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

Lis, GP; Mastalerz, M; Schimmelmann, A

HERO ID

994835

Reference Type

Journal Article

Year

2008

HERO ID 994835
In Press No
Year 2008
Title Increasing maturity of kerogen type II reflected by alkylbenzene distribution from pyrolysis-gas chromatography–mass spectrometry
Authors Lis, GP; Mastalerz, M; Schimmelmann, A
Journal Organic Geochemistry
Volume 39
Issue 4
Page Numbers 440-449
Abstract A series of Late Devonian to Early Mississippian type II kerogens with vitrinite reflectance values R-o 0.29-2.41% were analyzed using py-GC-MS. In addition, a low maturity kerogen with R-o 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-l-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 R-o 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 (R-o 0.69-1.19%), and (ii) by toluene at higher maturity (R-o 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. (c) 2008 Elsevier Ltd. All rights reserved.
Doi 10.1016/j.orggeochem.2008.01.007
Wosid WOS:000256125900006
Url http://linkinghub.elsevier.com/retrieve/pii/S0146638008000119
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