Energy & Fuels 1991,5,875-884
875
Comparative Geochemical Study of Three Maceral Groups from a High-Volatile Bituminous Coal P. Blanc,+J. Valisolalao, and P. Albrecht* Institut de Chimie, Universitg Louis Pasteur, 1 rue Blaise Pascal, 67008 Strasbourg, France
J. P. Kohut and J. F. Muller I.P.E.M.-TechnopGle, Universitg de Metz, 1 , boulevard Arago, 57070 Metz, France
J. M. Duchene Centre de Pyrolyse de Marignau, 57612 Forbach, France Received April 30, 1991. Revised Manuscript Received September 3, 1991 Three maceral concentrates (vitrinite, fusinite, and sporinite, over 90% pure) from the same high-volatile bituminous coal (Vouters, Lorraine Basin, France; 0.84% R,) have been analyzed for their organic solvent soluble (bitumen) and insoluble (macromolecularnetwork) fractions in the scope of a comparative geochemical study. Molecular marker distributions in the saturated and aromatic hydrocarbon fractions from the bitumen of vitrinite and fusinite were almost identical, whereas they were rather different for sporinite, probably due to a difference of origin. Hopanoid compounds were much more abundant in fusinite than in vitrinite, giving evidence for a major bacterial input in the former. The macromolecular networks have been oxidized with ruthenium tetroxide, a reagent known for its selectivity toward aromatic rings. Oxidation products reflect the high aliphatic character of sporinite (which yields essentially linear mono- and dicarboxylic acids) and the highly aromatic characters of vitrinite and fusinite (which yield essentially aromatic acids). Both oxidative degradation and Rock-Eva1 pyrolysis showed sporinite to be easily degradable and fusinite very resistant, at this level of maturity. Covalently bound hopanes are present in the matrix of sporinite; they appear less mature than the free hopanes in the bitumen, probably due to a protection of the macromolecular network. Hopanoids seem to have been incorporated in the matrix of fusinite. New coal rank parameters based on oxidation products of aromatic structural entities belonging to the macromolecular network have been proven to be more discriminating than rank parameters from the bitumen. They enabled the quantification of the level of condensation of the polyaromatic subunits of the macerals (fusinite > vitrinite > sporinite). Moreover, fusinite seems to behave like a 2% R, vitrinite-rich coal. These new parameters could find useful applications in the coking industry since they are able to differentiate between inert and reactive inertinites.
Introduction Since the name "maceral- was given to microscopically recognizable organic constituents of coals,' many petrographical investigations, but few chemical studies, have been done to characterize them. This was mainly due to the difficulty in isolating pure maceral fractions in sufficiently high amount to undergo geochemical investigations. Improvements in maceral separationH as well as in organic geochemical analytical techniques led to growing interest612 in their study. However, no systematic comparative molecular geochemical study of the three maceral groups from the same coal seam has been done yet on both their soluble and insoluble organic matter. This study reports the results of the investigation of the molecular and macromolecular structure of maceral concentrates from a high-volatile bituminous A French coal, belonging to three classical maceral groups vitrinite, inertinite, and liptinite, analyzed by means of solvent extraction, selective oxidation, thermodesorption, and Rock-Eva1 pyrolysis. Separation and analysis of the organic extracts of coals provide structural identification of molecular markers which can be used as rank indices.13 Previous studies showed that the widely used vitrinite reflectance parameter could fail in the case of vitrinite poor c0a1s.l~ Identifit Present address: Socidte Nationale Elf Aquitaine (Production), C.S.T.J.F., Avenue Larribau, L2-113bis, Pau, France.
0887-0624/91/2505-0875$02.50/0
cation of molecular markers in pure maceral fractions could be interesting in this respect, as well as provide useful information on the origin of their organic matter.l6J6 Investigation of the macromolecular matrix of coals or macerals requires selective methods. Previous oxidative degradations of kerogens or coals provided interesting However, the drawback of most of these (1)Stopes, M. C, Fuel 1935,14,4-13. (2)Totino, E.Ph.D. Thesis, UniversiG de Metz, 1986. (3)Totino, E.; Muller, J. F. C. R. Acad. Sci. Paris 1986,4,295-300. (4)Choi, C.,Dyrkacz, G. R.; Stock, L. M. Energy & Fuels 1987,I , 28C-286. (5)Allan, J.; Douglas, A. G. Ado. Org. Geochem. 1973 1974,203-206. (6)Allan,J.;Bjoroy, M.; Douglas, A. G. Adu. Org. Geochem. 1975 1977, 633-654. (7) Allan, J.; Larter, S. R. Ado. Org. Geochem. 1981 1983,534-545. (8)Davies, M. R.;Abbott, J. M.; Gaines, A. F. Fuel 1985, 64, 1362-1369. (9)Davies, M. R.;Abbott, J. M.; Cudby, M.; Gaines, A. F. Fuel 1988, 67,960-966. (10)Puttmann, W.; Wolf, M.; Wolff-Fischer, E. Org. Geochem. 1986, 10,625-632. (11)Hwang, R. J.; Teerman, S. C. Energy Fuels 1988,2, 170-175. (12) Landais, P.; Zaugg, P.; Monin, J. C., Kister, J.; Muller, J. F. Coal, Formation, Occurrence and Related Properties; Bulletin de la Soci€U Geologique de France: Paris, in press. (13)Blanc, P.; Albrecht, P. Aduanced Methodologies in Coal Characterization; Elsevier: New York, 1990;pp 53-82. (14)Corr6a da Silva, Z. C.; Ptittmann, W.; Wolf,M. 1987International Conference on Coal Science; Elsevier: New York, 1987;pp 165-168. (15)Brassell, S.C.; Eglinton, G., Maxwell, J. R. Biochem. SOC.Trans. 603rd Meet. 1983,11,575-586. (16)Ourisson, G.; Albrecht, P.; Rohmer, M. Sci. Am. 1984,251,44-51.
0 1991 American Chemical Society
876 Energy & Fuels, Vol. 5, No. 6,1991
Blanc et al.
Table I. Proximate, Elemental, and Petrographic Analyses of the Raw Vouters Coal" proximate analysis elemental analysis petrographic analysis moisture, % ash, % VM, % daf C, % H,% 0,% N,% S, % VR, %R, V, vol % L, vol % I, vol % MM, vol % 1.16 2.75 5.5 0.56 0.84 35.6 80.35 5.35 11.66 83.8 9.0 6.5 0.7
'VM
= volatile matter, VR = vitrinite reflectance, V = vitrinite, L = liptinite, I = inertinite, MM = mineral matter.
Table 11. Elemental Analysis of the sample C, % H, % 0, % N, % Vouters 80.35 5.35 11.66 1.16 coal vitrinite 79.47 4.93 12.13 0.98 fusinite 61.60 1.78 16.25 0.40 sporinite 79.66 6.46 7.80 0.89
Maceral Concentrateso S, % H/C at. O/C at. 0.56 0.793 0.109 0.83 1.92 1.04
0.739 0.344 0.966
1.6
-
,,.type
1.41.2
-
0.4
-
I
,,'
...-type
;
I1
0.115 0.198 0.074 I
,
"at. = atomic ratios.
degradations is their lack of ~ e l e c t i v i t y . ~The ~ use of ruthenium tetroxide (RuO,), well-known in organic chemistry for many years?, has become interesting in this respect since Carlsen et al.% found an improved procedure which was successfully applied for the investigation of coal s t r u c t ~ r e . l ~This * ~ reagent ~ seems to preferentially attack the aromatic entities of the coal network to liberate the aliphatic moieties as mono- or polycarboxylic acids. The efficiency of this oxidation reaction has been tested on several model ~ o m p o u n d s . ~ ~Identical - ~ ~ ' procedure was also applied to petroleum asphaltenes.29i30Recently, maceral fractions obtained by gradient density centrifugation were studied by this method:32 great differences were shown between liptinites, on the one hand, and inertinites and vitrinites on the other. In the present study, we have oxidized with RuO, under catalytic conditions maceral concentrates of the same coal obtained by hand picking. The results indicate that the chemical structure of the different macerals can be reflected in their oxidation products: special emphasis has been laid on the level of condensation in their macromolecular networks of the polyaromatic subunits, which can be quantified by means of new molecular parameters related to rank and type. Description of Samples The maceral separation was done on a high-volatile bituminous A coal, Vouters, located in the Lorraine Basin (France). Proximate, elemental, and petrographic analyses are given in Table I. This coal is vitrinite rich (84 ~ 0 1 % ) and its mean vitrinite reflectance value is 0.84% R,. Maceral concentrates have been obtained by direct hand-picking on preferential lithotypes. No gradient density centrifugation was done and the fractions thus obtained are rather pure (controlled under microscope): vitrinite concentrate is collinite 99% pure; inertinite is fusinite 99% pure; liptinite is a sporinite fraction 90% pure. The elemental analysis of the three macerals are given in Table 11, as well as their atomic H/C and O/C ratios which enable them to be plotted in a Van Krevelen diagram3"% represented on Figure l. Vitrinite concentrate is a typical type I11 organic matter from terrestrial origin,
I'
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.
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0
10
20
,
,
.
,
,
,
-----____ type 30
40
50
,
,
111
60
70
01(mg COVg TOC)
Figure 2. Position of Vouters coal and its macerals in a H I 4 1 diagram from Rock-Eval pyrolysis experiments (Fu = fusinite, S p = sporinite, Vi = vitrinite, Vo = Vouters coal). See Table I11 for details.
whereas sporinite, richer in hydrogen, behaves like a type I1 kerogen. The organic matter of fusinite seems to have been strongly reworked its relatively high oxygen content is in agreement with a strong aerobic degradation. The three maceral fractions as well as the raw Vouters coal have been characterized by Rock-Eva1 pyrolysis: typical parameters obtained from this method are given in Table 111. Interpretations will be given later on as a comparison with chemical study. However, the classical HI-01 diagram%confirms the results of elemental analysis (Figure 2). Some of the results from the macerals will be compared with results from a set of French vitrinite-rich coals covering a wide rank range (0.44-2.45% R0),13p38as well as two Australian inertinite-rich coals (0.97 and 1.18%R,; inertinite content around 40 V O ~ % ) . ~ ~ Experimental Section Extraction of Samples and Separation Scheme (Figure 3). Finely powdered maceral fractions (5g) were extracted with
Table 111. Parameters from the Rock-Eva1 Pyrolysis of the Vouters Coal and Its Macerals' HI, mg of HI, mg of T-, S1,mg of S2,mg of S3,mg of PC, TOC, HC/gof COz/gof maceral OC HCIe HCIn co./n PI S2/S3 % % TOC TOC sporinite 422 4.9 453.3 17.8 0.01 25.46 68.3 663 29 38.1 vitrinite 424 1.0 118.2 15.9 0.01 9.9 71.9 164 22 7.43 fusinite 440 0.9 29.3 10.3 0.03 2.84 2.5 62.6 46 16 Vouters coal 420 1.4 140.2 6.9 0.01 20.31 11.8 68.4 204 10 HC = hydrocarbons, PI = production index, PC = pyrolyzed carbon, TOC = total organic carbon, HI = hydrogen index, 01 = oxygen index. , I
,
I
.I
Y
Energy & Fuels, Vol. 5, No. 6,1991 877
S t u d y of Three Maceral Groups
7
Table IV. Extraction Yields of the Maoerals' maceral fusinite vitrinite sporinite % extract no. 1 0.5 1.8 1.7 % extract no. 2 0.3 1.8 1.3 % extract no. 3 0.2 1.8 0.3 % extract no. 4 0.1 1.6 0.2 % total extract 1.1 7.0 3.5
grinding
ground maceral concentrate
+
m r l h n wim m!uene/rneihanol 3 I
--ti--
I
a? '&
of maceral, see Experimental Section for details.
esterified organic extract
I
TLC SIO#Hexane
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-
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-
polar compounds
v n-alkanes
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i
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GC-US
1
"b) Furinlte h
polars
V
GC
I
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4
hopanes
GC-US
Figure 3. Analytical scheme used for study of the organic extracts of the macerals (see Experimental Section for details).
a mixture of toluene-methanol 3:l (v:v) (50 mL) in a beaker a t 50 OC overnight under vigorous stirring. T h e operation was repeated four times. T h e liquid phase was separated from the solid residue by centrifugation a t 4000 rpm and evaporated in a rotary evaporator t o yield total extract of maceral. T h e extraction residue was dried under vacuum and further used for ruthenium tetroxide oxidation (see below). Total extracts (bitumen) were esterified with diazomethane and then separated on thin layer chromatography (TLC, elution with n-hexane). Saturated and aromatic hydrocarbons were thus (17) Simoneit, B. R. T.; Burlingame, A. L. Adu. Org. Ceochem. 2973 -i974.i9i-2ni. - . -, - - - - - - . (18) Deno, N. C.; Jones, A. D.; Owen, D. 0.; Weinschenk, J. I. Fuel 1986,64, 1286-1290. (19) SteDhens, J. F.: Leow, H. M.; Gilbert, T. D.: Phib. R. P. Fuel 1985,64, 1531-1536. (20) Hayatsu, R.; Botto, R. E.; Scott, R. G.;McBeth, R. L.; Winans, R. E. Fuel 1986,65,821-826. (21) Barakat, A. 0.;Yen, T. F. Geochim. Cosmochim. Acta 1988,52, 359-363. (22) Vitorovic, D.; Ambles, A.; Bajc, S.; Cvetkovic, 0. Fuel 1988,67, 983-993. (23) Dumay, D.; Kirsch, G.;Gruber, R.; Cagniant, D. Fuel 1984,63, 1544-1546. 1953, 75,3838-3840. (24) Djerassi, C.; Engle, R. R. J. Am. Chem. SOC. (25) Carlsen, H. J.; Katauki, T.; Martin, V. S.; Sharpless, K. B. J.Org. Chem. 1981,46, 3936-3938. (26) Stock, L. M.; Tse, K. Fuel 1983,62,974-976. (27) Stock, L. M.;Wang, S. H. Fuel 1985,64, 1713-1717. (28) Stock, L. M.; Wang, S. H. Fuel 1986,65, 1552-1562. (29) W i i e f f , S. Ph.D. Thesis, Univeraite Louis Pasteur, Strasbourg, 1986.
(30)Trifilieff, S.; Sieskind, 0.;Albrecht, P. In Biological markers of sediments and petroleum; Moldowan, J. M., Albrecht, P., Philp, R. P., Eds.; Prentice Hall: Englewood Cliffs, NJ, in press. (31) Ilsley, W. H.; Zingaro, R. A,; Zoeller Jr., J. H. Fuel 1986, 65,
1216-1220. (32) Choi, C.; Wang, S. H.; Stock, L. M. Energy Fuels 1988,2,37-48. (33) Van Krevelen, D. W. Coal; Elsevier: New York, 1961. (34) Tiseot, B. P.; Welte, D. H. Petroleum Formation and Occurrence, 2nd ed.; Springer-Verlag: Berlin, 1984. (35) ESpitaliB, J.; Deroo, G.;Marquis, F. Reu. Inst. Franc. P6t. 1985, 40, 563-579,755-7&4, 1986,41, 73-89. (36) Blanc, P. Ph.D. Thesis, Universit6 Louis Pasteur, Strasbourg, 1989.
n
C)
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i
isoprenoids
v n-alkanes
o alkylcyclohexanes
i IbD
lb
.e
I ? '
ODD
ain
hopanes
. '
rm
1%
F i g u r e 4. Gas chromatograms of saturated hydrocarbons in (a) vitrinite, (b) fusinite, and (c) sporinite bitumen. Conditions: SE54, 40 m X 0.32 mm, 40-300 OC, 3 OC/min. obtained. T h e polar compounds were again separated on TLC by elution with dichloromethane t o obtain esterified acidic fractions. The various fractions were further analyzed by gas chromatography-mass spectrometry (GC-MS). Gas chromatographic studies were made on a Carlo Erba FRACTOVAP 4160 equipped with glass capillary columns and an on-column injector (SE 54, 30 m X 0.3 mm, 40-300 OC, 3 OC/min). Carrier gas was hydrogen at a pressure of 1kg/cm2. GC-MS studies were made on an LKB 9000 S with an ionization energy of 70 eV (injector temperature 290 "C; source temperature 250 OC; separation temperature 270 "(2). The GC-MS system was equipped with fused silica capillary columns (SE 30,25 m X 0.3 mm, 80-295 OC, 3 OC/min). Helium was used as carrier gas (1 kg/cm2). Ruthenium Tetroxide Oxidati~n.'~The solvent-preextracted macerals (500 mg) were suspended in a mixture of carbon tetrachloride (10 mL), acetonitrile (10mL), and water (20mL) and oxidized with ruthenium tetroxide formed in situ by the mixing of R u 0 2 (50 mg) and NaIOl (5 g), during 4 h. The mixture was then filtered on prewashed paper and the residue washed with
Blanc et al.
878 Energy & Fuels, Vol. 5,No. 6, 1991 a) Vltrinite
.
b) Fuslnite
.
* T"C
c) Sporinlte
-
T"C
-
T"C
Figure 5. Mass fragmentogramsm / z = 191 of the hopanes occurring in the bitumen of (a) vitrinite, (b) fusinite, and (c) sporinite concentrates. Chromatographic conditions: SE30, 25 m X 0.30 mm, 60-290 "C, 3 OC/min. Table V. SeDaration of the Organic Extracts" maceral vitrinite fusinite sporinite saturates, % 11.8 11.1 12.6 aromatics, % 13.2 15.2 25.1 monoesters, % 28.1 14.7 20.1 polar compounds, % 46.9 59.0 42.2 % of total extract; see Experimental Section and Figure 3 for details.
dichloromethane and water. The combined filtrates were extracted with dichloromethane and diethyl ether. The total extract was esterified with diazomethane and purified on a silica gel column by elution with diethyl ether (fraction E), diethyl ether/methanol 1:l (v:v) (fraction EM) and chloroform/methanol/water 65:25:4 (v:v:v) (fraction CMW). The former was further separated on thin layer chromatography by elution with dichloromethane into three fractions which grossly correspond t o aliphatic esters (RF = 0.6-LO), aromatic esters (RF= 0.1-0.6),and p o h (RF= 0.04.1). The two former fractions were then analyzed by GC and GC-MS (see conditions above).
Organic Extracts Results. Extraction yields are given in Table IV, for each extraction step and the total extracts. The extraction yields follow the unexpected order: vitrinite > sporinite > fusinite (respectively7.0, 3.5, and 1.1% of total extract). On the basis of Table IV, we can assume that there is no toluene/methanol extractible organic compounds left in fusinite and sporinite after four extraction steps. This is not the case for vitrinite, which presumably retains some extractible materials in its macromolecular matrix. Table V shows the result of fractionation of the organic extracts of the three macer& into saturated and aromatic hydrocarbons, as well as esterified acids. No systematic trend can be observed. The saturated hydrocarbon fractions are dominated by the n-alkanes (Figure 4). Their distributions are similar for vitrinite and fusinite, with a maximum around n-C,, in both cases. The predominance of the n-Czzhomologue For sporinite, in vitrinite can be due to ~ontamination.~~ the distribution of n-alkanes is rather different, with a shift toward higher molecular weight compounds and a slight odd-even predominance (n-CZ7, n-CZ9,n-C36,and n-C,,). This phenomenon is characteristic of higher plant origin and could reflect a lower level of maturity of extracted organic matter from sporinite, compared with vitrinite and fusinite. In the three cases, the pristanelphytane ratios reflect rather oxidative conditions of deposition (Pri/Phy (37) Douglas, A. G.; Grantham, P. J. Chem. Geol. 1973,12,249-255.
= 7.8, 5.9, and 8.3 for vitrinite, fusinite, and sporinite, respectively). The saturated hydrocarbon fraction extracted from sporinite is relatively enriched in isoprenoid hydrocarbons from C14 to C18 (as well as pristane and phytane). It also contains a relatively high amount of alkylcyclohexanes ranging from CIz to C17. The main difference between vitrinite and fusinite lies in their relative hopane concentrations: these components seem to be much more abundant in fusinite (they are rather scarce in vitrinite). Hopanes are also present in sporinite. Their carbon distributions, shown in Figure 5, are similar in the three cases: 17a(H),21p(H)are the major isomers and thermodynamic equilibrium at C-22 is reached. However, sporinite seems to be slightly enriched in 17P(H),21a(H)isomers, in comparison with vitrinite and fusinite. Gas chromatograms of the total aromatic hydrocarbon fractions (not given here) exhibit similar distributions for vitrinite and fusinite, with a large predominance of naphthalene methylated derivatives: dimethylnaphthalenes are the major isomers. For sporinite, naphthalene as well as phenanthrene methylated derivatives are the major components: MN, DMN, TMN, P, and MP all stand at the same level. Since naphthalene and phenanthrene methylated isomers have been extensively used to assess coal maturity,13338-40 we laid special emphasis on these components; their typical mass fragmentations in GC-MS are given in Figure 6 for naphthalene and its mono-, di-, tri-, and tetramethylated derivatives (mlz = 128,142,156,170, and 184, respectively), as well as for phenanthrene and its mono-, di-, tri-, and tetramethylated derivatives ( m l z = 178, 192, 206, 220, and 234, respectively). The results are indeed similar for vitrinite and fusinite, whereas sporinite exhibits different distributions. Figure 7 shows gas chromatograms of the methyl esters of the monoacids obtained after esterification of the acidic fractions of fusinite and sporinite. No monocarboxylic acid has been detected in vitrinite organic extract. In fusinite concentrate, a distribution of linear monocarboxylic acids from C12to cz8 is observed, with a large predominance of the stearic and palmitic acids (n-CI6and n-Cls). Hopanoic acids are also present. The acidic fraction from sporinite is rather simple, with a quasi-exclusive presence of hopa(38) Radke, M.; Welte, D. M. Adu. Org. Ceochem. 1981 1983,504-512. (39) Alexander, R.; Kagi, R. I.; Rowland, S. J.; Sheppard, P. N.; Chirila, T. V. Ceochim. Cosmochim. Acta 1985,49, 385-395. (40) Garrigues, P.; De Sury, R.; Angelin, M. L.; Bellocq, J.; Oudin, J. L.; Ewald, M. Geochim. Cosmochim. Acta 1988,52, 375-384.
Energy & Fuels, Vol. 5, No. 6, 1991 879
Study of Three Maceral Groups MN
T
P
a) Sporinlte
-
I
-
128
170
142 I
I
156
I
170
b) Vltrinlte and Fusinlte
192
I
208
I
220
I
234
p
I
II 1 TMP-
mi2
-
178
r T r llI-
Figure. 6. Carbon distributions of naphthalene methylated derivatives (m/z = 128,142,156,170, and 184)and phenanthrene methylated derivatives ( m / z = 178, 192, 206,220,and 234) occurring in the bitumen of (a) sporinite and (b) vitrinite and fusinite concentrates. See Figure 5 for chromatographic conditions.
noic acids. Hopanoic acids from both fusinite and sporinite exhibit similar carbon distributions (Figure 8, a and b, mass fragmentograms m/z = 191 in GC-MS): Cm,C31,and C32homologues are the only components, with a large predominance of 17a(H),21@(H)isomers although 17P(H),Zla(H) isomers are also present. Thermodynamic equilibria at C-22 seem to be reached.41 Discussion. The presence of hopanoic acids in fusinite organic extract and their absence in vitrinite is in agreement with observations made on hopane concentrations in the saturated hydrocarbon fractions of these two macerals. A valuable explanation could be found in a difference of bacterial input between the two macerals. As a matter of fact, extended hopanoid compounds are known to find their origin in microorganisms such as bacteria and blue-green algae.16 Fusinite comes from plant tissues which have undergone air oxidation or aerobic bacterial degradation, whereas rapid protection against these phenomena would have led to gellified vitrinite. In our case, a rather strong bacterial degradation of plant tissues yielded "degradofusinite", in opposition with "pyrofusinite", which is the name of fusinite obtained under forest fire degradation.44 The great variations observed between the distributions of the saturated and aromatic hydrocarbons of sporinite on the one hand and vitrinite and fusinite on the other could be explained in terms of the source of organic matter. Furthermore, the presence of hopanoids and alkylcyclohexanes in sporinite reflects a substantial bacterial contribution. The carbon preference index (CPI),46as well as methylnaphthalene and methylphenanthrene indic(41) Jaff6, R.; Albrecht, P.; Oudin, J. L. Org. Geochem. 1988, 13, 483-488. (42) Seiiert, W.K.; Moldowan, J. M. Geochim. Cosmochim. Acta 1978, 42. ~- 11-95.
'(43) Zhao-An, F.; Philp, R. P. Org.Geochem. 1987, 11, 169-175. (44) Chiche, P. Entropie 1983, 113-114, 16-42. (45) Bray, E. E.; Evans, E. D. Geochim. Cosmochim. Acta 1961,22, 2-15.
a) Fuslnlte
I
I
v
linear monocarboxylic acids
k.
i
hopanoic acids
1
n
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b, Sporlnlte
-
hopanoic acids
Figure 7. Gas chromatograms of monocarboxylic acids (as their methyl esters) occurring in the bitumen of (a) fusinite and (b) sporinite concentrates. See Figure 4 for chromatographic con-
ditions.
es,133seems to indicate a lower degree of maturity for the bitumen extracted from sporinite. As we will see below, observations going into the same direction can be deduced from our results obtained on the macromolecular matrix. It should, however, be kept in mind that the CPI can be heavily source influenced. Furthermore, rank parameters
Blanc et al.
880 Energy & Fuels, Vol. 5, No. 6,1991 a) Fusinite : extraction
b) Sporinite : extraction
c) Sporinite : oxldatlon
N
2 I
T"C
Figure 8. Mass fragmentograms m / z = 191 of the hopanoic acids (as their methyl esters)-occurring in the bitumen of (a) fusinite, (b) sporinite, and (c) in oxidation products after treatment of sporinite with ruthenium tetroxide. See Figure 5 for chromatographic conditions. a) Sporlnlte
Table VI. Yields of Products of Oxidation of Macerals with Ruthenium Tetroxide. Fractions Eluted with Diethyl Ether (E), Diethyl Ether/Methanol 1:l (EM), and Chloroform/Methanol/Water 65:25:4 (CMW)" maceral vitrinite fusinite sporinite fraction E, % 10.3 1.1 8.1 fraction EM,% 15.7 23.5 60.8 fraction CMW,% 19.3 4.5 24.8 total, % 45.3 29.1 93.7 a
RF
= 0.6
-
1.0
c,
c!l
v
C!¶
LINEAR MONOACIDS
'70 of extracted maceral; see Experimental Section for details.
based on alkylaromatic hydrocarbons, such as naphthalene and phenanthrene, have been shown to work extremely well in the case of type I11 organic matter but are of more delicate use in the case of type I1 organic matter to which our sporinite belongs based on elemental analysis and Rock-Eva1 pyrolysis. The presence of linear monocarboxylic acids in fusinite organic extract is rather unexpected. The large amount of stearic and palmitic acids is also inexplicable. Although these compounds are well-known to be present in high quantities in plants,34 their predominance should be drastically reduced at this stage of maturation (0.84% R, for the original coal). It should be noted that these two acids have been found to be the major components of the acidic fractions obtained in several kinds of studies on coals and kerogens of varied origins and maturities: extraction or l i q u e f a c t i ~ np, y~ r~o~l y~s~i ~~, ~x ~i d a t i o n . *This ~ * ~ wide~ spread occurrence raises the problem of their origin or pathway of formation: the possibility of their existence as artifacts should be taken into account, unless they reflect a special microbial contamination. Oxidative Degradation of Macromolecular Matrix Results. Yields of ruthenium oxidation of the solid residues obtained from solvent extraction of the three macerals are given in Table VI. They are expressed as weight percentage of fractions of increasing polarity (respectively fractions E, EM, and CMW). The total yields indicate that sporinite is the easiest degradable (93.7%), maybe due to the great capability of the reagent to enter its macrostructure. Oxidation of sporinite yields a high amount of polar compounds. In contrast, fusinite seems (46)Dong, J. Z.;Katosh, T.; Itoh, H.; Ouchi, K. Fuel 1987, 66, 1336-1346. - - - . - - ..
(47)Almendros, G.;Gonzalez-Vila,F. J.; Martin, F.; Alvarez-Ramis,
C. Fuel 1988,67,502-507.
(48)Kawamura, K.; Tannenbaum, E.; Huizinga, B. J.; Kaplan, I. R.
Org. Geochem. 1986, 10, 1059-1065.
I 4a
1M
150
m
250
3w
1%
b) Sporlnlte
LINEAR DIACIDS
+
I
40
1W
150
zm
250
300
T'C
Figure 9. Gas chromatograms of (a) monocarboxylic and (b) dicarboxylic and aromatic acids (as their methyl esters) in oxidation products after treatment of sporinite with ruthenium tetroxide. Conditions: SE54, 30 m X 0.32 mm, 40-300 O C , 3 O C/ min.
to resist oxidative degradation: the yields are low and cloee to those obtained from a high-rank vitrinite-rich coal, Escarpelles (2.45% R,).13 This could be due to the high level of condensation of this maceral, which prevents the reagent from reaching the oxidation sites. In this study, we have essentially concentrated on the analysis of aliphatic and aromatic acids (as their methyl esters) contained in fraction E (cf. Experimental Section). These compounds represent 6.0,5.9, and 0.9 wt% of the preextracted sporinite, vitrinite, and fusinite concentrates, respectively. Three families of compounds have been considered: linear mono- and dicarboxylicacids, hopanoic acids, and benzenepolycarboxylic acids. In the case of sporinite, the main oxidation products are linear monocarboyxlic and a,w-dicarboxylicacids. Figure
Energy & Fuels, Vol. 5, No. 6, 1991 881
Study of Three Maceral Groups 9a shows the gas chromatogram of the least polar fraction (RF = 0.6-1.0; CH2C12),dominated by linear monocarboxylic acids from Cgto C33,with a maximum around CI3. This distribution is quite different from the distribution of free monocarboxylic acids contained in the organic extract (cf. Figure 7b). This gives evidence for a neoformation of these compounds through oxidative cleavage of aliphatic entities linked to a polyaromatic n e t w ~ r k . ’Hence, ~ ~ ~ the sporinite macromolecular matrix seems to be rich in long aliphatic side chains. Short aliphatic bridges of hydroaromatic entities are also present in this matrix, reflected by the short linear dicarboxylic acids observed in the more polar fraction corresponding to aromatic acids (RF = 0.1-0.6; CH2C12). Their gas chromatogram is shown in Figure 9b; they exhibit a carbon distribution from C5to C13 with a maximum around C7-C8. The C8 homologue coelutes with phthalic acid (benzene1,2-dicarboxylic acid) which is the major aromatic component with trimellitic (1,2,4-tricarboxylic) and hemimellitic (1,2,3-tricarboxylic) acids. These aromatic acids are supposed to be the stable end oxidation products of polyaromatic en ti tie^.'^^^^ Their weak occurrence in the oxidation products of sporinite macromolecular network shows the low amount of this type of structure in the latter. Hopanoic acids have been found among the oxidation products obtained after treatment of sporinite with ruthenium tetroxide. Their carbon distribution is shown on Figure 8c (mass fragmentogram m/z = 191) and is very different from the one of free hopanoic acids contained in the organic extract (cf. Figure 8b). Here again, this difference plays in favor of a neoformation of these compounds from oxidative cleavages of hopanes covalently linked by their side chain to polyaromatic unit^.'^,^^ Comparison between free and bound hopanes shows differences for C-22 epimerization: in particular, the 22S/22R ratio for the C31 bound hopanes (C32 hopanoic acids on Figure 8c) is much lower than that of the corresponding CB1-freehopanes (Figure 512). This tendency was observed over a wider carbon number range (c31-c33)after Ru04 oxidation of the whole Vouters coal.13 Two explanations are possible: the C-22 epimers of bound hopanes may have equilibrium ratios differing from those of the free hopanes due to their linkage to a macromolecular network or they may be protected from epimerization by the latter. In any case these ratios may further be influenced by the length of the side chain. Similar results have been previously reported from pyrolysis of petroleum asphaltenes and as well as hydrogenolysis of bituminous ~oa1.~~-~~ No linear carboxylic acid could be detected after oxidation of vitrinite and fusinite. The main oxidation products are benzenepolycarboxylic acids, containing from two to six carboxylic groups (Figure 10). These compounds are the major oxidation products of humic ~0als.l~” Methylated and methylenecarboxylic homologues are also present in lesser amounts. The distribution in the case of fusinite is largely dominated by phthalic acid; the other homologues are present in lower amounts which could be due to a difficulty for the reagent to enter the macromo(49) Rubinstein, I.; Sprckerelle, C.; Strausz, 0. P. Geochim. Cosmochim. Acta 1979,43, 1-6.. (50) RullkBtter, J.: Aizenshtat. 2.; Spiro. B. Geochim. Cosmochim. Acta 1984,48, 151-157. (51) Tannenbaum, E.; Ruth, E.; Huizinga, B. J.; Kaplan, I. R. Org. Geochem. 1986, I O , 531-536. (52) Van Graas,.G. Org. Geochem. 1986, I O , 1127-1135. (53) Shaw, P. M.; Eglinton, G. 1987International Conference on Coal Science; Elsevier: New York, 1987; pp 53-56. (54) Shaw, P. M.; Brassell, S.C.; Assinder, D. J.; Eglinton, G . Fuel 1988,67, 557-564.
j~ a) Vltrlnltr
RF
=
0.1
- 0.6
AROMATIC ACIDS
i
(00
40
IY)
200
b) Fuslnlte
&=+
RF
= 0.1 - 0.6
AROMATIC ACIDS
Figure 10. Gas chromatograms of aromatic acids (as their methyl esters) in oxidation products after treatment of (a) vitrinite and (b) fusinite with ruthenium tetroxide. See Figure 4 for chromatographic conditions.
lecular matrix and degrade large and condensed polyaromatic units. The major peak seen in Figure 10b (oxidation of fusinite) corresponds to a contamination introduced during the preparation of diazomethane used for esterification. We have shown recently that the distribution of benzenetetracarboxylic acid isomers in the oxidation products obtained by treatment of a set of French coals with ruthenium tetroxide can be used to establish parameters reflecting the condensation and aromatization of coal macromolecular network taking place with increasing coa1ifi~ation.l~The detailed results of this new approach have been reported elsewhere.55 The principal data obtained on macerals are given in Figure 11which represents, in particular, the three possible isomers (acids G, H and I) and the hypothetical structural units of the polyaromatic matrix from which they could stem. Acid I (benzene1,2,3,5-tetracarboxylic acid) comes from the oxidation of a diphenyl type unit which is supposed to disappear with increasing m a t u r a t i ~ ntherefore, ;~~ this acid should tend to decrease in coals of increasing maturity. Rank parameters are established as ratios between acids coming from condensed structural units (e.g., acid G)and acids coming from less condensed structural units (e.g., acid I). Since they are established from structural subunits belonging to the macromolecular network of coals, we called them “parameters of macromaturity” (PMM). Figure 11shows the benzenetetracarboxylic acid distributions obtained after treatment of the three macerals with ruthenium tetroxide (mass fragmentogram m / z = 279). In the mixture of the three isomers, the relative proportion of acid I follows the decreasing order: sporinite > vitrinite > (55) Blanc, Ph.; Albrecht, P. Org. Geochem. 1991,17,913-918. (56) Hatcher, P. G.; Schnitzer, M.; Vassallo. A. M.; Wilson, M. A. Geochim. Cosmochim. Acta 1989, 53, 125-130.
882 Energy & Fuels, Vol. 5, No. 6,1991
l
1
G
H
H
t
Blanc et al.
I
a) Black WP1.I
(0.07 %R,)
IH
0)
R II
N
2 l
- c)*
-TT
T'C
T"C
a) Sporinite
Fusinite
b) Vitrinite
b) Vouters (0.84 %R,)
=
+w--w w prehnitic acid
pyromellilic
w
acid
w
melloDhlanic acid
):R
~ cleavage O ~
Figure 11. Types of aromatic structural subunits of coals or macerals as potential precursors of benzene tetracarboxylic acids obtained by treatment with ruthenium tetroxide, and mass fragmentograms m / z = 279 of the benzene tetracarboxylic acids (as their methyl esters) in oxidation products after treatment of (a) sporinite, (b) vitrinite, and (c) fusinite with ruthenium tetroxide. See Figure 5 for chromatographic conditions.
fusinite, whereas acids G and H tend to increase when going from sporinite to fusinite. In particular, a great similitude of distribution has been observed between the fusinite concentrate of Vouters coal and the vitrinite-rich semianthracite from Escarpelles (2.45% PMM have been calculated for the three macerals; they follow the decreasing order fusinite > vitrinite > sporinite, thus reflecting the higher level of condensation of the polyaromatic network of the former (e.g., values of 2.08, 1.24, and 0.84 were obtained respectively for PMM6; see also Figure 13). Discussion. The oxidation products of the macromolecular matrix of sporinite reflect the high aliphatic character of this maceral. This is in good agreement with elemental analysis, as well as Rock-Eval pyrolysis results (cf. Tables TI and 111) which indicate type I1 organic matter, relatively rich in hydrogen (hydrogen index HI = 663 mg/g of TOC). Previous studies showed the massive presence of long polymethylene moieties in liptinite macerals, either by 'H NMR or p y r ~ l y s i s . ~ ' Sporinite *~ of Vouters coal seems to be made in particular of long aliphatic chains linked to small (po1y)aromatic units; this (57) Calkins, W. H.; Hovsepian, B. K.;Dyrkacz, G.R.; Bloomquiet, C. A. A.; Ruscic, L. Fuel 1984,63, 1226-1229. (58) Calkins, W. H.; Spackman, W. Int. J . Coal Ceol. 1986, 6, 1-19.
Figure 12. Comparison of gas chromatograms of ruthenium tetroxide oxidation producb from (a) Black Water and (b)Vouters coals. See Figure 4 for chromatographic conditions.
model is close to the one proposed by Hayatsu et al.&who studied sporinites by NMR, FTIR, Py-CG-SM, as well as chemical degradations (KMn04,HN03, NaOH), and who found that aromatic and phenolic entities are rather rare in comparison with aliphatic chains. This model could be only partly true; as a matter of fact, the possibility of the existence of aliphatic moieties linked to each other through ether or ester functionalities cannot be totally excluded, according to the results of the treatment of the highly aliphatic and immature Messel shale kerogen with ruthenium tetroxide3'j (Blanc et al., manuscript in preparation). Vitrinite and fusinite macromolecular networks seem to be poor in aliphatic moieties. Their oxidation products reflect the high aromatic character of these macerals in comparison with sporinite. This is in agreement with type I11 or degraded organic matter as indicated by elemental analysis and Rock-Eval pyrolysis. Oxidation products of the whole Vouters coal reflect the contribution of its liptinite fraction (cr,o-dicarboxylic acids on Figure 12b) and its vitrinite and inertinite fractions (aromatic acids in the same figure). In addition, the analysis of the corresponding fraction obtained from the liptinite poor (1.6 ~01%)Australian Black Water coal (0.97% I?,,) shows the lack of the a,w-dicarboxylic acids (Figure 12a), thus confirming that the latter really come from the degradation of methylene bridges or hydroaromatic entities which seem to be specific of the liptinite macerals at this maturation stage. PMM values for the three macerals showed that fusinite had the most condensed polyaromatic entities. For a better illustration of the eventual utilization of these parameters we have tried to correlate the PMM values with (59) Hayatsu, R.; Both, R. E.; McBeth, R. L.; Scott, R. G.; Winane, 1988,2, 843-847.
R. E.Energy Fuels
Energy & Fuels, Vol. 5, No. 6,1991 883
Study of Three Maceral Groups PMM 6 PMM 6
=E
5
v n-alkanes
vltrinite sporinlte
0.67
,
1.08
1.94
3
%Ro
Figure 13. Application of parameter of macromaturity to macerals. See Figure ll for details; Pr, Vo, Me, Es = French coals; BWI, CCFl = Australian coals.
fictitious reflectance R, values based on a set of samples composed of four vitrinite-rich French coalsI3 and two inertinite-1 rich Australian coal^.^ The inertinite content of the latter is around 40 ~ 0 1 % .Their PMM values are higher than those that should be obtained from vitriniterich coals having their vitrinite reflectance values. This means that the macromolecular networks of these inertinite-rich coals are more condensed and aromatic than expected on the basis of their vitrinite reflectance values. Fictitious vitrinite reflectance values for the three macerals can be obtained from the regression line between PMM and %R, of the coals; as a result fusinite would behave like a 1.94% R, coal, against 1.08% R, for vitrinite and 0.67% R, for sporinite, based on the data from PMM6 (Figure 13). These results are in agreement with known optical properties of the three maceral groups, inertinites being high reflecting, liptinites low reflecting, and vitrinites intermediate.@ In addition, real vitrinite reflectance value of the raw coal (0.84% RJ is relatively close to the fictitious one from vitrinite concentrate (1.08% RJ and behaves like an average from the three fictitious values. However, this coal contains some micrinite which has not been studied in our work. Oxidation yields of the three macerals indicate that sporinite is easily chemically degradable at this rank, whereas fusinite is rather resistant, due to its high level of condensation and aromaticity. These results from chemical degradation are confirmed by those from thermal degradation in Rock-Eval pyrolysis experiments. The high amount of hydrocarbons obtained from cracking of the macromolecular matrix of sporinite (S, = 453 mg of HC/g) shows this maceral is thermally fragile as well as oil prone, due to its high aliphatic character. The S2value for vitrinite (118 mg of HC/g) could be representative of a raw bituminous coal of Northern hemisphere. As far as fusinite is concerned, it is more resistant than the two other macer& toward thermal degradation: T,, is higher (440 "C for fusinite against 424 and 422 "C for vitrinite and sporinite, respectively) and S, is very low (29 mg of HC/g). The latter is intermediate between the values obtained from a late catagenesis coal, such as MBricourt (1.419% R,; S2= 56 mg of HC/g) and a semianthracite one, Escarpelles (2.45% R,; S , = 9 mg of HC/g). Organic carbon recordings during pyrolysis between 300 and 600 "C (pyrolyzed carbon, PC) corroborate the above results PC is very high for sporinite (38.1%) and very low for fusinite (2.0%, to be compared with 0.7% for the anthracitic coal, Escarpelles). These results reflect the great level of thermal volatility of sporinite and the low one of fusinite. An estimation of the level of thermal volatility of the three macerals can be obtained by the ratio (S, + (60) Teichmiiller, M. Org. Geochem. 1986, 10, 581-599.
c
50
100
150
Temperature (OC)
Figure 14. Gas chromatograms of light hydrocarbons (C5-C13) obtained after thermodesorption of (a) vitrinite and (b) fusinite concentrates. Conditions: Apiezon L, 30 m, 40-160 "C, 2 OC/min. (a) 2-Methylpentane, (b) methylcyclopentane, (c) benzene, (d) cyclohexane, (e) methylcyclohexane,(f) toluene, (g + h) m-and p-xylene, (i) o-xylene.
S2 + S3)/TOC: it follows the decreasing order: sporinite >> vitrinite > fusinite (69.7, 18.8, and 6.4%, respectively, of thermal volatilization at 600 "C). Similar results have been obtained by Pandolfo et al.,6* who analyzed maceral concentrates from a bituminous Gondwana coal: the weight loss after pyrolysis at 600 "C were 95,35, and 30% for liptinite, vitrinite, and inertinite, respectively. Moreover, recent results from Schenck et go into the same direction; they showed that the maximum pyrolytic weight loss (up to 670 "C) amounts to 60% of the initial organic matter in the case of a vitrinite from an immature German lignite (H/C = 1.14) and to 85% in the case of a Tasminite alginite (H/C = 1.60). Finally, we have checked the greater aromaticity of fusinite compared with vitrinite by means of thermodesorption of light hydrocarbons at 220 "C during 10 min under helium stream. Gas chromatograms of the C, to C13 range indeed show a higher relative concentration of monoaromatic compounds in fusinite (peaks c, f, g, and h in Figure 14b), whereas cycloalkanes are more predominant in vitrinite (peaks b, d, and c in Figure 14a). A novel aromaticity factor could even be developed in this respect by making for instance the following ratio (benzene + toluene)/(cyclohexane + methylcyclohexane) (e.g. c + f/d + e in Figure 14; a similar ratio has been used previously for studying migration of hydrocarbons in the subsurface63). A more accurate value of this ratio could eventually be obtained by changing the chromatographic conditions or using selected ion detection in GC-MS. Conclusions Most of the variations observed between the distributions of saturated and aromatic hydrocarbons of the three macerals of the Vouters coal can be interpreted in terms of source of organic matter and early diagenetic processes. (61) Pandolfo,A. G.; Johns, R. B.; Dyrkacz, G. R.; Buchanan, A. S. Energy Fuels 1988,2, 657-662. (62) Schenk, H. J.; Witte, E. G.; Littke, R.; Schwochau, K. Adu. Org.
Ceochem. 1989 1990, 943-950. (63) Schaefer, R. G.; Leythaeuser, D.; Von der Dick, Geoch. 1981, 1983, 164-174.
H. Ado. Org.
884 Energy & Fuels, Vol. 5, No. 6, 1991
Significant amounts of hopanes in fusinite, of hopanes and alkylcyclohexanes in sporinite reflect a substantial reworking by microorganisms. The usual rank parameters based on molecular markers contained in the organic extracts of the macerals showed no significant difference between vitrinite and fusinite fractions from the Vouters high-volatile bituminous coal. These parameters seem to indicate a lower degree of maturity for the sporinite. This conclusion has, however, to be taken with caution because most of these parameters (carbon preference index of n-alkanes, moretane/hopane ratio, n-alkaneslhopanes ratio) can also be source dependent. Furthermore, the parameters based on alkylaromatic hydrocarbons are known to be accurate only in type I11 organic matter which id not the case of sporinite whose characteristics place it in type 11. These results confirm the fact, previously mentioned by Puttmann et a1.,l0 that some parameters used for organic geochemical studies of whole coals can be influenced by their maceral composition. The main molecular difference between vitrinite and fusinite is their hopanoid concentrations: hopanoids (hopanes as well as hopanoic acids) are more abundant in organic extract of fusinite which could indicate a high bacterial reworking for fusinite whereas vitrinite has been protected from it. This bacterial contribution may reflect fusinization phenomenon leading to degradofusinite. Oxidation products after treatment of the macromolecular networks of the macerals with ruthenium tetroxide reflect the high aliphatic character of sporinite (which yields essentially linear mono- and dicarboxylic acids) and the highly aromatic characters of vitrinite and fusinite (which yields essentially aromatic acids). Both oxidative degradation and Rock-Eva1pyrolysis show sporinite to be easily degradable and fusinite very resistant, at this level of maturation. Covalently bound hopanes have been found in sporinite macromolecular matrix which seems to reduce or modify thermodynamic equilibrium at (2-22. The lack of these compounds in vitrinite and fusinite could be explained by a lack of bacterial input for the former and an incorporation of hopane structures in a condensed and highly aromatic macromolecular network for the latter. New coal rank molecular parameters based on structural subunits belonging to the macromolecular network (PMM, parameters of “macromaturity”) have been proven to be more discriminating than rank parameters obtained from extracted molecular markers. Furthermore, they could be more reliable since they are less influenced by oil generation and migration phenomena or biodegradation. They enabled the quantification of the level of condensation of the polyaromatic network of the macerals. The following order has been observed fusinite > vitrinite > sporinite. Moreover, some similarities have been observed between the macromolecular networks of fusinite from the highvolatile bituminous coal (0.84% R,) and the vitrinite-rich semianthracitic coal of Escarpelles (2.45% R J . PMM values indicate that fusinite seems to behave like a 2% R , vitrinite-rich coal. This similitude between some low-rank inertinites and higher rank vitrinites have been already observed in previous studies:61-a fusinite seems to have undergone an artificial accelerated maturation, perhaps under a strong aerobic degradation. Recent results on the same maceral fractions as those analyzed in our study support this conclusion. Indeed, microtextural study of (64) Nip, M.;De Leeuw, J. W.; Schenck, P. A. Ceochim. Cosmochim. Acta 1988,52, 637-648.
Blanc et al. fusinite having undergone pyrolysis (Rouzaud et al., unpublished results@)as well as analysis of the same maceral submitted to confined pyrolysis in a gold tubew showed that fusinite behaves like a vitrinite of higher rank. Furthermore, 13CCP/MAS NMR measurements obtained on macerals isolated from Vouters coaP7 confirmed this assumption since the corresponding aromaticity factors (fa) have respective valus of 0.85,0.80 and 0.68 for inertinite, vitrinite, and liptinite. As a reminder, the value of f a for the vitrinite-rich high-rank Escarpelles coal is 0.89. Some industrial applications of these organic geochemical results could be considered in the coking field, since it is well-known that the coking behavior of coals or coal mixtures largely depends upon their maceral composition. Our results show that the behavior of macerals during pyrolysis is reflected in their chemical composition. The high aliphatic character of sporinite corresponds to high softening properties during coking. On the opposite, the high level of condensation and aromaticity of fusinite could explain its noncoking properties. To an extent, PMM values could help in differentiating inertinites as far as their behavior during pyrolysis is concerned. Indeed, although inertinites were generally considered to be unreactive during the coking process, several studies have recently developed the concept of reactive inertinites, mainly on the basis of optical observations.6g70 Our studies of the molecular structure of macerals may be used to predict reactivity during carbonization and deliver a valuable explanation of this phenomenon on the basis of chemical concepts. For example, an inertinite maceral showing very high PMM values after RuOl oxidation (e.g., comparable to an anthracite) will represent a really unreactive material due to its highly condensed polyaromatic structure. On the other hand, rather low PMM values (e.g., of the same order of magnitude as for a highly volatile bituminous coal) will reflect an inertinite with an aptitude to undergo significant changes during carbonization. In the first case the maceral may be used as a fibrous component of the coal mixture, whereas in the second case it will act as a reactive component. A better knowledge of these properties might be important in defining the coal blend for the coking process.
Acknowledgment. We thank the Centre de Pyrolyse de MariBnau, and the Centre National de la Recherche Scientifique (CNRS) for research fellowship (P.B.) and financial support in the frame of the G.S. “Pyrolyse du Charbon”. We are grateful to F. Marquis, E. Lichtfouse, and F. Behar who enabled the Rock-Eva1 pyrolysis experiments at the Institut Fransais du PBtrole, as well as to P. Landais (Centre de Reherche sur la GBologie de l’uranium, Vandoeuvre-les-Nancy)and R. G. Schaefer and H. J. Schneck (Kernforschungsanlage, Julich) for fruitful information. We also thank P. Quilliacq (SociBt4 Nationale Elf-Aquitaine (Production), Pau) for the thermodesorption experiments. Registry No. RuO,, 20427-56-9;phthalic acid, 88-99-3; trimellitic acid, 52844-9; hemimellitic acid, 569-51-7;prehenilic acid, 479-47-0;pyromellitic acid, 89-05-4;mellophthanic acid, 479-47-0. (65) Muller, J. F.;Abou Akar, A.; Kohut, J. P. Advanced Methodologies in Coal Characterization; Elsevier: New York, 1990; pp 359-398. (66) Landais, P.;Kohut, J. P.; Michels, R.; Muller, J. F.; Oudin, J. L.; Zaugg, P.Fuel 1989,68, 1616-1619. (67) Tekely, P.;Nicole, D.; Delpuech, J. J. Advanced Methodologies in Coal Characterization; Elsevier: New York, 1990, pp 135-147. (68) Diessel, C.F. K. Fuel 1983, 62, 883-892. (69) Dieasel, C.F.K.; Wolff-Fiacher,E. 1987 International Conference on Coal Science; Elsevier: New York, 1987; pp 901-906. (70) Kurszewska, K. Fuel 1989,68, 753-757.
