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

Organic Geochemistry

By:
, , and
DOI: 10.1016/j.orggeochem.2008.01.007

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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. ?? 2008 Elsevier Ltd. All rights reserved.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Increasing maturity of kerogen type II reflected by alkylbenzene distribution from pyrolysis-gas chromatography-mass spectrometry
Series title:
Organic Geochemistry
DOI:
10.1016/j.orggeochem.2008.01.007
Volume
39
Issue:
4
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Organic Geochemistry
First page:
440
Last page:
449
Number of Pages:
10