Formation of CO2, H2 and condensed carbon from siderite dissolution in the 200–300°C range and at 50MPa
Vincent Milesi
(1)
,
François Guyot
(2)
,
Fabrice Brunet
(3)
,
Laurent Richard
(4)
,
Nadir Recham
(5, 6)
,
Marc Benedetti
(1)
,
Julien Dairou
(7)
,
Alain Prinzhofer
(8)
1
IPGP -
Institut de Physique du Globe de Paris
2 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
3 ISTerre - Institut des Sciences de la Terre
4 Carrer de Pontevedra 45-3-2, 08003 Barcelona, Spain
5 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314 UPJV
6 RS2E - Réseau sur le stockage électrochimique de l'énergie
7 BFA (UMR_8251 / U1133) - Unité de Biologie Fonctionnelle et Adaptative
8 Geo4U
2 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
3 ISTerre - Institut des Sciences de la Terre
4 Carrer de Pontevedra 45-3-2, 08003 Barcelona, Spain
5 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314 UPJV
6 RS2E - Réseau sur le stockage électrochimique de l'énergie
7 BFA (UMR_8251 / U1133) - Unité de Biologie Fonctionnelle et Adaptative
8 Geo4U
Résumé
Laboratory experiments were conducted to investigate the chemical processes governing the carbon speciation associated to hydrothermal decomposition of siderite. Experiments were carried out in sealed gold capsules using synthetic siderite and deionised water. The samples were reacted at 200 and 300°C, under a pressure of 50 MPa. Siderite dissolved to reach the 3FeCO3 + H2O = Fe3O4 + 3CO2 + H2 equilibrium and magnetite, Fe3O4, was produced accordingly. The gas phase was dominated by CO2, H2 and CH4, the latter being in strong thermodynamic disequilibrium with CO2. Contrary to the other gas products, H2 concentration was found to decrease with run duration. TEM observations showed the occurrence of condensed carbon phases at the surfaces of magnetite and residual siderite grains.
Thermodynamic calculations predict the formation of condensed carbon in the experiments according to the reaction: CO2 + 2H2 = C + 2H2O, which accounted for the observed H2 concentration decrease up to the point where H2 and CO2 activities were buffered by the graphite-siderite-magnetite assemblage. The well-organized structure of the carbon coating around magnetite emphasizes the high catalytic potential of magnetite surface for carbon reduction and polymerization. The formation of such C-rich phases may represent a potential source of CH4 by hydrogenation. On the other hand, the catalysis of Fischer-Trospch type reactions may be poisoned by the presence of carbon coating on mineral surfaces. In any case, this study also demonstrates that abiotic H2 generation by water reduction, widely studied in recent years in ultrabasic contexts, can also occur in sedimentary contexts where siderite is present. We show that, in the latter case, natural H2 concentration will be buffered by a condensed carbon phase associated with magnetite.
Domaines
Planète et Univers [physics]Format du dépôt | Fichier |
---|---|
Type de dépôt | Article dans une revue |
Titre |
en
Formation of CO2, H2 and condensed carbon from siderite dissolution in the 200–300°C range and at 50MPa
|
Résumé |
en
Laboratory experiments were conducted to investigate the chemical processes governing the carbon speciation associated to hydrothermal decomposition of siderite. Experiments were carried out in sealed gold capsules using synthetic siderite and deionised water. The samples were reacted at 200 and 300°C, under a pressure of 50 MPa. Siderite dissolved to reach the 3FeCO3 + H2O = Fe3O4 + 3CO2 + H2 equilibrium and magnetite, Fe3O4, was produced accordingly. The gas phase was dominated by CO2, H2 and CH4, the latter being in strong thermodynamic disequilibrium with CO2. Contrary to the other gas products, H2 concentration was found to decrease with run duration. TEM observations showed the occurrence of condensed carbon phases at the surfaces of magnetite and residual siderite grains.
Thermodynamic calculations predict the formation of condensed carbon in the experiments according to the reaction: CO2 + 2H2 = C + 2H2O, which accounted for the observed H2 concentration decrease up to the point where H2 and CO2 activities were buffered by the graphite-siderite-magnetite assemblage. The well-organized structure of the carbon coating around magnetite emphasizes the high catalytic potential of magnetite surface for carbon reduction and polymerization. The formation of such C-rich phases may represent a potential source of CH4 by hydrogenation. On the other hand, the catalysis of Fischer-Trospch type reactions may be poisoned by the presence of carbon coating on mineral surfaces. In any case, this study also demonstrates that abiotic H2 generation by water reduction, widely studied in recent years in ultrabasic contexts, can also occur in sedimentary contexts where siderite is present. We show that, in the latter case, natural H2 concentration will be buffered by a condensed carbon phase associated with magnetite.
|
Auteur(s) |
Vincent Milesi
1
, François Guyot
2
, Fabrice Brunet
3
, Laurent Richard
4
, Nadir Recham
5, 6
, Marc Benedetti
1
, Julien Dairou
7
, Alain Prinzhofer
8
1
IPGP -
Institut de Physique du Globe de Paris
( 250059 )
- IPGP, 1 rue Jussieu, 75238 Paris cedex 05 ; Université Paris Diderot, Bât. Lamarck A case postale 7011, 75205 Paris CEDEX 13
- France
2
IMPMC -
Institut de minéralogie, de physique des matériaux et de cosmochimie
( 247163 )
- Tour 23 - Barre 22-23 - 4e étage - BC 115 - 4 place Jussieu - 75252 Paris
- France
3
ISTerre -
Institut des Sciences de la Terre
( 222134 )
- BP 53 - 38041 Grenoble cedex 9
- France
4
Carrer de Pontevedra 45-3-2, 08003 Barcelona, Spain
( 1041721 )
- Carrer de Pontevedra 45-3-2, 08003 Barcelona, Spain
- Espagne
5
LRCS -
Laboratoire réactivité et chimie des solides - UMR CNRS 7314 UPJV
( 199933 )
- Université de Picardie Jules Verne - 33 Rue Saint-Leu - 80039 AMIENS CEDEX 1
- France
6
RS2E -
Réseau sur le stockage électrochimique de l'énergie
( 216126 )
- Université de Picardie Jules Verne - 33 rue Saint-Leu - 80039 AMIENS CEDEX 1
- France
7
BFA (UMR_8251 / U1133) -
Unité de Biologie Fonctionnelle et Adaptative
( 244703 )
- Université Paris Diderot, Bât. Buffon, 4 rue Marie-Andrée Lagroua Weill-Hallé, case postale 7081 , 75205 Paris cedex 13
- France
8
Geo4U
( 566467 )
- Rio de Janeiro
- Brésil
|
Vulgarisation |
Non
|
Comité de lecture |
Oui
|
Audience |
Internationale
|
Langue du document |
Anglais
|
Nom de la revue |
|
Date de publication |
2015-04
|
Volume |
154
|
Page/Identifiant |
201-211
|
Domaine(s) |
|
DOI | 10.1016/j.gca.2015.01.015 |
Origine :
Fichiers produits par l'(les) auteur(s)
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