC natural bitumen, whereas tetracyclic and tricyclic diterpanes are present in GEC bitumen. For lack of additional data, currently we speculate that the difference in diterpane distribution may be due to the diterpenoid components of

2772

S.-T. Lu and I. R. Kaplan Relative

Amount

Relative

205 DIA C27 MAS 20R 58 C27 MAS 20s 5a C27 MAS

0 n

I

P

a

Amount

0 % u 9

-0

,

P 0

20s 58 C28 MAS _

0-

P

6

20R 5u C27 MAS _ 20s 5a C28 MAS -

62 g i m

8 m 0 xl m 2 0 :: 5

2

20R5SC28MAS

_

g5 m

20s 5s c29 MAS 20s 5a c29 MAS

z

-

20R 5a C28 MAS 20R 5s C29 MA.9 20R 5a C29 MAS

2OS5SC27MAS

:

’

’

’

:

’

’

’

20s DIA C27 MAS ,

’ ;D

20R 5s C27 MAS 20s 5a C27 MAS 20s 5 S C28 MAS 20R 5a C27 MAS 20s 5 a C28 MAS

--I

20R 5s C28 MAS

Bi O-

20s 58 c29 MAS

:: ,--

20s 5a c29 MA.9

‘5 Z

-1

20R 5~ C28 MAS

m

20R 56 C29 MAS 20R 5a C29 MAS FIG. 15. Monoaromatic steroid hydrocarbon historgram distribution for the four coals studied. the resins of the conifers in the two hemispheres. For example, the present-day forests in the northern hemisphere are comprised mainly of species in families Pinaceae, Capressaceae, and Taxodiaceae, whereas those in the southern hemisphere are dominated by species in the families Araucariaceae and Podocarpaceae (WESTON et al., 1989 ) . Furthermore, the low content or absence of diterpanes in WL may result from a lack of resin input during deposition of the coal. Aromatic Hydrocarbons Aromatic steroid hydrocarbons in natural bitumen The distribution of monoaromatic steroid hydrocarbons (MA steroids) from the natural bitumens of four coals studied

are dominated by Cr9 MA steroids, especially 20R of both 5a and 50 Cz9 MA-steroids. C2, MA-steroids are only present in trace amounts or are absent in the bitumen (Fig. 14, Table 5 ) . The distribution of Cr, , Czs , and Cz9 MA steroids of the natural bitumens of the coals have been plotted in histograms and on a ternary diagram (Figs. 15 and 16). All four coal have a Cz7/G7 + C2s + CB and Czs / Cr, + Cz8 + CB of MAsteroid ratios less than 0.03 and 0.24, respectively. These results illustrate that both the distribution of steranes and MA steroids are dominated by Cz9, supporting the interpretations of HUANG and MEINSCHEIN( 1979), who suggested that terrigenous material derived from higher plants, have primarily Cr9 sterols. Thus, the results indicate that for these coals, the

2113

Aromatic hydrocarbons in different coals Table 5: Monoammatic steroid hydrocarbon

a

2os,$3 C27-Monoaromatic

steranc

C27H42

b

2OS,dia C27-Monoaromatic

steranc

C27&2

c

24)R,5$3C27Monoaromatic

sterane + 2OR C27 dia MAS

d

2OQa

steranc

C27H42

e

20&S@ C2g-Monoaromatic

sterane + 24X CD dia MAS

C2#44

f

20R,Sa C27-Monoaromatic

sterane

C27H42

g

2oS,sO CB-Monoaromatic

sterane

C28H44

h

2OR,$3 Cz-Monoaromatic

sterane + 2OR CB dia MAS

C28H44

i

2OS,S/3 C2g-Monoaromatic

sterane + 24B C29 dii MAS

C29H46

j

2OS,5a C2gMonoammatic

sterane

C29H46

k

2OR,5a CmMonoaromatic

sterane

C28H44

1

2OR,Sp C2pMonoaromatic

sterane + 2OR C29 dia MAS

C29H46

m

20R,5a C29-Monoaromatic

sterane

C29H46

C27-Monoaromatic

input of sterol precursors is almost entirely derived from higher plants. HOFFMANN et al. (1984) reported a similar distribution with a predominance of Cz9 steranes and Cz9 MA-steroids in oils from the Mahakam Delta, Indonesia. The immature coals, GEC, RMC, and WL, have a similar distribution of MA steroids, which is quite different from that of GCC, the most mature coal in this study. The significant difference is that GCC has low amounts of Sa C29 MA steroid due to its higher maturity, whereas it is the most abundant in GEC, RMC, and WL. However, the m/z 253 fragmentograms demonstrate that Sa! 20R Cz9 MA content decreases when S/3 20R Cz9 MA-steroidal content increases. Similarly, 5cr 20s Cz9 MA content decreases when 5/l 20s Cz9 MA-steroidal content increases. The level of maturity is very important for the type of aromatization of aromatic steroidal hydrocarbons in these

C27

80

identification.

100% c29

FIG. 16. Monoaromatic steroid hydrocarbon distribution; composite for the four coals studied.

four coals. Triaromatic steroid hydrocarbons (TA steroids) are only present in the natural bitumen of the most mature coal-GCC (Fig. 17, Table 6 ) . The distribution of m/z 23 1 is dominated by Cz,, components; similar to results reported in the oils and coal extracts from the Mahakam Delta, Indonesia ( HOFFMANN et al., 1984). MACKENZIE et al. ( 1980) suggested that the aromatization process occurs through the transformation from MA steroids by loss of one carbon atom. However, there is no C&& TA steroids in the original bitumens of the three immature coals (GEC, RMC, and WL). Nevertheless, a large amount of pentacyclic triaromatic and tetraaromatic components are present in the natural bitumen of the three immature coals (GEC, RMC, WL), appearing in the scanning range of TA steroids of m/z 23 1 (Fig. 18). Although the major peaks are tetra- and triaromatic pentacyclic, some unidentified components such as those peaks labeled as I, 2. 3, 4, 5, 6 with a prominent peak at m/z 145 or 158 and molecular ions at 344,376, and 378 (see Appendix) are also present. Similar spectra to these unidentified compounds have been found by FU et al. ( 1986) in coal extracts from Fushun coal mine, China. A number of triaromatic pentacyclic triterpenoid hydrocarbons are present in significant amounts in the natural bitumen of GEC, RMC, and WL (Figs. 19-2 1). Most of them have been previously reported from recent lake sediments (WAKEHAM et al., 1980) and from Australian brown coal (CHAFFEE and JOHNS, 1983). The compound labeled 8 in Figs. 18, 19,20, and 2 1 is the most abundant compound and has been identified as an oleanane-derived triaromatic hydrocarbon with a base peak of m/z 342 (WAKEHAM et al., 1980). Compounds 10 and 12 also contain the base peak of m/z 342, and they are probably different isomers of 8. Further, two additional peaks ( 7 and 9) with a base peak at m / z 257 and molecular ion at m/z 342 were also detected. WAKEHAM et al. ( 1980) also identified them as isomers of 8. Another series of peaks are labeled as II, 13 with a base peak at m/z 281 (molecular ion at 310, 324, respectively)

S.-T. Lu and I. R. Kaplan

2174

Natural

Bitumen

bbu

.-.-

100 Hrs.

1000 Hrs.

1608

2288

2888

1888

2488

2688

Scan Number FIG. 17. Mass fragmentograms of triaromatic steroid hydrocarbons (m/z 23 1) obtained from natural bitumen of GCC and pyrolysates of coal kerogen at 3OW’C.

Table 6:

Tl

Triaromatic

C~Triaromatic

T2 C2pTriaromatic

steroid hydrccarbon

identification.

sterane

C2oH20

sterane

C21H22

T3 20s C26_Triaromatic sterane T4 2OR Cz

+ 20s C27-Triaromatic

C26H32 steranes

C26H32 + C27H34

T5 ’20s C2gTriaromatic

sterane

Cm36

T6 MR C27-Triaromatic

sterane

C27H34

T7 2OR QpTriaromatic

steraoe

C28H36

2115

Aromatic hydrocarbons in different coals Table7: Theratioofm&wAimouclllte for thenaturalbltwwnsandpymlysates generated from humlccoal kcrogcnsat 3oo’C. R_MC

GEC

GCC

WL

0

1.65

0.47

1.25

0.25

pyrolysisHrs

2

2.66

3.42

2.08

1.66

10

4.70

28.86

2.81

1.69

100

17.71

Un

16.79

3.71

1000

Un

NP

Un

Un

Np: NotPresent.

Un: Ratioundctumlnable becameslmonellikhasdisappeared.

and peaks 14, 1.5 (Fig. 18) with a prominent peak at m/z 324 are present in the natural bitumen of GEC. They are also present in significant amounts in the natural bitumens of WL, RMC, and have been identified as tetraaromatic pentacyclic components (WAKEHAM et al., 1980). Specifically, compounds (II, 13, 14 and 15) were identified as 7-methyl3 ‘-ethyl- 1,2-cyclopentenochrysne, 1,2,9-trimethyl- 1,2,3,4tetrahydropicene, and 2,2,9-trimethyl-1,2,3,4_tetrahydropicene, respectively. Regarding the formation of the series of tetra- and triaromatic pentacyclic components, CHAEFEE and JOHNS ( 1983) proposed that they are possibly oleanane or ursane-derived

intermediates during progressive stages of aromatization, starting from &amyrinderived pentacyclic triter-penes. SPYCKERELLE et al. ( 1977) isolated a series of progressively aromatized hydrocarbon derivatives from the Eocene lacustrine Messel and Menat shales and Australian Miocene Yalloum lignite ( SPYCKERELLE et al., 1977). They proposed a reaction scheme by which tetracyclic chrysene derivatives and pentacyclic picene may be produced by dehydrogenation and aromatization of triterpene precursors. Of particular significance, is that these tetra and/or triaromatic components, labeled as 8, II. 12, 13. 14. and 15 in Fig. 18, have the oleanane skeletal structure. However, no

10&B145 _

I

I

I

I

.Jl

-.

I

._

_

16.4158 _

I

.

.A,.. . . . .__-- _,.__.

19.5. 191 _

65.9324

_

45.4342

_

Scan Number FIG. 18. Mass fmgmentograms of m/z 145, 158,231, the GEC.

342, 324, 191, and RIC obtained for the natural bitumen of

2776

S.-T. Lu and I. R. Kaplan

-I

T2

2

T2

Hrs.

$ % I5

t

100

T7

Hrs.

Scan Number Ro I 19. Mass fragmentograms of triaromatic steroid hydrocarbons (m/z 23 1) obtained from natural bitumen of WL and pyrolysates ofcoal kerogen at 300°C.

significant amount of ofeanane was detected in the ahphatic fraction. This indicates that the triterpenoid precursors prefer to form aromatic hydrocarbons throughout the dchydrogenation/aromatization instead of forming oleanane. It is interesting to note that the above tetra and triaromatic triterpenoids are present in the immature coals ( WL, GEC, RMC), whereas TA steroids are oniy present in the more mature coalCCC, which probably requires a higber temperature for generation. Supporting this suggestion are the spectra for the peaks which appear on the m/z 2 I 7 fragmentograms of the immature samples which do not correspond to steranes but rather to triterpanes fLv et al., I989; HOFFMAN et at., i984). This is different from that suggested by CHAFFEEand JOHNS( 1983 ). They proposed that the absence of aromatic steroids in the natural bitumen is because they

have preferentiahy

migrated during diagenesis, However, tetra and triaromatic pentacyclic compounds have been found in Recent lake sediments, indicating that these compounds can be formed at an early diagenesis stage, In addition, although it is interesting to note that there is no significant amounts OK&& TA steroids in the original bitumen of GEC, RMC, and WL, a peak can be identified in the mass spectrum of a C2, triaromatic steroidal hydrocarbon (Appendix) 1It appears in the three immature coals, but not in GCC. This would suggest that this Czl TA steroid was not derived from the side chain cracking of C&-c28 TA steroids, a~thou~ we also detected this compound in the pyrolysate of WL (Fig. 19) which has a simifar retention time and spectrum, indicating it is a C,, triaromatic sterane. WAKEHAM et al. ( 1980) also detected a compound with a

Aromatic hydrocarbons in different coats

2111

Natural Bitumen

FKG.20. Mass fmgmentograms of triaromatic steroid hydrocarbons {m/z 23 I ) obtained from natural bitumen of GEC and pyrolysates of coal keropn at 300°C.

simiiar spectrum in Recent lake sediment, where they identified it as 1-methyIi~p~pyI-7~8_nophenan~mue. Aromatic steroid hydrocarbons in the pyralysates of humic coal kerogens at 300dC In contrast to natural bitumen, no monoaromatic steranes were detected in the pyroIysates of four coals, probabIy because the destruction of monoa~matic steranes is more important than the aromatization at elevated temperatures, (i.e., 3OO’C) as Lu et al. ( 1989) proposed. In order to be sure that no monoaromatic steranes formed in the pyrolysates, both aliphatic and aromatic fractions were analyzed. Moreover, no significant peak has been detected with m f z 253 in either

fraction. Thus, caution should be taken in making interpretations on the natural occurrence of MA& because the temperature is criticaL in steroidai aromatization under thermal stress by pyrolysis. A significant amount of triaromatic sterane ( TA steroids) were detected in all the short term ( 2- 10 h ) pyrolysates (Figs. 17, 19, 20, 2 1) and were found to reach a maximum after IO h heating, decrease in the 100 h pyrolysates, and finally disappear in the pyraiysates of 1000 h heating. The distribution of m/z 23 1 in the pyrolysates is very similar to that in natural bitumen (GCC only ) , which is dominated by CB components. However, only a small amount af C2&& TA steroids was detected in the pyrofysate of WL (2- 1000 h ), whereas Gzt TA steroid is higher in WL pyrolysates than in

2118

S.-T. Lu and I. R. Kaplan

Natural Bitumen

2 Hrs.

I T5

100

T7

Hrs.

1000 Hrs.

2eb

22&J

Scan Number FIG. 21. Mass ~ento~arns of triaromatic steroid hydrocarbons ( M Jz 23 I ) obtained from natural bitumen of RMC and pyrofysates of coal kerogen at 300°C.

the pyrolysates of other coals. It is interesting to note that the generation of TA steroids does not neces%iIy derive f?om the aromati~tion of MA steroids, because there is no MA steroid remaining in the pyrolysates at& 2 h at 300°C heating. A significant amount of TA steroids form in the 10 h and even 100 h pyrolysate. Thus, TA steroids may be released directly from intermediate formed polar components such as asphaltenes and kerogen by partial breakup ofthe polymer networks upon thermal stress, as there is no evidence for its synthesis from MA steroids. Furthermore, it is interesting to note that there is no CzOor CZ, TA steroid formed in the pyrolysates of RMC, GCC, and GEC, although Cz, TA steroid was detected in the natural bitumen of GEC, WL, and RMC. Again, this provides evidence that it is not necessary to form CsOor C,, TA steroids via breakdown of side chains prior to

destruction of C&,4& TA steroids. As Figures 17, 20, and 2 I show, most of C&& TA steroids are directly destroyed by thermal stress, especially at ~rn~mtu~ as high as 3OO”C, without formation of Czo--C2,TA steroids. The formation of C&J,, TA steroids directly from kerogen or intermediate polar, asphaltene precursors should be investigated. Other types o~~iycyclic aromatic hydrocarbons Retene and simonellite. Retene ( i-me~yi-7-i~propyl phenanthrene) and simonellite are biological markers identified in sedimentary materials (SIMONEIT, 1977) and coal extract (WHITE and LEE, 1980). It is generally accepted that retene and simonellite are derived from abietic acid (SIMONEIT, 1977; LAFLAMMEand HITES, 1979), a common diter-

Aromatic hydrocarbons in different coals penoid acid in conifer resin and other high plant lipids (STONECIPHERand TURNER, 1970). Retene and simonellite were detected in the natural bitumen of four coals and especially are predominant in RMC which contains a sign&ant amount of resinderived diterpanes (Fig. 2). This further supports the suggestions that retene and simonelfite result from diagenetic aromatization of abietic acid. The relative abundance of retene is rich in the natural bitumen and the early pyrolysates (2-10 h) of RMC and GCC, but is much less abundant in the natural bitumen and pyrolysates of the two most immature coals (GEC and WL) . In fact, the relative abundance of retene and simonellite in aromatic fractions are in good agreement with the relative

2779

amounts of diterpanes in aliphatic fractions. The reason for the low amount of retene and simonellite in GEC and WL is unclear. This may result either from their low level of maturity or alternatively because the coals contain low amounts of resin. Both retene and simonellite are very dominant in the pyrolysates of short-term heating (2- 10 h), then decreased in 100 h pyrolysates. In the 1000 h heating experiment, simonellite is no longer present in all coal-kerogen pyrolysates, whereas retene still remains in all but GEC pyrolysate. However, the relative amount of retene is greater than simonellite in the natural bitumen of RMC and GCC, whereas simonellite is higher than retene in the natural bitumens of GEC and

1

Natural Bitumen

t”‘~r”“r““,“‘~l”.‘,“~~,~~~~,~~.~~ 2600

2700

2600

2900

3000

Scan Number Fto .22. Mass fmgmentograms of benzohopanes (m/z 191) obtained from natural bitumen of RMC and pyrolysates of coal kerogen at 300°C.

S.-T. Lu and I. R. Kaplan

2780

found benzohopanes in the reduced vitrinite from the Fushun coal mine. Furthermore, HE and Lu ( 1990) proposed a maturity parameter based on monoaromatic hopanoids by using the relative abundance of two monoaromatic hopanoid groups-the ring D aromatized 8,14+ecohopanoids and the benzohopanes. In addition, they concluded that the monoaromatic hopanoids are especially present in coal macerals that have oil-potential, from hopanoid precursors in a petroleum producing environment. In this paper, we focus on how widespread these compounds are among the different coals and their relative distribution during pyrolysis. The benzohopanes (Czz-C& ) are present in high concentration in natural bitumen (Fii. 22,23) of GCC, GEC, RMC, but in lower abundance in WL. This su8ger& that a microbial

WL (Table 7), but the retene to simonellite ratio increases constantly in the pyrolysates with heating. This may indicate that the formation of retene results from aromatization of simonellite. Furthermore, according to the relative abundance of retene and simonellite in the natural bitumens and pyrolysates, it appears that they can form by two pathways; the first is release during the early stages of d&genesis directly from higher plant resin, as previously reported by SNOWD~N ( 1980), and/or second, they can be formed by release from kerogen during early stages of catagenesis. Benzohopanes. A series of benzohopanes (C&Z35) were first identified in carbonate source rocks (HUSSLER et al., 1984) . Later, the benzohopanes were detected in extracts of Lower Jurassic black mudstone in the coal-bearing strata from the Junggar Easin (SHENG@ al., 1985). Fu et al. ( 1986) also

27fl ~d~ral

Biturn-

2855

2800 Seen

FIG,

Number 23. Mass fragmentograms of henzohopanes (m/z 19I ) obtained from natural bitumen of GCC and pyrolysates

of coal kerogen at 300°C.

Aromatic hydrocarbons in different coals

natural bitumen of CCC, whereas Cjq and Css are highest in GEC. RMC contains abundant amounts of CSZ, but a very small amount of CSS.A relatively low amount of benzohopane is present in the natural bitumen of WL, which is enriched in CS2and C33. For the relative distribution of benzohopanes, it seems that the side chain starts to crack and form smaller molecular sizes of benzohopanes under thermal stress. Consequently, CJI and CS2 are the most abundant in the pyrolysates of all four coals. Nevertheless, the relative distribution of benzohopanes present in the natural bitumen may vary with their original hopanoid precursors. Peryiene, benzopyrene, and benzojluoranthene. Perylene has been found in bituminous coal extracts ( WHITE and LEE, 1980)) in peat ( AIZENSHTAT, 197 3 ) , and in sediments ( ORR

hopane precursor, such as bacteriohopane tetro13 might be a significant component in coal ( HUSSLERet al., 1984). Furthermore, as GEC, RMC are immature and the GCC is at an early maturity level, the benzohopanes must be formed at a relatively early stage of diagenesis. The benzohopanes are consistently present in the pyrolysates of all four coals, but disappear or are present in trace amounts after 100 h heating at 300°C pyrolysis. This indicates that the structure of benzohopanes are unstable and degrade under advanced thermal stress. Furthermore, the carbon range of benzohopanes in the pyrolysate are slightly different from that in natural bitumen (Figs. 22,23 ) . Various relative amounts of Cs+.& benzohopanes are present in the pyrolysates of the four coals. C32 and CS4 are relatively high in

2125

1 1023 ___d_

1

187ti .___-

-.

Natural

Bitumen

1339 __----

-.

2 Hrs.

h

100Hrs.

1

1000Hrs.

18b3

V

2141

‘1

2781

1*

2188

2& Scan

Number

FIG. 24. Mass fragmentograms of m/z 252 obtained from natural bitumen of CCC and pyrolysates of coal kerogen at 3OO’C.

S.-T. Lu and I. R. Kaplan

2782

and GRADY, 1967; VEN~ATESAN,

1988). It was suggested by AIZENSHTAT ( 1973) that its precursors arise predominantly from land plants which are deposited with detrital minerals. With geologic time, the biogenic pigment precursors of perylene are converted to the polycyclic aromatic hydrocarbons. A significant amount of perylene (V) was detected in the natural bitumen of four coals (Figs. 24,25) and most of their pyroiysates (2- 1000h ) , but the abundance of perylene decmased with heating time (Figs. 24,25). On the other hand, other polycyclic aromatic hydrocarbons with five rings and with a base peak at m/z 252, such as henzo(b + k)Iluoranthene (peak I), benzo(e)pyrene (peak III) and ~nzo(a)p~ene (peak IV} are absent or in small amounts in the natural bitumen but increase with thermal alteration. An additional measured peak, labeled as ZZ(Figs. 24, 25 ),

has never been reported in the coal extracts. We tentatively

identified it as benzo(a)fluoranthene, based on its elution alter benzo(b f k)fluoranthene but prior to benzo(e)petylene (WISE et al., 1986). This peak also increases with thermal stress. Finally, benzofluoranthenes and benzopyrenes became the major aromatic components for the fang-term pyrolysates ( 100-1000 h). In fact, we have observed that a large amount of perylene is present in immature oils (e.g., Monterey oil) and source rocks (unpubl. data), whereas only benzo( b + k)fluoranthene and benzo( e)pyrene are detected in very mature oils (unpubl. data). This is in good agreement with the disappearance of perylene and other tetra- and triaromatic triterpenoids in long term pyrolysates. Thus, we suggest that a ratio of benzo(e)pyrene/perylene should be a good maturity parameter (Figs. 24, 25 ).

Z

1 __

Nabrat

Bitumen

i/

1867

---

fXi

2823

Kg?0

. __ __a_----

-

__L.__.__ -

21.56.22$!6

.

t -

‘----- -t

2136 2 Hrs.

2114

I

2qB ,2844

I

2i63

2221

I

f

“f

2:38

10 Hrs.

Scan

Number

FIG. 25. Mass fragmentograms of m/z 252 obtained from natural bitumen of RMC and pyrolysates of coal kerogen at 300°C.

Aromatic hydrocarbons in different coals CONCLUSION 1) The presence of high relative amounts of Cz9 sterolde-

rived species in all of the coal natural bitumens is characteristic of land-plant derived organic matter and is consistent with earlier results from other investigators. Furthermore, GEC and WL contain higher abundance ofCz8 sterane than other coals, suggesting that both coals formed in similar swamp environments. 2 ) The tricyclic diterpanes are the only diterpanes present in RMC, whereas tetracyclic and tricyclic diterpanes are both present in GEC and GCC, and WL contains no diterpanes. The different composition of diterpanes might result from differences in the diterpenoid components of the resins of the conifers in the two hemispheres, or absence of conifers in the WL de~sition~ en~ronment. 3) Diterpanoid hydrocarbons are very abundant in the original bitumen, but only present in trace quantities in the pyrolysates. This suggests that resinite, the most likely precursor of diterpenoids, was not bound to kerogen. Alternatively the diterpenoids are released at an early stage of diagenesis and enter the bitumen fraction. 1 The distributions of m / z 2 17 peaks in the bitumen from the two least mature coals are not typical of sterane distributions. This suggests that sterols are either absent in the starting material or have not yet converted to steranes (or sterenes) . The biomarker matumtion indices of 20 S/S + R C29 CY~LY sterane and 22SlS + R C3, or Cs2 ~$3hopanes increase with maturity (&) in natural bitumen and heating time in pyrolysates. However, these indices do not increase uniformly and vary significantly among the four different types of humic coals studied. 6) Signifi~nt amounts of mon~romatic steroids are present in the original bitumen of the four coals. The distribution of m/z 253 is similar in GEC, RMC, and WL, but differs from that in GCC due to its higher maturity. 7) Triaromatic steroid hydrocarbons are only present in the natural bitumen of CXC, whereas tetra and triaromatic triterpenoid hydrocarbons are present in the other three coals (GEC, RMC, and WL) and may be precursors to the polycyclic aromatic hydrocarbons or triaromatic steroids. A significant amount of triaromatic sterane was detected in all the short term pyrolysates reaching a maximum after 10 h heating, then decreasing and finally disappearing in the pyrolysates of IO00 h heating. 8) Retene and simonellite were detected in the natural bitumen of four coals, and their relative abundance in aromatic fractions correlate well with the relative amounts of diterpanes in aliphatic fractions. The retene/simonellite ratio increases with time of pyrolysis, but at 1000 h at 300°C all simonellite disappears and retene diminishes. 9) Renzohopanes are widely present in the four humic coals but become unstable during prolonged heating ( 100 h at 300°C). 10) The ratio of benzo( e)pyrene/perylene may be a potential maturity parameter because it is very responsive to heating time of kerogen.

2183

Acknowledgments-We would like to thank Global Geochemistry Corporation for allowing us to conduct the GC/MS analyses on aromatic fractions of bitumens and pyrolysates. We are grateful to Mr. E. Ruth for GCf MS ins~men~tion on aliphatic fractions and valu-

able discussion. Furthermore, the authors would like to thank Dr. M. I. Venkatesan, as well as Dr. Joseph Curiale and other GCA reviewers, for valuable discussion and review of the manuscript. We also want to thank Dr. M. R. Bhatia, Australian Aquitaine Petroleum Pty., Ltd., for providing the Gippsland coal samples and the late Dr. P. Given for providing the Rocky Mountain coal and Wilcox lignite samples. The vitrinite reflectance rn~u~rnen~ by C. C. Shen, C. L. Kuo, and T. H. Chou of Chinese Petroieum Corporation are deeply appreciated. Dr. H. Alimi assisted in constructing the ternary diagram of monoaromatic sterane carbon distribution. Finally, we appreciate the help of Rosario Pichay and Jean Sells for their typing and art work, respectively. This work was supported by NASA Grant

NGR-05-007-22I. Ed~tor~aihandling: S. A. Macko

REFERENCES AIZENSHTATZ. ( 1973) Perylene and its geochemical significance. Geochim. Cosmochim. Acta 3?,559-567. ALEXANDERA. P., VOROBIEVAN. S., and ZEMSKOVAZ. K. f 1985) Sterenes and triterpenes in brown coals. Or. Geochem. 8,269-

273. BARRICKR. C. and HEDGESJ. I. ( I98 1) Hydrocarbon geochemistry of the Puaet Sound reaion - II. Sedimentary diternenoid. steroid and triter$noid hydrocarbons. Geochim. ?osm&him. Acta 45, 381-392. BENDORAITIS J. G. ( 1973) Hydrocarbons of biogenic origin in petroleum~romati~ triterpenes and bicyclic sesquiterpene. In Advances in Organic Geochemistry (ed. B. TISZSOT and F. BIENNER), pp. 209-224. Editions Technip. CHAFFEEA, L. and JOHNSR. B. ( 1983) Polycyclic aromatic hydrocarbons in Australian coals. I. Angularly fused pentacyclic tri-tetraaromatic components of Victorian brown coal. Geochim. Cosmochim. Acta 47,2141-2155. Fu J., GUOYINGS., and DEHANL. ( 1986) Biomarker ~m~sition of certain Chinese oil-potential coal macerals (in Chinese). In Annual Research Reports of Organic Geochemistry Laboratory, Institute of Geochemistry, Academica Sinica (ed. SHI JIYANG et al.), pp. 32-49. Guizhou People’s Publishing House, Guiyang, China. GULYAEVAN. D., AREFIEVU. A., and PETROVAL. A. ( 1982) Pentacychc hydrocarbons Ct7-Ca in organic matter of coals of different catagenesis grades. Khimiya Averdogoto~ijva 1,30-35. HEW. and LU S. ( 1990) A new maturity parameter based on monoaromatic hopanoids. In Advances in Organic Geochemistry 1989 (ed. E. W. BAKERand A. G. DOUGLAS);Org. Geochem. 16,10071013. HOFFMANNC. F., MACKENZIEA. S., LEWISC. A., MAXWELLJ. R., OUDIN J. L., DURAND B., and VANDENBROUCKE M. ( 1984) A biomgical marker study of coals, shales and oils from the Mahakam delta, Kalimantan, Indonesia. Chem. Geoi. 42, l-23. HUANG W.-Y. and ME~NCHEINW. G. ( 1979) Sterols as ecological indicators. Geochim. Cosmochim. Acta 43,739-145. HUSSLERG., CONNANJ., and ALBRECHTP. ( 1984) Novel families of tetra- and hexacyclic aromatic hopanoids predominant in carbonate rocks and crude oils. Org. G&hem. 6,39-49. LAFLAMMER. E. and HITES R. A. ( 1979) Tetra- and pentacydic naturatty occurring aromatic hydr~r~ns in recent sediments. Geochim. ~osmoch~m. Acta 43, 1687- 169 i _ LEWANM. D.. BJOR@YM.. and DOLCATERD. L. ( 1986) Effects of thermal maturation on steroid hydrocarbons as determined by hydrous pyrolysis of phosphom Retort shale. Geochim. Cosmochim. Acta 50, 1977-1988. LIVSEYA., DOUGLASA. G., and CONNANJ. ( 1984) Diterpenoid hydrocarbons in sediments Born an offshore well. Org. Geochem. 6, 73-81. LU S.-T. f 1987) The role of minerals in the thermal alteration and

2784

S.-T. Lu and I. R. Kaplan

hydrocarbon generating potential of black shale and humic coals. Ph.D. thesis, University of California at Los Angeles. Lu S.-T., RUTH E., and KAPLAN I. R. ( 1989) Pyrolysis of kerogens in the absence and presence of montmorillonite-I. The generation, degradation and isomerization of steranes and triterpanes at 200 and 300°C. Org. Geochem. 14,491-499. Lu S.-T. and KAPLANI. R. ( 1990) Hydrocarbon generating potential of different humic coals estimated from dry pyrolysis. AAPG Bull. 14, 163-173. MACKENZIEA. S. ( 1984) Application of biological markers in petroleum geochemistry. In Advances in Petroleum Geochemistry (ed. J. BROOKSand D. WELTE), pp. 115-246. MACKENZIEA. S. and MCKENZIED. ( 1983) Isomerization and aromatization of hydrocarbons in sedimentary basins formed by extension. Geol. Msg. 120,417-528. MACKENZIEA. S., PATIENCER. L., MAXWELL,J. R., VANDENBROUCKEM., and DURANDB. ( 1980) Molecular parameters of maturation in the Toarcian shales, Paris Basin, France, I. Changes in the configuration of acyclic isoprenoid alkanes, steranes and triterpanes. Geochim. Cosmochim. Acta 44, 1709- 172 I. MACKENZIEA. S., BRASSELLS. C., EGLINTONG., and MAXWELL J. R. ( 1982) Chemical fossils: The geological fate ofsteroids. Science 217,49 I-504. MATHEWD., BAUERM. A., and TEWALTS. J. ( 198 I ) Near surface lignites of the Wilcox group in East-Central Texas. In GulfCoast Association of Geological Society Transaction 31st Annual Meeting

(abstr.). MOLDOWANJ. M. and FACO F. J. ( 1986) Structure and significance of a novel rearranged monoaromatic steroid hydrocarbons in petroleum. Geochim. Cosmochim. Acta 50, 343-35 I. MOLDOWANJ. M., SEIFERTW. K., and GALLEGOSE. J. ( 1985) The relationship between petroleum composition and the environment of deposition of petroleum source rocks. AAPG Bull. 69, 12551268. NOBLE R. A., ALEXANDERR., KAGI R. I., and KNOX J. (1985) Tetracyclic diterpenoid hydrocarbons in some Australian coals, sediments and crude oils. Geochim. Cosmochim. Acta 49,21412147. NOBLE R. A., ALEXANDERR., KAGI R. I., and KNOX J. (1986) Identification of some diterpenoid hydrocarbons in petroleum. Org. Geochem. 10, 825-829. ORR W. L. and GRADYJ. R. ( 1967) Perylene in basin sediments of Southern California. Geochim. Cosmochim. Acta 31. 120 1- 1209. PHILPR. P. ( 1985) Fossil Fuel Biomarkers: Applications and Spectra. F%ILPR. P. and GILBERTT. D. ( 1984) Characterization of petroleum source rocks and shales by pyrolysis - gas chromatography - mass spectrometry - multiple ion detection. Org. Geochem. 6,489-50 1. PHILP R. P., GILBERTT. D., and FRIEDRICHJ. ( 1981) Bicyclic sesquiterpenoids and diterpenoids in Australian crude oils. Geochim. Cosmochim. Acta 45, 1 I73- I 180. PHILP R. P., SIMONEITB. R. T., and GILBERTT. D. ( 1983) Diterpenoids in crude oils and coals of south eastern Australia. In Advances in Organic Geochemistry 1981 (ed. M. BJOR~Yet al.), pp. 698-704. J. Wiley. QUIRK M. M., WARDROPERA. M. K., WHEATLEYR. E., and MAXWELLJ. R. ( 1984) Extended hopanoids in peat environments. Chem. Geol. 42,25-43. RICHARDSON J. S. and MIILERD. E. ( 1982) Identification ofdicyclic and tricyclic hydrocarbons in the saturate fraction of a crude oil by gaschromatography/mass spectrometry. Anal. Chem. 54,7 IS768. ROHMERM., DASTILLUNG M., and OURISSONG. (1980) Hopanoids

from C30to Css in recent muds-Chemical markers for bacterial activity. Naturwissensch. 67,456-458. SEIFERTW. K. ( 1978) Steranes and terpanes in kerogen pyrolysis for correlation of oils and source. rocks. Geochim. Cosmochim. Acta 42, 473-484. SEIFERTW. K. and MOLDOWANJ. M. ( 1978) Applications of steranes, terpanes, and monoaromatics to the maturation, migration and source of crude oils. Geochim. Cosmochim. Acta 42,77-95. SEIFERTW. K. and MOLDOWANJ. M. ( 1980) The effect of thermal stress on source rock quality as measured by hopane stereochemistry. In Advances in Organic Geochemistry 1979 (ed. A. G. DOUGLASand J. R. MAXWELL),pp. 229-237. SEIFERTW. K. and MOLDOWANJ. M. (1986) Use of biological markers in petroleum exploration. In Biological Markers in the Sedimentary Rocks (ed. R. B. JOHNS); Geochem. Geophys. 24, 261-290. SHENGGUOYING, Fu JIAMO,ZHOU ZHONGYI,and SHENRULANG ( 1985 ) Benzohopanes-A novel family of biomarker compounds detected in Jurassic sedimentary rocks. Geochemica 1,75-79 (in Chinese with English abstr.). SIMONEITB. R. T. ( 1977) Diterpenoid compounds and other lipids in deepsea sediments and their geochemical significance. Geochim. Cosmochim. Acta 41,463-476. SNOWD~N L. R. ( 1980) Resinite-A potential petroleum source in the Upper Cretaceous/Tertiary of the Beaufort Mackenzie basin. In Facts and Principles of World Petroleum Occurrence: Canadian Society Petroleum Geologist Mem. 6 (ed. A. D. MIALL), pp. 421446. SNOWWN L. R. and POWELLT. G. ( 1982) Immature oil and condensate-Modification of hydrocarbon generation model for terrestrial organic matter. AAPG Bull. 66, 775-788. SPYCKERELLE C., GREINERA. C., ALBRECHTP., and OURISSONG. ( 1977) Aromatic hydrocarbons from geological sources. III. A tetmhydrochrysene derived from triterpenes in Recent and 01 sediments: 3,3,7-trimethyl- ,2,3,4_tetrahydrochrysene. J. Chem. Res. (M), 3146-3777; (S), 330-331. STONECIPHERW. D. and TURNER R. W. ( 1970) Rosin and rosin derivatives. Encycl. Polym. Sci. Technol. 12, 139- 161. THOMASB. R. ( 1970) Modem and fossil plant resins. In Phytochemical Phylogeny, Chap. 4 (ed. J. B. HARBORNE),pp. 59-79. Academic Press. VENKATESANM. I. ( 1988) Occurrence and possible sources of perylene in marine sediments. Mar. Chem. 25, l-27. VENKATESANM. I.. RUTH E.. and KAPLANI. R. (1986) Terpenoid hydrocarbons in Hula Peat: Structure and origins. Geochim. Cosmochim. Acta 50, 1I33- I 139. VOROBIEVAN. S., ZEMSKOVAZ. K., BODZEKD., KISELEVV., and PETROVAL. A. ( 1983) Hydrocarbons of the soluble part of bitumenous coal. Neftekhimiya 6, 755-166 (in Russian). WAKEHAMS. G., SCHAFF’NER C., and GIGER W. ( 1980) Polycyclic aromatic hydrocarbons in recent sediments-II. Compounds derived from biogenic precursors during diagenesis. Geochim. Cosmochim. Acta 44, 4 (5-429. WESTONR. J.. PHILP R. P.. and SHEPPARDC. M. ( 1989) Sesquiterpanes, dite&nes and other higher terpanes in oils from the Taranaki Basin of New Zealand. Org. Geochem. 14,405-42 1. WHITE C. M. and LEE M. L. ( 1980) Identification and significance of some aromatic compounds of coal. Geochim. Cosmochim. Acta 44, 1825-1832. WISE S. A., BENNERB. A., CHESLERS. N., HILPERTL. R., VOGT C. R., and MAY W. E. ( 1986) Characterization of the polycyclic aromatic hydrocarbons from two standard reference material air particulate samples. Anal. Chem. 58, 3067-3077.

Aromatic hydrocarbons in different coals Appendix

(e) Norpimarane lea.0

58.8

m/z

i

!

(gb) Fichtelite 188.8

se.0

m/z

(h) Isopimarane

58.0

m/z

(j)

Abietane

m/z FIG. A 1.Spectra of Norpimarane, Fichtelite, Isopimarane, and Abietane.

2185

2186

S.-T. Lu and I. R. Kaplan (ga)

e&-beyerane

(i)

166~ehyl

1m.e

.ocladane 97

7

123

50

m/z

(k)

2i0

1%

-ent-166-kaurane 1?3

100.0

IL 55

se.0

m/z

50

(1)

16wphyllocladane

lee.

e

1%

2ee

250

123

m/z

(m) -ent-lda-kaurane

m/r

FIG. A2. Spectra of ent-Beyerane,

16/3-Phyllocladane,

en&l 6&Kaurane,

16a-Phyllocladane,

and enf- 16aXaurane.

Aromatic hydrocarbons in different coals

VII. Abbmle

VIII. ~Kl”rme

FIG. A3. Molecular structures of Norpimarane, Clp-Tricyclicditerpane, ent-Ekyerane, Fichtelite, Isopimarane, Phyllocladane, Abietane, and ent-Kaurane.

TA steroid

56.0

Compound “1” 158

m3.a

Compound “3” 188.5 50.8

FIG.

A4. Spectra of C2, TA steroid, compound “1” and compound “3.”

2781

2788

S.-T. Lu and I. R. Kaplan Compound “4” 155

100.0 58.0

Compound “5”

50

100

150

100.0-

Compound “8”

:%?.a-

50.0-

M.‘Z 50

100

,163 ., I”“‘1 150

FIG. A5. Spectra of compound “4”, compound “S’, and compound “8.”