Date of Award
Doctor of Philosophy
The Oxidative Hydrothermal Dissolution (OHD) process was developed at Southern Illinois University to convert solid organic material to low-molecular-weight, water-soluble products using small amounts of dissolved oxygen in liquid water at high temperature and pressure. The process is environmentally friendly; it does not involve the use of solvents or catalysts, and there is little emission of CO2 and no emission of NOx or SOx. Previous studies of the effects of OHD on organic matter have focused on coal, coal waste, and biomass. This study explores the application of OHD to organic-rich shales, providing a baseline investigation into how highly aliphatic materials react under OHD conditions, what types of products are created during the process, whether the products are economically valuable, and whether they provide novel structural and biomarker information that complements typical bulk organic matter characterization methods. Furthermore, typical oil shale utilization methods are plagued by environmental concerns akin, in some respects, to the environmental concerns associated with the coal industry. The successful application of OHD to these materials would provide a cleaner, more efficient way to process oil shale, resulting in an aqueous product that can be transported through pipelines and refined using conventional processing technology. To examine how OHD affects oil shale kerogen, a series of partial conversion experiments were conducted on an Alpha Torbanite sample at varied temperatures, reaction times, and oxidant inputs. Using a fixed-bed type reactor, over 90% carbon conversion was achieved in just 10-12 minutes under relatively mild reaction conditions (300°C) with little gas production, approximately twice as fast as OHD coal conversion. GC-MS analyses of the product distributions for these experiments demonstrate that they do not change significantly under varying reaction conditions, which can be adjusted for maximum carbon conversion. A sample of each type of oil shale (torbanite: Alpha Torbanite, lamosite: Green River Formation, marinite: New Albany Shale, tasmanite: Tasmanian tasmanite, kuckersite: Decorah Formation, cannel: Cannel King) was reacted and analyzed for product distributions. All of the oil shales produced a complex mixture of aliphatic carboxylic acids, dicarboxylic acids, keto-acids, aromatic acids, and poly-acids, some of which include phenolic structures. These products include materials that are useful as chemical feedstocks for the manufacture of plasticizers, nylons, polymers, lubricants, nylons, paints, and a variety of other materials, most of which are currently produced from petroleum derived precursors. Results of OHD biomarker analysis were not comparable to conventional solvent extraction results. With the exception of the Green River sample which did produce favorable results, analyzed steranes and hopanes were not present in measurable/identifiable amounts in the OHD products. It is unclear whether the biomarker peaks are buried under unresolved products or if the biomarkers are oxidizing/degrading under OHD conditions. However, a comparison of OHD product distributions to pyrolysate product distributions demonstrates that this method provides novel information regarding the original macromolecular structure of the kerogen. Since OHD converts a larger fraction of the original carbon, this approach may provide a more complete/correct representation of the initial structure than conventional methods.
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