Chemical structure and thermal maturation of the vitrinite-like maceral in the Lower Paleozoic shales: Insights from Raman spectroscopy of artificial pyrolysis residues

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F23%3A00573708" target="_blank" >RIV/61389005:_____/23:00573708 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1016/j.jaap.2023.106024" target="_blank" >https://doi.org/10.1016/j.jaap.2023.106024</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jaap.2023.106024" target="_blank" >10.1016/j.jaap.2023.106024</a>

Result language

angličtina

Original language name

Chemical structure and thermal maturation of the vitrinite-like maceral in the Lower Paleozoic shales: Insights from Raman spectroscopy of artificial pyrolysis residues

Original language description

Vitrinite-like macerals (VLM) are ubiquitous in many pre-Devonian marine shales. The thermal maturity of these sediments, which are devoid of classical vitrinite, has been commonly evaluated using the reflectance of VLM as a substitute for vitrinite reflectance, but the molecular structure of VLM itself has seldom been examined. In this study, the immature VLM-rich Cambrian Alum shales from Scandinavia were selected and pyrolyzed at 300-550 celcius to acquire a series of artificial pyrolysis samples with different ranks. The molecular structures and thermal evolution of VLM in natural and artificial shales were investigated by Raman spectroscopy. These Raman spectra and optical properties were compared with those of vitrinite, graptolite, and solid bitumen. The Raman spectra of VLM in natural samples of variable thermal maturities and immature samples altered by pyrolysis were generally comparable. The reduction of WD (D band position) and FWHM-G (full width at half maximum of the G band) and the increase of WG (G band position) and AD/AG (area ratio) in VLM spectra, which parallels the increasing thermal maturity of the samples, indicated an increased degree of aromatic conjugation and more structurally ordered carbon moieties. The increase in wavenumber difference between the D and G bands positions in Raman spectra (Raman band separation, RBS) demonstrated the gradual removal of oxygen-containing functional groups, the loss of aliphatic side chains, and the increased degree of aromatic ring condensation. In this way, with progressing maturity, the molecular structure of VLM gradually evolved from heterocyclic aromatic compounds and amorphous carbon structures at low maturity levels to structurally better-ordered, larger, aromatic fused-ring units characteristic of post-to-over mature samples. These molecular structures and their changes associated with thermal maturation were similar to those known from classical vitrinite. Aside from its reflectance, the thermal maturity of VLM-rich sediments could be assessed by Raman spectroscopy, notably through the RBS parameter of VLM Raman spectra, which closely correlated with VLM random reflectance throughout the reflectance interval between 0.5% and 5.5%.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10406 - Analytical chemistry

Project

<a href="/en/project/EF16_019%2F0000728" target="_blank" >EF16_019/0000728: Ultra-trace isotope research in social and environmental studies using accelerator mass spectrometry</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2023

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Analytical and Applied Pyrolysis

ISSN

0165-2370

e-ISSN

1873-250X

Volume of the periodical

172

Issue of the periodical within the volume

JUN

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

15

Pages from-to

106024

UT code for WoS article

001015331600001

EID of the result in the Scopus database

2-s2.0-85160573700