Chapter 5
Maturation of Class Ib (Polylabdanoid) Resinites Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 24, 2015 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1995-0617.ch005
David J. Clifford and Patrick G. Hatcher Fuel Science Department, Pennsylvania State University, University Park, PA 16802-2303
Three polylabdanoid (Class Ib) resinites of increasing thermal maturity, which originated from the Goodwins, Giles Creek and Heaphy coal seams of New Zealand, were analyzed by solid-state nuclear magnetic resonance spectroscopy and pyrolysis-gas chromatography-mass spectrometry. The samples were analyzed as received and after Soxhlet extraction with dichloromethane and methanol. Observed maturation trends included depletion of exomethylenes (CPMAS C NMR) and increased abundance of alkylnaphthalenes and alkylhydronaphthalenes relative to compounds indicative of labdatriene precursors (py-GC-MS). Maturation pathways consistent with observed trends have been proposed. Considered reactions include exomethylene isomerization, further polymerization, cyclization and defunctionalization of the resinite polymer. 13
Polylabdanoid (Class lb) resinites are the semi-fossilized or fossilized remains of plant resins. Anderson et al. (4) define Class lb resinites as "derived from/based on polymers and copolymers of labdanoid diterpenes having the regular (IS, 4aR, 5S, 8aR) configuration" citing as examples resinites from New Zealand, Australia, and Siberia. Class lb resinites are thought to derive from polymerization of labdatriene precursors such as communie acid (Fig. la), communol (Fig. lb) and biformene (Fig. Ic) (1-3). They are formed via polymerization of the labdatriene precursors following contact with light and air as they are exuded from trees. Polymerization is thought to occur across the terminal side chain olefin yielding 14,15-polylabdatrienes (Fig. Id) (5). Entrapped within the polymeric network are non-polymerizing components of the source resin, which predominantly include abietanes and pimaranes such as dehydroabietic acid and sandaracopimaric acid, for example (6-9). Non-polymeric resinite components are readily characterized by conventional gas chromatography due to their intrinsic solubilities and volatilities. Following burial and subsequent maturation, polylabdanoid resinites undergo a very specific reaction resulting in depletion of the C8-C17 (Fig. 1) exomethylene, as determined by C nuclear magnetic resonance spectroscopy ( C NMR) (1-3) and fourier transform infrared (FTIR) spectroscopy (10-11). Recently, the exomethylene diminution was directly related to the polymeric fraction of Class lb resinites by C 1 3
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0097-6156/95/0617-0092$12.00/0 © 1995 American Chemical Society
In Amber, Resinite, and Fossil Resins; Anderson, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
5.
CLIFFORD & HATCHER
Maturation of Class lb (Polylabdanoid) Resinites
NMR analyses of extracted samples (12-13). As a result of their study, Clifford and Hatcher (13) established maturation trends based on pyrolysis-gas chromatographymass spectrometry (py-GC-MS) and C NMR data for a suite of resinites thought to have derived primarily from communie acid. The samples originated from the Yallourn and Morwell coal seams in Victoria, Australia and the Brunner coal measure of Nelson, New Zealand. C NMR results demonstrated a "loss" of one double bond per diterpenoid monomer with the persisting olefin containing a protonated and a nonprotonated carbon, as shown by Grimait et al. (8). Analyses of extracted samples by py-GC-MS displayed an increasing abundance of alkyl(hydro)naphthalenes relative to compounds directly related to polycommunic acid pyrolysis (i.e. hydronaphthenic acids). From these trends, the authors demonstrated inconsistencies in maturation schemes proposed in the literature to date (2-3, 14). The schemes included isomerization reactions (Fig. le) (2-3), exomethylene bonding (Fig. If) (14), and intramolecular polymerization reactions (Fig. lg) (14). It is the objective of this study to analyze a suite of Class lb resinites consisting primarily of communie acid/communol copolymers. The samples originate from the Goodwins, Giles Creek and Heaphy coal seams of New Zealand. They are thought to have derived primarily from the polymerization of communol and communie acid based on results of pyrolysis of the unextracted resinites (3, 15). For this study, pyGC-MS and C NMR analyses are conducted on the resinites as received and after Soxhlet extraction. Observed trends are compared with previously reported trends (12-13). 13
Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on September 24, 2015 | http://pubs.acs.org Publication Date: May 5, 1996 | doi: 10.1021/bk-1995-0617.ch005
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Samples and Methods For the purpose of this investigation, three Class lb resinites of diverse age and maturity were selected for characterization. Listed in Table I, in order of increasing maturity (rank of parent coal), are the sample origins, ranks of coal each can be associated with and elemental compositions. The resinites originate from the Goodwins, Giles Creek and Heaphy coal seams of New Zealand. Samples and elemental compositions were supplied by Dr. Ken B. Anderson (Amoco Oil Company, Naperville, IL) (16) and correspond to the samples described in Anderson et al. (3). Table I. Sample origins, ranks (parent coal) and elemental compositions Sample
Origin 15
Goodwins Giles Creek Heaphy b
b
Goodwins, New Zealand Giles Creek, New Zealand Heaphy, New Zealand
Rank (parent coal) lignite Β
%C 79.6
Elemental Data %N %S %H 0.04 10.2
