Thesis (Ph.D.)--University of Tulsa, 1985. / Bibliography: leaves 186-192.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 156-168).

Thesis (M.S.)--Ohio University, June, 1993. / Title from PDF t.p.

Thesis (Ph. D.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 195).

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Carter, W.B.; Committee Member: Cochran, Joseph; Committee Member: Venugopal, Ganesh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Two types of Mo₂C have been investigated: polycrystalline β-Mo₂C and single crystal α-Mo₂C. The β-Mo₂C material was synthesized via a temperature-programmed method, and then characterized using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), CO chemisorption, and N₂ physisorption. The catalytic activity of the β-Mo₂C was tested for cumene hydrogenation under high pressure conditions, and the effect of sulfur and oxygen poisons on cumene hydrogenation was also investigated. As a complement to the work done on polycrystalline β-Mo₂C, UHV studies of single crystal α-Mo₂C were undertaken to provide fundamental information about a well-characterized Mo₂C surface. The (0001) surface of α-Mo₂C was investigated using XPS and low energy electron diffraction (LEED). It was found that an ion-bombarded surface could be prepared as either Mo-terminated or C-terminated by choosing either low annealing temperatures (~1000 K) or high annealing temperatures (~1500 K), respectively. CO and O₂ adsorption was also studied on α-Mo₂C (0001) using thermal desorption spectroscopy (TDS), XPS, Auger electron spectroscopy (AES), and LEED. Finally, thiophene adsorption was investigated on α-Mo₂C (0001). / Ph. D.

Flue gas desulfurization (FGD) is utilized by the coal-powered generating industry to safely eliminate sulfur dioxide. A FGD vessel (scrubber) synthetically creates gypsum crystals by combining limestone (CaCO3), SO2 flue gas, water and oxygen resulting in crystalline gypsum (CaSO4 ∙ 2H2O), which can be sold for an economic return. Flat disk-like crystals, opposed to rod-like crystals, are hard to dewater, lowering economic return. The objectives were to investigate the cause of varying morphologies, understand the environment of precipitation, as well as identify correlations between operating conditions and resulting unfavorable gypsum crystal growth. Results show evidence supporting airborne impurities due to the onsite coal pile, the abundance and size of CaCO3 and high Ca:SO4 ratios within the scrubber as possible factors controlling gypsum crystal morphology. In conclusion, regularly purging the system and incorporating a filter on the air intake valve will provide an economic byproduct avoiding costly landfill deposits.

No description available.

No description available.

The precombustion desulfurization of coal was investigated by photochemical methods and by the application of a novel pyrite depressant in froth flotation. Semiconductor photoelectrochemical catalysis was extensively examined. As much as 41% of the organic sulfur was removed and 72% overall desulfurization of micronized Illinois No. 2 coal was obtained. Zinc oxide, in colloidal suspension, produced a small increase in the overall desulfurization at longer reaction times when compared to direct photolysis. The major limiting factor in organic sulfur removal from coal appears to be accessibility rather than reactivity. Kinetic experiments conducted with the model organosulfur compound, dibenzothiophene, showed high photochemical reactivity with nearly complete conversion occurring in 5 minutes in a saturated solution at 25°C. Scanning electron microscopic examination of product coals showed empty casts in places once occupied by iron pyrite. Additionally, a novel process was developed for separating clean coal from metal sulfide minerals such as pyrite and marcasite. The process comprises depressing the metal sulfide minerals with a reagent resulting from the alkaline oxidation and polymerization of a polyphenol or a quinone, and selectively floating clean coal from the depressed metal sulfide minerals. The process was investigated using microflotation, conventional Denver cell flotation, and microbubble column flotation. Up to 90% pyritic sulfur rejection was achieved from a coal and coal pyrite synthetic mixture. The process efficiency is a function of pH with greater improvements generally occurring at acidic pH when compared with the results obtained in the absence of the quinonoid reagent. However, in the case of microbubble column flotation with micronized coals, the largest overall pyritic sulfur and ash rejection occurred under alkaline conditions. Data from x-ray photoelectron spectroscopy and calorimetry indicate the quinonoid reagent modified the surface properties of minerals by reversible adsorption. / Ph. D.