Date of Award

Summer 2011

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry & Biochemistry

Program/Concentration

Chemistry

Committee Director

Jingdong Mao

Committee Member

Patrick G. Hatcher

Committee Member

Kenneth Mopper

Committee Member

Jennifer Poutsma

Abstract

Variations in the chemical structures of kerogens From highly volatile bituminous coal located near two igneous dike intrusions in the Illinois Basin were examined in detail by advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Spectral-editing techniques were used to identify specific functional groups. Direct polarization was used to quantify different functional groups. 1H-13C two- dimensional heteronuclear NMR was used to examine connectivities and proximities, and 1H-13C long-range recoupled dipolar dephasing was used to estimate aromatic cluster sizes. With decreasing distance to dike contacts and increasing thermal maturity (vitrinite reflectance R0 from 0.62% to 5.03%), new insights into the chemical structural changes in coal kerogens include (i) the C(CH2)C groups were removed faster than CCH3 groups, suggesting that the major cleavage of aliphatics should not occur at aryl rings, (ii) a progressive decrease of the relative abundance of protonatcd aromatic carbons, possibly due to replacement of aromatic hydrogens by aryl groups via cross-linking, and (iii) an increase in the aromatic cluster size, in addition to the well-known changes of the elimination of aliphatics and aromatic C-0 groups and an increase in aromaticity. For the first time, the growth of aromatic cluster sizes with increasing maturity was quantitatively estimated. Another novel finding is that coal kerogen (kerogen ¹22) directly in contact with the large dike retained considerable aliphatic components. This kerogen could have

been entrapped and would have failed to diffuse out rapidly enough due to intense and rapid heating, rendering this kerogen partially fluidized. Thermal maturation of kerogens due to magmatic intrusions may be different from that of long-term geologic heating. Type III coal kerogens used in the present study show documentation that the increase of aromaticity with increasing R0, is due to the removal of aliphatics accompanied by the increase in aromatic cluster sizes. In contrast, our previous NMR study on a series of Type II kerogens (R0, from 0.29% to to 1.27 %), that have experienced long-term heating, indicate that the increase of aromaticity with increasing R, was mainly related to the shortening of aliphatic chains attached to the aromatic cores, without significant growth of fused aromatic rings.

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DOI

10.25777/y86m-0e86

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