Artificial maturation of a high volatile bituminous coal from

Asturias (NW Spain) in a confined pyrolysis system

Part I. Petrographic, geochemical and molecular studies

Noe Piedad-Sanchez a, Luis Martınez a,*, Alain Izart a, Isabel Suarez-Ruiz b,Marcel Elie a, Cedric Menetrier a

a UMR G2R/7566 - Geologie et Gestion des Ressources Minerales et Energetiques, Faculte des Sciences,

Universite Henri Poincare, Nancy 1, BP-239, Boulevard des Aiguillettes, 54506 Vandoeuvre-les-Nancy Cedex, Franceb Instituto Nacional del Carbon (INCAR), CSIC, Ap.Co., 73: 33080 Oviedo, Spain

Received 7 June 2004; accepted 22 December 2004

Available online 7 April 2005

www.elsevier.com/locate/jaap

J. Anal. Appl. Pyrolysis 74 (2005) 61–76

Abstract

The objective of this work is to estimate the hydrocarbon production in the Central Asturian Coal Basin (NW Spain) by using:

� th

*

01

do

e maturation simulation of the coal in laboratory by confined

pyrolysis, and

� th

e study of the petrographic (%Rr), geochemical (Tmax) and

molecular changes during the artificial maturation process.

Confined pyrolysis was carried out inside gold cells under a pressure of 700 bar at several temperatures (330, 360 and 400 8C) and

durations (24, 120 and 720 h).

Artificial maturation from lower to higher temperature showed an evolution of macerals by comparing the raw coal and the solid residues

after the pyrolysis. The vitrinite content increases and the inertinite and liptinite contents decrease. The porosity also increases with an

increase of the pore size and eventually, coalesces. The vitrinite reflectance (%Rr) increases from 0.78 for the raw sample to 2.98 for the solid

residues at 400 8C.

Organic geochemical parameters exhibit a similar trend with an evolution from oil window to the gas window. HI and Tmax of original coals

of this basin indicate a predominant gas- to oil-proneness.

A decrease of total extract yields and changes in aliphatics, aromatics and polars contents is also showed by increasing maturation.

Aromatization reactions transform aliphatic and polar molecules at high temperature.

# 2005 Elsevier B.V. All rights reserved.

Keywords: Artificial maturation; Confined pyrolysis; Coal gas; Central Asturian Coal Basin

1. Introduction

The Central Asturian Coal Basin is a mining district

(Fig. 1), located in the Cantabrian Mountains zone (NW

Spain). High volatile bituminous to anthracitic coals are

currently worked in different underground mines by

HUNOSA Co. ‘‘Marıa Luisa Pack’’ from the Pumarabule

Corresponding author. Tel.: +33 383 684748; fax: +33 383 684701.

E-mail address: luis.martinez@g2r.uhp-nancy.fr (L. Martınez).

65-2370/$ – see front matter # 2005 Elsevier B.V. All rights reserved.

i:10.1016/j.jaap.2004.12.012

mine, in the north part of the basin from the ‘‘La Justa-

Aramil and Caudal-Nalon Unit’’, contains one of the

commercial coal seams with the maximum thickness. The

Central Asturian Coal Basin is almost exclusively made up

of carboniferous sediments up to 6000 m thick of alternate

marine and continental origin [1,2]. Colmenero and Prado

[3], and Alonso and Brime [4] reported some data related to

the maturation of the region. Organic petrography and

molecular analysis of the basin [5–8] suggest a swamp

environment with a vitrinite-rich facies, variable ash, and

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7662

Fig. 1. Structural map of the Central Asturian Coal Basin (data from HUNOSA, Co. and ref. [2]).

low sulfur content located on a delta plain with a relatively

high water table [8]. Moreover, for this basin, Piedad-

Sanchez et al. [7] reported a regional thermal gradient

described by the addition from a normal geothermal gradient

and a thermal igneous flux, in agreement with early

observations established by Colmenero and Prado [3].

The evolution process of the organic matter is mainly a

function of the temperature and time increase. Stach et al.

[9] have demonstrated that it is possible to simulate the

natural maturation process at the laboratory scale by

increasing temperature to shorten reaction time. Peters et al.

[10], Rohrback et al. [11], and Huang [12], among others,

have simulated maturation processes through experimental

maturation studies in the laboratory. Monthioux et al. [13],

Landais and Monthioux [14], Landais et al. [15,16],

Benkhedda et al. [17], Gerard et al. [18], Mansuy and

Landais [19], Mansuy et al. [20], Michels et al. [21–23],

Landais and Gerard [24], and Han et al. [25] have

also shown that this maturation technique is able to

reproduce the thermal transformation of kerogen and the

generation of oil and gas according to natural evolution

trends.

The present work is focused on the artificial evolution of a

high volatile bituminous coal selected from the Pumarabule

coal mine (Fig. 1), the main objective being: (i) to study the

petrographic (%Rr), geochemical (Tmax) and molecular

changes of the selected coal obtained by confined pyrolysis

maturation, and (ii) to evaluate the hydrocarbon potential

generation of this basin through geochemical and molecular

techniques. The part II of this paper [75] will be focused on

gas production during the artificial maturation compared

with a simulation.

2. Methodology

2.1. Confined pyrolysis

A coal sample of Pumarabule mine from the Central

Asturian Coal Basin, previously studied by Piedad-Sanchez

et al. [8], was selected for the experimental maturation. The

sample is a vitrinite-rich coal with a reflectance of 0.78%.

Artificial maturation was performed by using a confined

pyrolysis system [13–16,26,21,23]. Fig. 2 shows a schematic

diagram followed for the confined artificial maturation

experiments. Nine sets of 1 g aliquot of the powdered coal

sample were loaded under an inert atmosphere into gold

cells (L = 5 cm, I.D. = 1 cm). Previously vacuum dried, the

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 63

Fig. 2. Confined artificial maturation schema performed on a selected coal sample of the Pumarabule mine from Central Asturian Coal Basin.

gold cells were sealed under argon and atmospheric

pressure. The gold cells were placed into the high-pressure

autoclaves and isothermally heated at different periods of

time and temperature: 24 h at 330 8C for two gold cells, at

360 8C for one gold cell, and at 400 8C for one cell,

respectively. Three gold cells were pyrolysed for 120 h at the

same temperatures, and finally, and three gold cells were

pyrolysed for 720 h at the same range of temperatures

(Fig. 2). The temperature was controlled by an internal

thermocouple in contact with the gold cells

(accuracy � 1 8C). A hydrostatic pressure of 700 bar was

maintained during all experiments. At the end of the

processes the gold cells were recovered and carefully

cleaned with hot chloroform for 1 h, then pierced and kept to

measure the weight loss.

2.2. Petrographic analysis

The solid residues obtained from the pyrolysis processes

were prepared for petrographic analysis [27,28]. Optical

characterization performed was a maceral analysis and mean

random vitrinite reflectance measurement. Both types of

determinations were carried out on a MPV-Combi Leitz

microscope in accordance with ISO 7404-3 [29] and ISO

7404-5 [30] standards respectively. A qualitative fluores-

cence characterization using blue-violet light was performed

in a modified MPV2-Leitz microscope.

2.3. Geochemical characterization

The geochemical characterization performed on the coal

included chemical conventional analysis, Rock-Eval pyr-

olysis, and gas chromatography/mass spectrometry (GC/

MS).

Moisture, ash and volatile matter contents of the coal and

solid residues were determined by using a TGA-601 Leco

apparatus. The C, H, N and total sulfur contents were

determined by using a CHNS-932 Leco microanalyzer.

For the raw coal, the Rock-Eval analysis was performed

in a Turbo Rock-Eval model RE6 following the procedure

described by Espitalie et al. [31–33].

GC/MS analysis were carried out on the solvent

extractable fraction of the raw coal as well as the solid

residues obtained from the pyrolysis at each sample except

the sample obtained at 400 8C for 720 h because of its low

mass. The samples were extracted by using chloroform at

60 8C for 45 min by using the Accelerator Solvent

Extraction ASE200, and then fractionated into saturated,

aromatics hydrocarbons and NSO compounds by means of

liquid chromatography on a silica column. The saturated and

aromatic hydrocarbons were analyzed by GC–MS using a

Hewlett-Packard 5890 Series II, and a Hewlett-Packard-

5971 mass selective detector (MSD) with an ionising voltage

of 70 eV, operating on ‘‘fullscan’’ and ‘‘single ion’’ (SIM)

modes. The procedure used was that previously reported by

Radke [34], and Fleck et al. [35].

3. Results and discussion

3.1. Petrography

The raw coal [8] shows high vitrinite (82.8 vol.%) and

low mineral matter contents (4.6 vol.%) and a collotelinite

and collodetrinite predominance followed by others

macerals (e.g., sporinite and resinite). Laboratory matura-

tion contributes to a higher vitrinite content and an increase

of the vitrinite reflectance (Fig. 3A, Table 1). The increase in

vitrinite reflectance implies increased maturation.

Fig. 4A and B shows the porosity data after Hg

porosimetry of the raw coal sample. The coal sample

exhibits a porosity of 3.95% and a pore volume of 0.031 g/

cm3, with a ‘‘bulk’’ density (pore diameter < 12 mm) about

1.288 (g/cm3) and ‘‘real’’ density (pore diameter < 6 nm)

about 1.341 (g/cm3). In this way, the porosity of the coal

sample would allow an active diffusion mechanism [36]

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7664

Fig. 3. (A) %Rr vs. time, and (B) %Rr vs. temperature of artificial maturation of one coal sample from Pumarabule mine (Central Asturian Coal Basin, NW

Spain).

consistent with the compositional fractionation effects

observed in the solid residues.

Pores of various sizes were observed by optical

microscopy in the solid residues (Fig. 5). They begin to

appear for the temperature equal to 330 8C and increase in

size for the temperature 400 8C. So, the development of

vacuoles is weak at 330 8C and very intense from 400 8C,

indicating slow gas generation and expulsion at the

beginning of the heating process, and very rapid towards

the end.

3.2. Vitrinite reflectance and maturity

According to the vitrinite reflectance data (0.78%; [8])

the high volatile bituminous raw coal (Fig. 5; Table 1) is in a

mature stage of the oil window.

On the other hand, the mean random vitrinite reflectance

measurements in solid residues (Figs. 3A, B, and 5; Table 1)

range from 1.18 to 2.98 (%Rr), and coal rank varies from

high volatile bituminous to anthracite [37]. This trend

corresponds to a maturity of later oil to dry gas window.

At 400 8C, the solid residues show an increase in the

development of vacuoles due to volatile loss (Figs. 4C, D,

and 5). For the solid residues, calculated volatile matter from

vitrinite reflectance histograms [38,39] show very-low

values in agreement with the coal rank.

The artificial evolution of H, C, and O composition is

depicted on a van Krevelen diagram (Fig. 5), and it exhibits a

Table 1

Petrographic data of the solid residues from one coal sample from Pumarabule m

T (8C) Time (h) Vitrinite (%) Liptinite (%) Inertinite (%) Mineral matter

330 24 80.6 0.0 1.2 18.2

330 24 N.D. N.D. N.D. N.D.

330 120 89.0 0.0 1.4 9.6

330 720 82.4 0.0 1.4 16.2

360 24 88.6 0.4 2.4 8.6

360 120 90.6 0.0 1 8.4

360 720 86.8 0.0 0.6 12.6

400 24 86.8 0.0 2.4 10.8

400 120 91.0 0.0 1.0 8.0

400 720 91.2 0.0 0.6 8.2

N.D. = not determined.

similar trend to the natural evolution shown by Boudou [40],

and Landais and Gerard [24].

The vitrinite reflectance trend of the solid residues with

respect to temperature and time (Fig. 3A and B) of artificial

maturation can be described by an exponential curve.

The trend of observed vitrinite reflectance for the solid

residues after the artificial maturation can be described by an

exponential curve of smooth slope respect to temperature

and time (Fig. 3A and B). These curves do not show a strong

slope for the interval of 300 to 400 8C that others authors

(e.g., [41,25]) have described for humic coals.

The vitrinite reflectance of the solid residues increases

slowly from 1.17% Rr (24 h) to 1.80% Rr (720 h) at 330 8C,

from 1.51% Rr (24 h) to 2.97% Rr (720 h) at 360 8C, and

from 2.23% Rr (24 h) to 2.98% Rr (720 h) at 400 8C(Figs. 3A, B, and 5). Therefore, the temperature influence is

continuous whereas the time influence becomes smaller.

The increase in vitrinite reflectance is not as abrupt as

related in other studies (e.g., [41,25]). However, the

vitrinite reflectance rises with temperature is consistent

with other reported data [25]. The unique results of this

work could be explained by the pyrolysis method used.

Confined pyrolysis can simulate the natural thermal

evolution of the coals if it is considered the distribution

of the elemental composition including the H2O and CO2

formation (Fig. 5).

%Rr values from solid residues are higher than for the

original coal. Taking into account data reported by Piedad-

Sanchez et al. [7], on coal from the Pumarabule mine in the

ine (Central Asturian Coal Basin, Spain)

(%) Vitrinite (% mmf) Liptinite (% mmf) Inertinite (% mmf) %Rr

98.5 0.0 1.5 1.18

N.D. N.D. N.D. 1.17

98.5 0.0 1.5 1.38

98.3 0.0 1.7 1.80

96.9 0.4 2.6 1.51

98.9 0.0 1.1 1.90

99.3 0.0 0.7 2.37

97.3 0.0 2.7 2.23

98.9 0.0 1.1 2.64

99.3 0.0 0.7 2.98

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 65

Fig. 4. Initial Hg porosity (A and B) and calculated volatile matter formation (C and D) after artificial maturation of one coal sample from Pumarabule mine

(Central Asturian Coal Basin, NW Spain).

north of the Central Asturian Coal Basin, %Rr from ‘‘Marıa

Luisa Pack’’ is equal to 0.78, very similar to primary

cracking onset (330 8C; [13,24,42]) from solid residues; for

the Figaredo mine towards the south of the Pumarabule mine

and in the center of the Central Asturian Coal Basin, %Rr

from ‘‘Marıa Luisa Pack’’ coals range to 1.18 to 1.82,

Fig. 5. Van Krevelen diagram (1993) for the solid residues after artificial maturatio

indicating a maturation equivalent to secondary cracking

(360 8C; [13,24,42]); and for the San Antonio mine towards

the south of the Central Asturian Coal Basin, %Rr from

‘‘Marıa Luisa Pack’’ coals range of 2.09–2.54 indicating a

high maturity similar to the solid residues at 400 8C, and

suggest mainly a gas generation potential [13,24].

n of one coal sample from Pumarabule mine (Central Asturian Coal Basin).

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7666

The experimental cracking of selected coal in a closed

system shows that %Rr is a useful tool for determining the

maturation evolution in the Asturian coals and suggests a

gas-prone organic matter [13,43,42].

Nevertheless the slight differences observed in the

confined pyrolysis data, the general H/C, O/C, and %Rr

trends are similar and mimic natural maturation [44–

46,12,42]. %Rr is identified as the best maturation parameter

for the Asturian coals.

3.3. Organic geochemistry

3.3.1. Chemical conventional analyses

Piedad-Sanchez et al. [8] reported the results of chemical

and Rock-Eval analyses for the raw coal. The raw coal

exhibits a variable but low ash (from 5 to 12.04%db) and

volatile matter (from 39.39 to 42.09%daf) content which is

maintained by the solid residues.

The H/C and O/C atomic ratios (Fig. 5), HI and OI indices

(Fig. 6A), and Tmax and %Rr (Fig. 6B) show the composition

and the evolution trend followed by the coal during the

pyrolysis process as well as the oil generation potential for

the original studied coals [47–49,8]. However, in agreement

to Sykes and Snowdon [50], HI and Tmax indicate of a gas-

and oil-prone to gas-prone (Fig. 6C) where the horizontal

dashed lines show the proposed HI limits for the kerogen

classification by Peters and Moldowan [51]. Thus, the solid

residues from pyrolysis point out a similar trend to the

natural evolution of the Type III kerogen reported by

Fig. 6. Rock-Eval data graphics for the original coal samples from Pumarabule min

(C) HI vs. Tmax; (D) S2 vs. S1 peaks (modified from [7,8]).

Boudou [40], and Landais and Gerard [24], e.g., the

successive losses of oxygen and hydrogen and a quasi linear

increase of Tmax. Hence, the organic composition exhibits a

similar trend with an evolution from oil window to gas

window.

After Isaksen et al. [52], Killops et al. [53], Copard et al.

[54] and the data reported by Piedad-Sanchez et al. [8], HI

and Tmax data would suggest minimal oil generation

potential probably due to the influence of the resinitic

components and a low CO2 loss from the coals [8].

Previously data reported (e.g. [13,24,25,46]) indicate that

the confined pyrolysis plot fitted the natural trend. Thus, the

results obtained for the vitrinite reflectance after artificial

maturation could corroborate a suggested oil to gas –

generation potential as suggested by other traditional

parameters for the natural evolution of the original coal

from Pumarabule mine.

Values obtained for the S1 and S2 parameters (Fig. 6D)

show that the selected coal belongs to a group of lower rank

as other samples from Pumarabule mine [8]. According to

the data described by Sykes and Snowdon [50], the relatively

low S1 and high S2 values obtained from the original coal of

Pumarabule mine would suggest that it maintains its

petroleum potential because of low thermal transformation.

3.3.2. Molecular analyses

The raw coal is characterized by very-low extraction

yields [8], whilst the solid residues after artificial maturation

exhibit low- to middle extraction yields (Tables 2 and 3).

e (Central Asturian Coal Basin, NW Spain): (A) HI vs. OI; (B) Tmax vs. %Rr;

N.

Pied

ad

-San

chez

eta

l./J.A

na

l.A

pp

l.P

yrolysis

74

(20

05

)6

1–

76

67

Table 2

Molecular data of two original selected coals and of one selected coal after the artificial maturation from Pumarabule mine (Central Asturian Coal Basin, Spain)

Caudal-Nalon and La Justa-

Aramil units (Pumarabule

mine)

Sample (days, temperature (8C), pressure (bar))

Marıa Luisa

(Capa Burro)a

Generalas

(Capa Floja)a

1

(1, 330, 700)

3

(1, 330, 700)

7

(5, 330, 700)

20

(30, 330, 700)

4

(1, 360, 700)

8

(5, 360, 700)

2

(30, 360, 700)

5

(1, 400, 700)

9

(5, 400, 700)

Extraction yield

(mg/g)

6.46 3.46 Extraction yield

(mg/g)

62.41 53.84 66.06 58.06 77.47 48.98 9.69 33.47 3.91

% aliphatics 6.90 8.17 % aliphatics 6.32 5.52 5.89 10.29 8.42 10.91 14.09 6.78 1.78

% aromatics 18.39 23.50 % aromatics 18.02 16.09 17.46 21.44 16.80 20.49 42.61 24.87 53.25

% polars 74.71 68.33 % polars 75.66 78.39 76.66 68.27 74.79 68.60 43.30 68.34 44.97

CPI 1.31 1.05 CPI 1.12 1.12 1.09 1.07 1.09 1.09 1.12 1.13 N.D.

Pr/C17 3.91 1.92 Pr/C17 1.37 1.71 0.86 0.40 0.59 0.29 0.09 0.07 N.D.

Ph/C18 0.45 0.40 Ph/C18 0.25 0.27 0.18 0.13 0.15 0.11 0.04 0.04 N.D.

Pr/Ph 8.28 5.44 Pr/Ph 5.68 6.84 4.94 3.29 4.30 3.02 2.59 2.46 N.D.

A (%) 42.89 45.38 A (%) 37.44 35.23 39.48 41.10 46.19 52.77 47.54 65.24 N.D.

B (%) 38.05 31.30 B (%) 34.84 34.33 33.86 33.75 32.49 31.55 34.85 26.77 N.D.

C (%) 19.06 23.32 C (%) 27.72 30.44 26.67 25.14 21.32 15.69 17.61 7.99 N.D.

Rdit 1.65 1.12 R dit 1.19 1.29 0.72 1.65 0.90 1.72 0.95 1.11 N.D.

RC31 0.59 0.59 RC31 0.56 0.55 0.56 0.57 0.56 0.45 0.54 0.51 N.D.

RC32 0.59 0.59 RC32 0.55 0.54 0.56 0.53 0.58 0.40 0.54 0.53 N.D.

Ho/St 10.91 36.27 Ho/St 9.97 9.27 14.80 2.95 13.88 56.19 9.80 N.D. N.D.

%C27 steranes 16.05 17.97 %C27 steranes 13.62 13.24 21.93 34.57 34.72 0.00 17.82 N.D. N.D.

%C28 steranes 35.40 30.10 %C28 steranes 41.44 41.47 37.30 27.14 29.93 35.69 30.60 N.D. N.D.

%C29 steranes 48.55 51.93 %C29 steranes 44.93 45.29 40.77 38.29 35.35 64.31 51.58 N.D. N.D.

R1 0.42 0.33 R1 0.42 0.41 0.45 0.56 0.43 0.00 0.43 N.D. N.D.

R2 0.38 0.34 R2 0.38 0.36 0.41 0.31 0.40 0.00 0.39 N.D. N.D.

R* 0.37 0.36 R* 0.38 0.36 0.44 0.44 0.42 0.36 0.43 N.D. N.D.

MPI-1 0.66 0.60 MPI-1 0.61 0.62 0.65 0.89 0.65 0.89 1.19 0.85 0.88

%Rr of the coal 0.78 0.82 %Rr of the coal 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78

%Rc (from [71]) 0.77 0.77 1.91 1.76 1.91 1.76 1.58 1.79 1.77

%Rr of the solid residues 1.18 1.17 1.38 1.80 1.51 1.90 2.37 2.23 2.64

Nomenclature in Table 3.a Pack (coal seam).

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7668

Fig. 7. Total extract (%) and %Rr vs. time (A, B, and C) and %Rr (D, E, and F) for the solid residues after artificial maturation of one coal sample from

Pumarabule mine (Central Asturian Coal Basin, NW Spain).

Table 3

Peak assignments and nomenclature of biomarker data

Diterpanes (m/z = 123) Hopanes (m/z = 191) Steranes (m/z = 217) Aromatic (m/z = 178 and 192)

Labdane 17b (H) 22,29,30-trisnorhopane (C27) 14a,17a-Cholestane (20S) (C27) Phenantrene

19-Norisopimarane 17a (H) 21b (H)-norhopane (C29) 14b,17b-Cholestane (20R) (C27) 3-Methyl phenantrene

Ent-Beyerane 17a (H) 21b (H)-hopane (C30) 14b,17b-Cholestane (20S) (C27) 2-Methyl phenantrene

iso-Pimarane 22S 17a (H) 21b (H)-homohopane (C31) 14a,17a-Cholestane (20R) (C27) 9-Methyl phenantrene

16b-Phyllocladane 22R 17a (H) 21b (H)-homohopane (C31) 24-Methyl-14a,17a-cholestane (20S) (C28) 1-Methyl phenantrene

16a-Kaurane 22R 17a (H) 21b (H)-bishomohopane (C32) 24-Methyl-14b,17b-cholestane (20R) (C28)

16a-Phyllocladane 22S 17a (H) 21b (H)-bishomohopane (C32) 24-Methyl-14b,17b-cholestane (20S) (C28)

24-Methyl-14a,17a-cholestane (20R) (C28)

24-Ethyl-14a-cholestane (20S) (C29)

24-Ethyl-14b,17b-cholestane (20R) (C29)

24-Ethyl-14b,17b-cholestane (20S) (C29)

24-Ethyl-14a,17b-cholestane (20R) (C29)

N.D. = not determined. CPI = carbon preference index = [(C25 + C27 + C29 + C31 + C33)/(C24 + C26 + C28 + C30 + C32)] + [(C25 + C27 + C29 + C31 + C33)/

(C26 + C28 + C30 + C32 + C34)]. Pr = pristane; Ph = phytane; %C27 = (C27 � 100)/(C27 + C28 + C29); %C28 = (C28 � 100)/(C27 + C28 + C29);

%C29 = (C29 � 100)/(C27 + C28 + C29). A (%) = {S(C17:C19)}/{S(C17:C34)} ratio � 100; B (%) = {S(C20:C23)}/{S(C17:C34)} ratio � 100; C

(%) = {S(C24:C34)}/{S(C17:C34)} ratio � 100. Rdit = (19-norisopimarane + iso-pimarane + 16a-kaurane)/(ent-beyerane + 16b-phyllocladane + 16a-phyllo-

cladane). RC31 = [22S 17a (H) 21b (H)-homohopane (C31)]/{[22S 17a (H) 21b (H)-homohopane (C31)] + [22R 17a (H) 21b (H)-homohopane (C31)]}.

RC32 = [22R 17a (H) 21b (H)-bishomohopane (C32)]/{[22R 17a (H) 21b (H)-bishomohopane (C32)] + [22S 17a (H) 21b (H)-bishomohopane (C32)]}. Ho/

St = hopane/sterane ratio. R1 = [24-ethyl-14a-cholestane (20S) (C29)]/{[24-ethyl-14a-cholestane (20S) (C29)] + [24-ethyl-14a,17b-cholestane (20R) (C29)]}.

R2 = {[24-ethyl-14a-cholestane (20S) (C29)] + [24-ethyl-14b,17b-cholestane (20S) (C29)]}/{[24-ethyl-14a-cholestane (20S) (C29)] + [24-ethyl-14b,17b-

cholestane (20R) (C29)] + [24-ethyl-14b,17b-cholestane (20S) (C29)] + [24-ethyl-14a,17b-cholestane (20R) (C29)]}. R* = [14a,17a-cholestane (20S)

(C27)] + [14b,17b-cholestane (20S) (C27)] + [24-methyl-14a,17a-cholestane (20S) (C28)] + [24-methyl-14b,17b-cholestane (20S) (C28)] + [24-ethyl-14a-

cholestane (20S)-C 29] + [24-ethyl-14b,17b-cholestane (20S) (C29)]/{[14a,17a-cholestane (20S) (C27)] + [14b,17b-cholestane (20S) (C27)] + [24-methyl-

14a,17a-cholestane (20S) (C28)] + [24-methyl-14b,17b-cholestane (20S) (C28)] + [24-ethyl-14a-cholestane (20S) (C29)] + [24-ethyl-14b,17b-cholestane

(20S) (C29)]} + {[14b,17b-cholestane (20R) (C27)] + [14a,17a-cholestane (20R) (C27)] + [24-methyl-14b,17b-cholestane (20R) (C28)] + [24-methyl-

14a,17a-cholestane (20R)-Qs] + [24-ethyl-14b,17b-cholestane (20R) (C29)] + [24-ethyl-14a,17b-cholestane (20R) (C29)]}. MPI-1 = 1.5 � (3-methyl-phe-

nanthrene + 2-methyl-phenanthrene)/(phenanthrene + 9-methyl-phenanthrene + 1-methyl-phenanthrene). %Rr = measured vitrinite reflectance.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 69

With increasing maturation (time and temperature) the

solid residues show a decrease in aliphatic and polar content,

and an increase in the aromatics (Figs. 7A–C and 8C–E).

This trend is also observed on the measured %Rr (Figs. 7D–F

and 8A–B).

The total extract yields of the solid residues for 24 h show

an initial high polar and aromatic content at 330 8C; then a

slight decrease at 360 8C of the polar and aromatic content,

followed towards end at 400 8C, of a light increase in

aromatics and a slight diminution of the polars; for 120 h, the

highest extraction of the aromatics occurs at 330 8C, then a

high decrease of polars and a light augmentation of aromatics

at 360 8C, and at last, a strong increase of aromatics and a

diminution of polars at 400 8C; finally, for 720 h, a high value

of the aromatic and polar content at 330 8C at the beginning,

then an abrupt diminution of polars and a strong increase of

aromatics at 360 8C, and this trend continues at 400 8C(Fig. 8C–E). The trend suggests temperature has a great

influence that time [12] on the coal sample during the artificial

maturation, suggesting the high potential of hydrocarbon

generation in the Asturian coals. The high original vitrinite

content (Fig. 2; [8]) leads to low quantity of extraction yields.

Vitrinite-rich coals mainly generate gaseous hydrocarbons

during the thermal evolution [49,39].

Fig. 8. Total extract (%) vs. %Rr (A), %Rr vs. temperature (B), and total extract (%)

of one coal sample from Pumarabule mine (Central Asturian Coal Basin, NW S

The extracts of the solid residues show two types of

transformation mechanisms (Table 2): a rapid decomposi-

tion at 330 8C with high gas and liquid generation, and rapid

condensation predominates at 400 8C leading to an increase

in the aromaticity [55,56,39,25]. The increase in vitrinite

reflectance of the solid residues with increase of the

temperature and time reflects the rapid decomposition and

condensation (Figs. 7D–F and 8C–E).

In the Central Asturian Coal Basin, and in others basins

[41,57,25,8], the polar percentage is higher than aromatic

and aliphatic percentages in the less mature coals. The solid

residues show a slowly decrease in the aliphatic content, a

decrease in polars and an increase in aromatics with the

increase of the maturation. Therefore, the influence of

temperature and time provokes a condensation mechanism,

and an increase in the vitrinite reflectance. Taking into

account the original composition of the studied coal, the

solid residues would indicate mainly a strong potential of

gaseous hydrocarbon generation.

3.3.3. Aliphatics

The m/z 57 chromatograms of the raw coal is unimodal

(Fig. 9) with maximum peaks at nC19.Values for the A, B, C,

ratio (Table 2) show that C17 to C18 n-alkanes represent 43%

vs. temperature (C, D, and E) for the solid residues after artificial maturation

pain).

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7670

Fig. 9. Examples of the typical distributions of the n-alkanes (m/z 57) for the original coal sample and the solid residues after artificial maturation at different

temperatures of one coal sample from Pumarabule mine (Central Asturian Coal Basin, NW Spain). Peak assignments in Table 3.

of all alkanes, C19 to C23 n-alkanes 38%, and C24 to C31 n-

alkanes 19% [8]. On the other hand, the m/z 57

chromatograms of the solid residues after artificial matura-

tion are also unimodal (Fig. 9) with maximum peaks

between nC14 and nC22. A, B, C, ratios (Table 2) show that

C17 to C18 n-alkanes represent 35–65% of all alkanes, C19 to

C23 n-alkanes 27–35%, and C24 to C31 n-alkanes 8–30%. In

general, C17 to C18 n-alkanes increase with the temperature

more that with the time, while C24 to C31 n-alkanes decrease

in the solid residues obtained after confined pyrolysis.

CPI is equal to 1.31 (Table 2), Pr/Ph ratio to 8.28, Pr/nC17

ratio to 3.91, and Ph/nC18 ratio to 0.45 in the original coal

[8]. On the other hand, CPI ranges from 1.07 to 1.13

(Table 2), Pr/Ph ratio from 2.46 to 6.84, Pr/nC17 ratio from

0.07 to 1.71, and Ph/nC18 ratio from 0.04 to 0.27 in the solid

residues. In general, Pr/Ph, Pr/nC17, and Ph/nC18 ratios

exhibit low values with the temperature and time increases,

while CPI shows a relatively stability for the solid residues.

The low contribution of the C25 n-alkanes reflects a

thermal effect [58–61,8] in the original Pumarabule coal.

This effect is also observed in the m/z 57 chromatograms of

the solid residues and would suggest that the maceral

composition did not affect the timing of hydrocarbon

generation onset of the raw coal since the thermal fingerprint

is maintained during the confined pyrolysis despite the

different proportions of macerals (collotelinite, collodetri-

nite, sporinite, resinite, etc.) sealed in each gold cell.

CPI values for original [8] and matured coals show a

similar maturity for each. CPI values are lower for pyrolysed

coals than in original coals revealing the disappearance of

the initial predominance of odd n-alkanes in the C24–C34

range [62,24]. For coals from the Central Asturian Coal

Basin [8] and Ruhr Basin (this last case was described by

Littke et al. [60,61]), Pr/Ph ratio presents a maximum at %Rr

equal to 0.9, then decreases for the high %Rr values

(Fig. 10A). High Pr/Ph ratio supports the land-derived origin

of the coal sample, and the thermal effect first increases, then

decreases the value of this ratio [8].

From diterpane groups (m/z 123) found in the original coal

and the solid residues (Fig. 11), Rdit ratio was calculated

(Rdit = 19-norisopimarane + iso-pimarane + 16a-kaurane)/

(ent-beyerane + 16b-phyllocladane + 16a-phyllocladane)

(Table 2) according to Fleck [63]. Raw coal exhibits values of

Rdit equal to 1.65, while the solid residues show values

between 0.72 and 1.72. The abundance of diterpanes

decreases with the increase of temperature and no diterpanes

were detected after pyrolysis at 400 8C. Rdit values in the solid

residues generally decrease with increasing maturation. High

Rdit values probably arise and reflect input from several

sources of terrestrial organic matter [63,35]. The slight

decrease of Rdit reflects the maturation behaviour of this

parameter [8].

The hopanes (m/z 191) show a similar distribution for the

raw and matured coals [8] although peak abundance decreases

with the increase of temperature (Fig. 12). Ho/St ratio of the

original coal is equal to 10.91, and from 3 to 56 in the solid

residues. In general for the solid residues, Ho/St ratio

increases with increasing maturation, and then decreases.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 71

Fig. 10. (A) Pr/Ph ratio, (B) Ho/St ratio, and (C) total extract yield vs. % measured Rr for the original coals and the solid residues after artificial maturation for

one coal sample from Pumarabule mine (Central Asturian Coal Basin, NW Spain).

The hopane content indicates the bacterial presence at the

swamp [64] and an oxic-type paleoenvironment at the coals

[8]. The hopane/sterane ratio would confirm the bacterial

presence at all samples [65,66]. The increasing maturity of

the solid residues reflects the thermal evolution at the

original coal revealing a strong influence of the previous

thermal overprint [67]. The hopane/sterane ratio for the solid

residues peaks at a %Rr = 0.8 (Fig. 10B) and then, decreases

indicating the influence of artificial maturation. This

transformation is also indicated by the hopane/sterane ratios

in the original coals of the basin (Fig. 10B).

Hopane isomere ratios RC31 and RC32 already reached

equilibrium (0.6) from original sample at 0.78% Rr. After

Fig. 11. Examples of the typical distributions of the diterpanes (m/z 123) for the ori

temperatures for one coal sample from Pumarabule mine (Central Asturian Coal

Peters and Moldowan [51], this equilibrium is reached at

0.6% Rr. These ratio cannot be used for calibration.

The C27, C28, C29 sterane (m/z 217) percentages and R1,

R2 and R* ratios were also calculated for the original and

pyrolysed coals [8] (Table 2). Original coal presents a

majority of C29 (49%) sterane, then C28 (35%) (Fig. 13),

followed by C27 (16%) steranes. The solid residue values

range for C29 from 35 to 64%, for C28 from 27 to 42%, and

for C27 from 0 to 35% (Fig. 13). In general the solid

residues, show a decrease in C29 and C28 percentages, and

an increase in C27 steranes with increasing maturation,

temperature, and time. No steranes were detected after

400 8C pyrolysis.

ginal coal sample and the solid residues after artificial maturation at different

Basin, NW Spain). Peak assignments in Table 3.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7672

Fig. 12. Examples of the typical distributions of the hopanes (m/z 191) for the original coal sample and the solid residues after artificial maturation at different

temperatures for one coal sample from Pumarabule mine (Central Asturian Coal Basin, NW Spain). Peak assignments in Table 3.

According to Huang and Meinschein [68,69], the relative

proportion of C27–C28–C29 steranes suggests a thermal

mature original coal [8]. This fingerprint is maintained

during the artificial maturation process. Particularly, for the

solid residues, the sterane percentages suggest a molecular

Fig. 13. Examples of the typical distributions of the steranes (m/z 217) for the orig

temperatures for one coal sample from Pumarabule mine (Central Asturian Coal

recombination with increasing maturation. Taking into

account maturity data reported by Elie et al. [67], the sterane

distribution is relatively more unstable provoking a

maximum recombination until it disappears at high

temperatures.

inal coal sample and the solid residues after artificial maturation at different

Basin, NW Spain). Peak assignments in Table 3.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 73

Sterane isomere ratio R1 and R2 vary from 0.42 for

original sample at 0.78% Rr to 0.56 at 1.8% Rr. After Peters

and Moldowan [51], this equilibrium is reached at 0.6 for

0.75% Rr. These ratio cannot be used for calibration.

3.3.4. Aromatics

Phenanthrene, methyl-phenanthrenes and di-methyl-

phenanthrenes were in the raw and matured coals

(Fig. 14). The alkyl-phenanthrenes in the solid residues

indicates the condensation of the aromatic rings in

agreement with increasing maturity indicated by the vitrinite

reflectance values.

The methyl-phenanthrenes index (MPI-1; [70]) was

calculated (Table 2). A gas window for the original coal, and

an oil to gas window for the solid residues [71,8]. For the

solid residues, the calculated vitrinite reflectance (Table 2)

was determined by using the relationship proposed by Radke

and Welte [71]:

%Rc ¼ 0:60ðMPI-1Þ þ 0:40 for Rr < 1:35:

%Rc ¼ �0:60ðMPI-1Þ þ 2:30 for Rr > 1:35:

We calculated also the %Rc (Rc = 0.63(MPI-1) + 0.42)

(Fig. 15A). Rc values indicate for 24 h an increase at 330 and

360 8C, and a general decrease at 400 8C; for 120 h, an

increase at 330 8C, then a general decrease at 360 and

400 8C; and finally for 720 h, an increase at 330 8C, and then

a diminution at 360 8C (Table 2, and Fig. 15A). Rc values are

slightly smaller than Rr measured in the solid residues

(Table 2, and Fig. 15B).

Fig. 14. Examples of the typical aromatic (SIM of m/z 178 and 192) distributions f

different temperatures for one coal sample from Pumarabule mine (Central Astu

MPI-1 values for original coal indicate a gas and oil

window maturity which is consistent with others maturity

estimates [8]. The MPI-1 of solid residues is clearly affected

by maturation (Fig. 15B), and these values do not suggest an

influence by the mineral catalysis because the samples have

the same composition with very low mineral matter content.

%Rc values show the influence of temperature and time

increases (Fig. 15A) but also, these values are affected by the

processes of condensation during the coalification mechan-

isms. Thus, for the solid residues, %Rc values are relatively

low with respect to the measured Rr during the primary

cracking (330 8C). The low %Rc values are similar to the

measured %Rr during the secondary cracking (360 8C), but

much lower than the %Rr during the highest 400 8Ctemperature used (Fig. 15B). This trend could be explained

by the complex polycondensation reactions in the aromatics

and various functional groups that occur during maturation

[72,43,42]. Therefore, MPI-1 and %Rc may help to establish

the maturation level of in the Asturian coals.

Naphthalene, methyl-naphthalenes, di- and trimethyl-

naphthalenes, methyl-dibenzofuranes, fluoranthene and

pyrene, benzofluoranthene, benzo[e]pyrene and benzo[a]-

pyrene were also detected in ‘‘Fullscan’’ and SIM [8]. Low

quantities of the fluoranthene and pyrene, benzofluor-

anthene, benzo[e]pyrene and benzo[a]pyrene in the source

coal suggest a humid climate during the deposition of

original coal [73]. The relative abundance of these

polycyclic aromatic hydrocarbons in the solid residues

reflects their high thermal stability.

or the original coal sample and the solid residues after artificial maturation at

rian Coal Basin, NW Spain). Peak assignments in Table 3.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7674

Fig. 15. (A) % calculated Rr vs. MPI-1, and (B) % measured Rr vs. MPI-1 for the solid residues after artificial maturation for one coal sample from Pumarabule

mine (Central Asturian Coal Basin, NW Spain).

3.3.5. Kinetic interpretation

A comparison of the results of bulk and molecular

geochemical parameters (Pr/Ph and Ho/St ratios) during

natural and artificial maturation clearly shows the low

maturity of extractable hydrocarbons (Fig. 10A and B). The

artificial maturation experiments performed on the coals

help define the thermal evolution of the basin described in

greater detail by Piedad-Sanchez et al. [7]. Fig. 10C shows a

maximum extraction yields at %Rr = 1.5. The Pr/Ph and Ho/

St parameters decrease throughout the oil window. This is

likely due to secondary cracking of the free hydrocarbons

(Fig. 8C–E) which are occurring extensively at %Rr = 1.5.

Therefore, the %Rr parameter increases with increasing

temperature (Fig. 8C–E), while the time help to accelerate

the chemical changes of the extract composition, and

therefore, of the maturation reflected in the %Rr. This could

involve the thermal transformation of the polars compounds

and the aromatic hydrocarbon formation. These compounds

are sensitive to time because its secondary transformation

begins at 330 8C (Fig. 7A–C). This transformation does not

follow the %Rr values, for example, at 720 h, the

%Rr = 1.5, but the transformation has not started. Thus,

the transformation and aromatic hydrocarbon generation

are favoured by the increase of the time together with the

temperature.

For the solid residues obtained in this work, it is clear that

the original maceral coal composition is thermally

transformed during the artificial maturation [74]. The

measured Rr values for the extracted solid residues are

significantly higher than their Rc values calculated MPI-1

ratios (Table 2, Fig. 15A and B) suggesting that the

maturation conditions used induce a smoothing linear

influence on the chemical transformations [72,43,42]. This

chemical transformation could be related to a combination

of substitution processes and condensation of aromatic rings

[55,56,17,43,24,39,25]. Therefore, the expulsion phenom-

ena in the artificial maturation will influence on the organic

reactions that occur during maturation, and would be

associated with the porosity increase observed in the solid

residues with increasing temperature (Fig. 5).

4. Conclusions

In this work, confined pyrolysis allowed to simulate the

natural evolution or maturation of one Asturian high volatile

bituminous coal. This experiment helped to verify the

physical and chemical changes in the raw coal with

increasing maturation. The most obvious of these changes

were the increases in porosity, vitrinite reflectance and

aromaticity.

Previous petrographic and geochemical results will

permit to compare, to simulate and to estimate the natural

coal maturation and the gas production of the Central

Asturian Coal Basin with a kinetic model called META-

GAZ-1D in the part II of this paper [75].

Acknowledgements

The authors express their gratitude to HUNOSA Co.,

especially to J.A. de Saenz de Santamarıa for the data and

coal samples supplied. The authors are also indebted to

INCAR-CSIC (Spain) and G2R-Universite de Nancy

(France) for the help in the analyses. Piedad-Sanchez

gratefully acknowledges the help of CONACYT (Consejo

Nacional de Ciencia y Tecnologıa, Mexico) for the

scholarship support.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–76 75

References

[1] M. Gutierrez-Claverol, C. Luque-Cabal, in: C. Aramburu, F. Bastida

(Eds.), Geologıa de Asturias, Ediciones TREA, Principado de Astur-

ias, Spain, 1995, pp. 187–202.

[2] P. Fuente-Alonso, J.A. Saenz de Santa Marıa Benedet, La tectonica y

microtectonica de la Cuenca Carbonıfera Central de Asturias, Vol.

Homenaje a J. Truyols, Universidad de Oviedo, Trabajos de Geologıa

21, 1999, pp. 121–140.

[3] J.R. Colmenero, J.G. Prado, Int. J. Coal Geol. 23 (1993) 215–229.

[4] O.E. Alonso, C. Brime, Clays Clay Miner. 38 (1990) 265–276.

[5] N. Piedad-Sanchez, I. Suarez-Ruiz, L. Martınez, J. Duplay, L. Amir, P.

Faure, A. Izart, in: Proceedings of the Eighth Latin-American

Congress on Organic Geochemistry, Cartagena de Indias, Colombia,

2002 , pp. 38–40(Abstracts).

[6] N. Piedad-Sanchez, I. Suarez-Ruiz, L. Martınez, P. Faure, M. Elie,

Petrographic and Geochemical Observations About the Gas Formation

into the Asturias Basin, Resumes, 19eme Reunion des Sciences de la

Terre, Planetologie et Geodynamique, Faculte des Sciences et des

Techniques, Universite de Nantes, France, 2002, 19 pp.

[7] N. Piedad-Sanchez, A. Izart, L. Martinez, I. Suarez-Ruiz, M. Elie, Int.

J. Coal Geol. 58 (2004) 205–229.

[8] N. Piedad-Sanchez, I. Suarez-Ruiz, L. Martinez, A. Izart, M. Elie, D.

Keravis, Int. J. Coal Geol. 57 (2004) 211–242.

[9] E. Stach, M.T. Mackowsky, M. Teichmuller, G.F. Taylor, G. Chandra,

R. Teichmuller, Stach’s Textbook of Coal Petrology, Gebruder

Borntraeger, Berlin, 1982.

[10] K.E. Peters, B.G. Rohrback, I.R. Kaplan, Am. Assoc. Petrol. Geol.

Bull. 65 (1981) 688–705.

[11] B.G. Rohrback, K.E. Peters, I.R. Kaplan, Am. Assoc. Petrol. Geol.

Bull. 68 (1984) 961–970.

[12] W.L. Huang, Org. Geochem. 24 (1996) 233–241.

[13] M. Monthioux, P. Landais, J.C. Monin, Org. Geochem. 8 (1985) 275–

292.

[14] P. Landais, M. Monthioux, Fuel Process. Tech. 20 (1988) 123–132.

[15] P. Landais, R. Michels, B. Poty, M. Monthioux, J. Anal. Appl. Pyrol.

16 (1989) 103–115.

[16] P. Landais, R. Michels, M. Elie, in: A.G. Douglas, N. Telnæ, N. Hydro,

K. Øygard, G.V.G. Statoil (Eds.), Advances in Organic Geochemistry

1993, Org. Geochem. 22 (1994) 617–630.

[17] Z. Benkhedda, P. Landais, J. Kister, J.M. Dereppe, M. Monthioux,

Energy Fuels 6 (1992) 166–172.

[18] L. Gerard, M. Elie, P. Landais, J. Anal. Appl. Pyrol. 29 (1994) 137–

152.

[19] L. Mansuy, P. Landais, Energy Fuels 9 (1995) 809–821.

[20] L. Mansuy, P. Landais, O. Ruau, Energy Fuels 9 (1995) 691–703.

[21] R. Michels, P. Landais, B.E. Torkelson, R.P. Philp, Geochim. Cos-

mochim. Acta 59 (1995) 1589–1604.

[22] R. Michels, E. Langlois, O. Ruau, L. Mansuy, M. Elie, P. Landais,

Energy Fuels 10 (1996) 39–48.

[23] R. Michels, N. Enjelvin-Raoult, M. Elie, L. Mansuy, P. Faure, J.L.

Oudin, Mar. Petrol. Geol. 19 (2002) 589–599.

[24] P. Landais, L. Gerard, Int. J. Coal Geol. 30 (1996) 285–301.

[25] Z. Han, Q. Yang, Z. Pang, Int. J. Coal Geol. 46 (2001) 133–143.

[26] R. Michels, P. Landais, R.P. Philp, B.E. Torkelson, Energy Fuels 8

(1994) 741–754.

[27] UNE 32300, Hulla y antracita, Petrografıa, Preparacion de muestras de

carbon para analisis microscopico, AENOR, 1995, 13 pp.

[28] International Organization for Standardization, ISO 7404-2, Methods

for the petrographic analysis of bituminous coal and anthracite. Part 2.

Preparation of coal samples, International Organization for Standar-

dization, Switzerland, 1985, 8 pp.

[29] International Organization for Standardization, ISO 7404-3, Methods

for the petrographic analysis of bituminous coal and anthracite. Part 3.

Method of determining maceral group composition, International

Organization for Standardization, Switzerland, 1994, 6 pp.

[30] International Organization for Standardization, ISO 7404-5,

Methods for the petrographic analysis of bituminous coal and anthra-

cite. Part 5. Method of determining microscopically the reflectance

vitrinite, International Organization for Standardization, Switzerland,

1994, 12 pp.

[31] J. Espitalie, G. Deroo, F. Marquis, La pyrolyse Rock-Eval et ses

applications. Premiere Partie. Oil & Gas Science and Technology-

Revue de l’Institut Francais du Petrole 40 (1985) 563–579.

[32] J. Espitalie, G. Deroo, F. Marquis, La pyrolyse Rock-Eval et ses

applications. Deuxieme Partie. Oil & Gas Science and Technology-

Revue de l’Institut Francais du Petrole 40 (1985) 755–784.

[33] J. Espitalie, G. Deroo, F. Marquis, La pyrolyse Rock-Eval et ses

applications. Troisieme Partie. Oil & Gas Science and Technology-

Revue de l’Institut Francais du Petrole 41 (1985) 73–89.

[34] M. Radke, Mar. Petrol. Geol. 5 (1985) 224–236.

[35] S. Fleck, R. Michels, A. Izart, M. Elie, P. Landais, Int. J. Coal Geol. 48

(2001) 65–88.

[36] J.G. Stainforth, J.E.A. Reinders, in: B. Durand, F. Behar (Eds.),

Advances in Organic Geochemistry 1989, Org. Geochem. 16

(1990) 61–74.

[37] ASTM (American Society for Testing and Materials), Standard clas-

sification of coals by ranks D388, in: 2001 Annual Book of ASTM

Standards, Section 5: Petroleum Products, Lubricants and Fossil Fuels.

Gaseous Fuels, Coal and Coke, vol. 6, ASTM, Philadelphia, PA, 2001,

668 pp.

[38] M. Teichmuller, Coal and Coal-bearing Strata: Recent Advances, vol.

32, Geological Society, 1987, pp. 125–169 (Special Publication).

[39] G.H. Taylor, M. Teichmuller, A. Davis, C.F.K. Diessel, R. Littke, P.

Robert, in: Organic Petrology: A New Handbook Incorporating Some

Revised Parts of Stach’s Textbook of Coal Petrology with Contribu-

tions of Glick, D.C., Davis, A., Smyth, M., Swain, D.J., Vander-

broucke, M., Espitalie, J. Gebruder Borntraeger, Berlin, Sttugart,

1998, pp. 371–391.

[40] J.P. Boudou, Diagenese organique de sediments deltaiques (delta de la

Mahakam - Indondesie), Ph.D. These, Universite d’Orleans, Orleans,

1981.

[41] T.I. Eglinton, A.G. Douglas, S.J. Rowland, in: L. Mattavelli, L. Novelli

(Eds.), Advances in Organic Geochemistry. Part II. Analytical Geo-

chemistry, Org. Geochem. 13 (1987) 655–663.

[42] F. Behar, M. Vandenbroucke, Y. Tang, F. Marquis, J. Espitalie, Org.

Geochem. 26 (1997) 321–339.

[43] F. Behar, M. Vandenbroucke, S.C. Teermann, P.G. Hatcher, C.

Leblond, O. Lerat, Chem. Geol. 126 (1995) 247–260.

[44] S.C. Teerman, R.J. Huang, Org. Geochem. 17 (1991) 749–764.

[45] R. Michels, P. Landais, Fuel 73 (1994) 1691–1696.

[46] F. Behar, M.D. Lewan, F. Lorant, M. Vandenbroucke, Org. Geochem.

34 (2003) 575–600.

[47] B. Durand, J.C. Monin, in: B. Durand (Ed.), Kerogen: Insoluble

Organic Matter from Sedimentary Rocks, Institut Francais du Petrole,

Paris, France, 1980, pp. 113–142 (Editions Technip).

[48] M. Teichmuller, B. Durand, Int. J. Coal Geol. 2 (1983) 197–230.

[49] B.P. Tissot, D.H. Welte, Petroleum Formation and Occurrence. A New

Approach to Oil and Gas Exploration, 2nd ed., Springer-Verlag, New

York, 1992.

[50] R. Sykes, L.R. Snowdon, Org. Geochem. 33 (2002) 1441–1455.

[51] K.E. Peters, J.M. Moldowan, The Biomarker Guide. Interpreting

Molecular Fossils in Petroleum and Ancient Sediments, Prentice-Hall,

New Jersey, 1993, 363 pp.

[52] G.H. Isaksen, D.J. Curry, J.D. Yeakel, A.I. Jenssen, Org. Geochem. 29

(1998) 23–44.

[53] S.D. Killops, R.H. Funnell, R.P. Suggate, R. Sykes, K.E. Peters, C.

Walters, A.D. Woolhouse, R.J. Weston, J.P. Boudou, Org. Geochem.

29 (1998) 1–21.

[54] Y. Copard, J.R. Disnar, J.F. Becq-Giraudon, Int. J. Coal Geol. 49

(2000) 57–65.

[55] F. Derbyshire, A. Davis, R. Lin, Energy Fuels 3 (1989) 431–437.

N. Piedad-Sanchez et al. / J. Anal. Appl. Pyrolysis 74 (2005) 61–7676

[56] F. Derbyshire, Fuel 70 (1991) 153–161.

[57] J. Rullkotter, R. Marzi, in: L. Mattavelli, L. Novelli (Eds.), Advances

in Organic Geochemistry. Part II. Analytical Geochemistry, Org.

Geochem. 13 (1987) 639–645.

[58] J. Allan, A.G. Douglas, Geochim. Cosmochim. Acta 41 (1977) 1223–

1230.

[59] M. Radke, R.G. Schaefer, D. Leythaeuser, Geochim. Cosmochim.

Acta 44 (1980) 1787–1800.

[60] R. Littke, B. Horsfeld, D. Leythaeuser, Geologische Rundschau 78

(1989) 391–410.

[61] R. Littke, D. Leythaeuser, M. Radke, R.G. Schaefer, Org. Geochem.

16 (1989) 247–258.

[62] M. Monthioux, Maturations naturelle et artificielle d’une serie de

charbons homogenes, Thesis, Universite d’Orleans, Orleans, France,

1986, 331 pp.

[63] S. Fleck, Correlation entre geochimie organique, sedimentologie et

stratigraphie sequentielle pour la caracterisation des paleoenvironne-

ments de depot, Ph.D. Thesis, Universite Henri Poincare, Nancy,

France, 2001.

[64] G. Ourisson, P. Albrecht, J.R. Maxwell, R.E. Wheatley, Pure Appl.

Chem. 51 (1979) 709–729.

[65] C.J. Boreham, R.E. Summons, Z. Roksandic, L.M. Dowling, A.C.

Hutton, Org. Geochem. 21 (1994) 685–712.

[66] A. Bechtel, W. Gruber, R.F. Sachsenhofer, R. Gratzer, W. Puttmann,

Org. Geochem. 32 (2001) 1289–1310.

[67] M. Elie, P. Faure, R. Michels, P. Landais, L. Griffault, Energy Fuels 14

(2000) 854–861.

[68] W.Y. Huang, W.G. Meinschein, Geochim. Cosmochim. Acta 40

(1976) 323–330.

[69] W.Y. Huang, W.G. Meinschein, Geochim. Cosmochim. Acta 43

(1979) 739–745.

[70] M. Radke, H. Willsch, D. Leythaeuser, Geochim. Cosmochim. Acta 46

(1982) 1831–1848.

[71] M. Radke, D.H. Welte, in: M. Bjorøy, C. Albrecht, C. Cornford, K. De

Groot, G. Eglinton, E. Galimov, D. Leythaeuser, R. Pelet, J. Rullk-

oetter, G. Speers (Eds.), Advances in Organic Geochemistry 1981,

Wiley, New York, 1983, pp. 504–512.

[72] E. Adler, Wood Sci. Technol. 11 (1977) 69–218.

[73] C. Jiang, R. Alexander, R.I. Kagi, A.P. Murray, Org. Geochem. 29

(1998) 1721–1735.

[74] A. Wan Hasiah, in: H.I. Petersen (Ed.), Abstracts of the Society for

Organic Petrology (TSOP)/International Committee for Coal and

Organic Petrology (ICCP), Proceedings of the 53rd Meeting of the

International Committee for Coal and Organic Petrology, Copenha-

gen, Denmark, 2001, pp. 146–151.

[75] N. Piedad-Sanchez, L. Martınez, A. Izart, I. Suarez-Ruiz, M. Elie, C.

Menetrier, F. Lannuzel, Artificial maturation of a high volatile bitu-

minous coal from Asturias (NW Spain) in a confined pyrolysis system.

Part II. Gas production during pyrolysis an numerical simulation, J.

Anal. Appl. Pyrol. 74 (2005) 77–87.