Increasing maturity of kerogen type II reflected by alkylbenzene distribution from pyrolysis-gas chromatography–mass spectrometry

GP Lis, M Mastalerz, A Schimmelmann

Research output: Contribution to journalArticle (Academic Journal)peer-review

15 Citations (Scopus)

Abstract

A series of Late Devonian to Early Mississippian type II kerogens with vitrinite reflectance values Ro 0.29–2.41% were analyzed using py-GC–MS. In addition, a low maturity kerogen with Ro 0.44% was separated into fractions via density gradient centrifugation, followed by py-GC–MS of the alginite and amorphinite maceral concentrates. Alkylbenzenes and n-alk-1-ene/n-alkane doublets represented the main compound classes identified in all pyrolysates. The pyrolysate from alginite featured 1,2,4-trimethylbenzene and toluene as the two most prominent alkylbenzenes. In contrast, alkylbenzenes in pyrolysates from amorphinite and low maturity bulk kerogens with Ro 0.29–0.63% were dominated by 1,2,3,4-tetramethylbenzene. With increasing thermal maturity, pyrolysates were increasingly dominated by (i) alkylbenzenes with fewer methyl groups, namely by tri- and dimethylbenzenes at medium maturity (Ro 0.69–1.19%), and (ii) by toluene at higher maturity (Ro 1.30–2.41%). With increasing maturity of kerogen type II, the decreasing abundance of highly methyl-substituted alkylbenzenes and the parallel increase in less methyl-substituted alkylbenzenes in flash pyrolysates suggest that demethylation is an important chemical process in the thermal maturation of kerogen type II.
Translated title of the contributionIncreasing maturity of kerogen type II reflected by alkylbenzene distribution from pyrolysis-gas chromatography–mass spectrometry
Original languageEnglish
Pages (from-to)440 - 449
JournalOrganic Geochemistry
Volume39
DOIs
Publication statusPublished - 2008

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