Date of Graduation
The dissolution effectiveness of a solvent solution of 50% aqueous sodium hydroxide and elemental sulfur was studied. The effects of varying amounts of added elemental sulfur (from 0.5% to 50% of the weight of the coal plus sulfur) over a temperature range of 100(DEGREES)C to 250(DEGREES)C and reaction times from 10 minutes to 3 hours were examined. The coals used in the study were a Bakerstown bituminous, a Wyodak subbituminous, a North Dakota lignite, and a Savage lignite. The reaction of the dissolution products with carbon monoxide and water in a basic system with iron pentacarbonyl as catalyst was also examined. The dissolution of Wyodak subbituminous and North Dakota lignite coals (moisture and ash-free basis) in 50% NaOH solution was doubled by the presence of elemental sulfur. Average dissolution for these coals in the aqueous NaOH/sulfur system was approximately 55% with a maximum of 70%. Additional sulfur up to 50% of the weight of the coal did not further enhance dissolution. Dissolution of Bakerstown bituminous coal (moisture and ash-fee basis) in 50% NaOH solution appeared unaffected by the presence of sulfur. Desulfurization occurred in all coal residues during simple dissolution. Dissolution followed by treatment with carbon monoxide resulted in a decrease in measured dissolution for both Bakerstown bituminous and Wyodak subbituminous coals as compared to dissolution alone. This treatment also resulted in a benzene-extractable product in the filtrates of a subbituminous coal which had a H/C ratio of 1.1. No comparable product was obtained from the benzene extraction of filtrates subjected only to dissolution. Dissolution appears to be caused by the aqueous NaOH/sulfur solvent attacking susceptible oxygen containing functionalities (e.g. ethers, esters, and carboxylic acids) in the coal. These observations are consistent with the known action of NaOH on these functionalities. The intercalation of sulfur or sulfur compounds into the coal may allow further reaction with the solvent. This appears to be one of several possible mechanisms explaining the enhanced dissolution in the NaOH/sulfur system.
Dorland, Dianne, "Low Temperature Dissolution Of Coal." (1985). Graduate Theses, Dissertations, and Problem Reports. 8773.