Influence of rock particle size on the artificial thermal evolution of kerogen. A petrographic and geochemical study

Suárez‐Ruíz, Isabel; Martı́nez, Luis; Bertrand, Ph.; Salas, Javier González de Prado; Disnar, Jean-Robert

doi:10.1016/0166-5162(94)90004-3

Cited by 17 publications

(18 citation statements)

References 6 publications

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“…This sample is an oil-prone vitrinite (S 2 from Rock-Eval pyrolysis: 291 mg HC g À1 sample; oil yield from Gray-King pyrolysis: 27%) and it is characterised by the presence of thermally labile structures and lower values of T max and T DTGmax [15,16]. This coal was pyrolysed at different temperatures in an offline open-medium pyrolysis system (using Gray-King assay oven type) [6,7]. Grains of vitrinite (%1 mm size) were placed in an isothermal quartz reactor for 10 h, the temperature being increased 25 8C over a temperature range of 250-500 8C.…”

Section: Methodsmentioning

confidence: 99%

“…To achieve this, the TCV vitrinite, whose structure was strongly modified by the presence of terpene-type resin, was heated to different temperatures ranging from 250 to 500 8C, and the results concerning mass balance, characterisation of solid residues and the structural study of the generated oils were compared with those previously obtained for other vitrinites (non-perhydrous and perhydrous) subjected to the same thermal treatment [7,9]. Pyrolysis was performed in an open-medium system which proved earlier to be useful in the study of the evolution of oil shales (type II kerogen) and coals (type III kerogen) [6,7]. The absence of a flow of inert gas in this system allowed the retention, to some extent, of some of the compounds generated in conditions less drastic than those of confined pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, natural evolution can be considered as a peculiar kind of pyrolysis which normally occurs at low temperatures (<200 8C) over millions of years. For this reason, different pyrolysis experiments were used to obtain valuable information about the phenomena that occur during natural evolution [3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Chemical-structural changes during the thermal treatment of hydrogen-rich vitrinites caused by the presence of terpene-type resin

Iglesias

Cuesta

Laggoun‐Défarge

et al. 2006

Journal of Analytical and Applied Pyrolysis

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The vitrain from Teruel (North-Eastern Spain) is a good example of a vitrinite whose perhydrous character and anomalous properties are caused by the presence of terpene-type resin. The sample used in this work was isothermally pyrolysed in an open-medium system at temperatures ranging from 250 to 500 °C. A mass balance, a petrographic and geochemical characterisation of the pyrolysates and compositional and structural analyses (GC and NMR) of the generated oils were performed. The results confirm the association of huminite-resinous substances through covalent bonds and also point to the possible incorporation of aliphatic material via covalent oxygen bonds. The side-chains that serve as linkers between the phenolic subunits derived from the lignin contain more labile thermal bonds than those present in other vitrinites not affected by resin saturation. Consequently, this type of vitrinite undergoes a more intense degradation at lower temperatures than non-perhydrous and other hydrogen-rich vitrinites. The vitrinite network itself due to the incorporation of resin-like substances (cycloparaffinic in nature) may serve as a hydrogen donor, enhancing the hydrogenation processes during pyrolysis with respect to the polymerisation and recombination reactions. The higher ability of hydrogen to stabilise the free radicals formed during pyrolysis explains the higher conversion to liquids at lower temperatures than in the case of non-perhydrous vitrinites. At the same time, this ability limits the growth of the aromatic structures. The evolution of the vitrinite modified by the presence of terpene-type resin is, thus, retarded with respect to non-perhydrous vitrinites, although in both cases the trend followed is very close. In contrast the trend of this type of vitrinite differs considerably from that of perhydrous vitrinites which are affected by hydrocarbon impregnation. Only for the most severe treatments (450/500 °C) was some degree of structural uniformity observed in the solid residues

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemical-structural changes during the thermal treatment of hydrogen-rich vitrinites caused by the presence of terpene-type resin

Iglesias

Cuesta

Laggoun‐Défarge

et al. 2006

Journal of Analytical and Applied Pyrolysis

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“…Gray-King pyrolysis was performed in accordance with the modification of the standard procedure (ISO 502) described by Suárez-Ruiz et al [12]. Between 5 and 15 g of sample with a particle size of 1.0 mm was placed inside a quartz reactor, 2 cm in diameter and 25 cm long.…”

Section: Methodsmentioning

confidence: 99%

1D-NMR and 2D-NMR analysis of the thermal degradation products from vitrinites in relation to their natural hydrogen enrichment

Iglesias¹,

Cuesta²,

Laggoun‐Défarge³

et al. 2006

Journal of Analytical and Applied Pyrolysis

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A study of coal products obtained from Gray-King pyrolysis at 550 °C was carried out in order to obtain information about the chemical modifications of the huminite/vitrinite structure resulting from different processes of natural hydrogen-enrichment. The high oil yield obtained, the similarity between the infrared spectra of the generated oils and those of the parent vitrinite as well as the parallelism between the compositional data deduced for these oils and those obtained by means of Curie point pyrolysis-gas chromatography/mass spectrometry justify the use of this thermal approach. Gray-King pyrolysis is preferable to other techniques because it is possible to make an accurate mass balance, a thorough study of the solid residues and a full characterization of both the volatile and non-volatile fractions of the degradation products. From a study of selected perhydrous coals, mainly composed of the vitrinite maceral group, only in the low reflectance Jurassic coal from the Whitby (England) basin (WJVl) was the incorporation of lipoidal material evident, due to the significant contribution of long-chain alkyl aromatics in its oil. The structure of the vitrinite in the other Jurassic coals, the high reflectance sample from the Whitby basin (WJVh) and the coals from the Asturias (Spain) and Portugal basins (AJV and PGJV, respectively), is probably similar to that described for non-perhydrous vitrinites in the subbituminous coal rank. However, the presence of assimilated hydrogenated substances of a secondary nature, in particular for AJV and PGJV, hinders the cross-linking and condensation processes typical of the transit to the bituminous coal rank. In Cretaceous coals, from Teruel (Spain) and Utah (EEUU), (TCV and UCV, respectively), whose perhydrous character is mainly due to the specific hydrogenated nature of their botanical precursors, the incorporation of aliphatic structures via covalent oxygen linkages is proposed. The results obtained may be useful for establishing accurate structural models for perhydrous vitrinites. At the same time, the data obtained will contribute to explain the involvement of the high hydrogen content in the suppression of vitrinite reflectance

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“…A pyrolysis at slow heating rate was performed in an off-line open-medium system (GrayKing Assay Oven Type) following a procedure described by Suarez-Ruiz et al [12]. Vitrinite grains (≈1 mm size) were placed in a quartz reactor, with a temperature range of 300-450 °C.…”

Section: Pyrolysesmentioning

confidence: 99%

04/00051 Coking properties of perhydrous low-rank vitrains. Influence of pyrolysis conditions

2004

Fuel and Energy Abstracts

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Compositional transformations occurring during natural coalification generally lead to increased coking potential of coals characterised in the resulting cokes by large sizes of molecular orientation domains (MOD) determined through transmission electron microscopy with 002 dark field mode. In this study, two sets of perhydrous low-rank vitrains (WJV and UCV) have been pyrolysed using an open-system with two heating rates in an attempt to increase their coking potential. Results show that, despite the high potentialities of such vitrains for producing hydrocarbons, i.e. a suspensive medium efficient for their cokefaction, each of the pyrolysis methods does not lead to solid residues chemically equivalent to natural coking coals, since the cokes from these residues are always made of smaller MOD than those obtained for coking coals. For comparison, a similar characterisation, carried out on a conventional vitrain (Fouthiaux) pyrolysed in a confined-system which prevents the release of hydrocarbons, leads also to non-coking coals. The formation of such MOD is likely due to the peculiar chemical composition of the precursors and/or the pyrolysis conditions. FTIR data show that perhydrous vitrains are characterised by a low degree of condensation of aromatic units with a very small concentration of aromatic rings of large size. Thermal treatment originates depolymerisation reactions in the vitrinite network with the formation of low molecular weight products which are not efficient to form large anisotropic domains. The oxygen, present in relatively high amount in some vitrains (UCV and Fouthiaux) might also act as a crosslinking agent preventing the formation of large MOD. Furthermore, while openmedium pyrolysis leads to an important effluent release, as shown by the rapid decrease of H/C ratio, hydrocarbon effluents are conversely retained within the coal matrix in the case of confined-medium pyrolysis. However, the latter pyrolysis induces secondary cracking reactions leading to the formation of lighter products. Therefore, the enhancement of coking properties has not been totally reached by our experiments insofar as they did not lead to oxygen-poor artificially matured coals, similar to natural coking coals.

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Influence of rock particle size on the artificial thermal evolution of kerogen. A petrographic and geochemical study

Cited by 17 publications

References 6 publications

Chemical-structural changes during the thermal treatment of hydrogen-rich vitrinites caused by the presence of terpene-type resin

Chemical-structural changes during the thermal treatment of hydrogen-rich vitrinites caused by the presence of terpene-type resin

1D-NMR and 2D-NMR analysis of the thermal degradation products from vitrinites in relation to their natural hydrogen enrichment

04/00051 Coking properties of perhydrous low-rank vitrains. Influence of pyrolysis conditions

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