FTIR quantification of the functional C groups in coals and extraterrestrial kerogens: a calibration procedure

Thi Hai Van Phan (1) , Eric Quirico (1) , Pierre Beck (1) , Nathalie Carrasco (2, 3) , Thomas Gautier (3) , Lora Jovanovic (3) , Jesus Raya (4) , Yann Le Brech (5) , Corentin Le Guillou (6)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 IUF - Institut universitaire de France
3 PLANETO - LATMOS
4 UNISTRA - Université de Strasbourg
5 LRGP - Laboratoire Réactions et Génie des Procédés
6 UMET - Unité Matériaux et Transformations - UMR 8207

Kerogens and coals are complex polyaromatic carbonaceous solids that formed in Earth sediments from the thermal maturation and preservation of living organisms[1]. Kerogen-like polyaromatic materials are also present in primitive meteorites, presumably formed in the proto-solar disk through thermal and/or radiolytic reactions and were further processed in their parent bodies [2]. Though decades of analytical investigations, the composition and chemical structure of those materials remain not fully elucidated. FTIR (Fourier-Transform Infrared Spectros-copy) has been proved to be a powerful technique for characterizing coals, peats, terrestrial and meteoritic kerogens [2]–[4]. However, the quantification of functional C groups by calculating of the integrated cross-section of each functional C groups is hampered by the lackof precise knowledge of their integrated cross-sections. Our present workaims to investigate the infrared spectra usingthe different standards as known polymers [5]and synthetic polyaromatic materials(e.g. tholin), produced by thermal degradations of a 13C-substituted precursor. It was synthesized in a cold plasma reactor(PAMPRE, Latmos, Guyancourt) from a 13CH4: 13CO = 7: 3 gas mixture with 90% of Ar [6]. Characterization of known molecular polymer and the carbonized tholin were performed and Nuclear Magnetic Resonance(NMR)measurements were then run, providing estimates of the integrated cross-sections ratio of the aromatic, C=C, C=O and CHxgroups. The carbonizationprocess canincrease the polyaromatic characterin the tholin compositiontoward a structure similar to that observed in these terrestrial and extraterrestrial materials. We will present the whole calibration procedure and applications to the quantification of the above-mentioned functional groups for coal and meteoritic kerogen samples. A series of coalswith different vitrinite reflectancesand some FTIR data of IOM samples from chondrites will be re-calculated to compare with the previous data to see the contribution of the relative abundance of carbon atoms regrading to the C=C, C=O, CH3, CH2and aromatic groups

Domaines: Planète et Univers [physics]

Thi Hai Van Phan, Eric Quirico, Pierre Beck, Nathalie Carrasco, Thomas Gautier, et al.. FTIR quantification of the functional C groups in coals and extraterrestrial kerogens: a calibration procedure. MetSoc 2019, The 82nd Annual Meeting of The Meteoritical Society 2019, Jul 2019, Sapporo, Japan. pp.LPIContrib.No.2157. ⟨insu-02182508⟩