Date of Award
Master of Science
Oxidative Hydrothermal Dissolution (OHD) is a coal conversion technique developed at SIUC that solubilizes coal by mild oxidation using molecular oxygen and hydrothermal water. Products are generally low-molecular-weight organic acids that could be used as chemical feedstocks. This project examined the influence of coal lithotype composition and pure maceral concentrates on the OHD process with a focus on reaction rate and products. Hand-picked lithotypes (vitrain, clarain, and fusain) from the Herrin, Springfield, and Murphysboro seams, as well as a cannel coal from the Brazil Block seam were subjected to OHD for 8, 16, 30, and 70 min. The 70-min run was a completion run whereas other times were pulse (incomplete reaction) runs. No significant differences were found in the OHD products even though previous work suggested maceral composition could affect final products. Most samples produced primarily mono- and di-acids due to the rank of the coal (high volatile bituminous). Pulse runs allowed for petrographic examination of the residue. OHD preferentially reacted with vitrinites and liptinites over the inertinites. Collodetrinite generally developed vacuoles before collotelinite whereas collotelinite developed reaction rims by 8-min. Liptinites developed reaction rims and loss of fluorescence. Semifusinites showed slight reaction rims at 8 min, though generally, inertinites did not display pronounced reaction rims until 30 min. Samples run under hydrolysis conditions revealed vacuoles and reaction rims could be produced with heat and pressure, but OHD conditions accelerate their production. Maceral concentrates produced different OHD products. Vitrinites and inertinites produced a similar suite of products with individual macerals missing a few products. Liptinite macerals (cutinite and sporinite) produced a different suite of products containing aliphatic acids as well as some products common to the vitrinites and inertinites. The cutinite suite was primarily aliphatic containing few aromatic compounds. The sporinite contained a mix of aliphatic and aromatic compounds. Vitrinites and inertinites produced a mix of mono-, di-, and tri-acids. Similarities in products between the vitrinites and inertinites are likely due to their origins from similar plant tissues (mostly woody material) that have undergone varying degrees of alteration by partial combustion, oxidation, etc. These similarities suggest that high inertinite coals could potentially produce similar OHD products to coals rich in vitrinite. The different products obtained from the macerals do suggest the potential for the OHD process to be tailored to produce specific compounds by varying the feedstock.
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