Date of Award
Doctor of Philosophy (PhD)
Chemistry and Biochemistry
Patrick G. Hatcher
James W. Lee
The thermal maturation and alternation of vascular plant material into coals and as expelled petroleum-like compounds is the main focus of this dissertation. Utilizing artificial maturation studies, like hydrothermal liquefaction, yields useful information regarding how plant material is preserved in coals and the potential certain plant biopolymers possess to generate liquid fuels is acquired. The studies within this dissertation focus on utilizing the aliphatic biopolymers, cutin, cutan, and suberan, found in the epidermis of certain plants. These biopolymers contain minimal amounts of heteroatoms and are comprised of long polymethylenic chains, which are desirable characteristics in generating bio-oils. Additionally, understanding the chemical alterations that occur to these biopolymers during maturation is essential in evaluating their geochemical preservation in coals.
To evaluate the potential suberan has to become incorporated into coals and generate expelled oils, hydrothermal liquefaction experiments were conducted on modern, Betula alleghaniensis bark, and ancient, a lignite rich in crypto-eugelinite, samples. Both the bark and the coal display characteristic crystalline and amorphous peaks in solid-state 13C NMR, which is indicative of the presence of suberan. The expelled oil products of both feedstocks were mainly comprised of saturated hydrocarbons. These results suggest that suberan can readily explain the existence of waxy crude oils typically associated with coals and Type III source rocks.
The oil generating potential of cutan and cutin were evaluated using skins collected from Agave americana and Capsicum annumm. Both cuticular materials resulted in approximately 35% wt.% bio-oil yields and exhibited heating values of 40.5 MJ kg-1, comparable to those of typical crude petroleum. Furthermore, a two-step hydrothermal liquefaction experiment was successfully employed to reduce the heteroatom content of the produced Agave americana bio-oil.
Another focus of this dissertation is understanding the fate of plant materials during peatification and coalification. Humic acids were isolated from several peat swamps across the U.S. as well as a low rank collected from the Yallourn Open Cut in Australia, and analyzed using high resolution mass spectrometry and solid-state 13C NMR. From these analyses photochemically produced particulate organic matter was observed in all the samples. The presence of this material in peats and coals can likely explain the origin of ubiquitously occurring fusinite, macrinite, micrinite, and related inertinite macerals in coal.
Hartman, Blaine E.. "Artificial Maturation Studies of Polymethylenic Plant Biopolymers: Investigating the Chemical Alterations from Plant Material to Coal" (2015). Doctor of Philosophy (PhD), dissertation, Chemistry and Biochemistry, Old Dominion University, https://digitalcommons.odu.edu/chemistry_etds/3