Date of Graduation
Alkali materials exist in coal in both inorganic and organic forms. As a means of studying the release of alkali material from the organic phase, sodium and potassium benzoate have been chosen as model compounds. The decomposition of these two compounds, in terms of both gaseous species and residues, have been studied in argon, carbon dioxide, and air. Thermogravimetric methods were used to determine the different ranges where decomposition occurred and to obtain kinetic information. Pyrolysis-gas chromatography was used to identify the various organic products formed from the decomposition of the benzoates below 600(DEGREES)C. Transpiration mass spectrometry at pressures up to 0.3 atm. of argon was used to identify and to measure the partial pressures of different gaseous products. At temperatures below 550(DEGREES)C, the decomposition comprises of organic loss and is nearly independent of the atmosphere. At this temperature, the residue left from the decomposition is a mixture of carbonate and char. The most important organic products are benzene, biphenyl, substituted biphenyls, fluorene, anthraquinone, phenanthraquinone, and fluorene. Above 550(DEGREES)C, the atmosphere in which the decomposition is carried out becomes important. In argon, alkali release occurs at temperature above 700(DEGREES)C. In the presence of carbon dioxide, the carbonate is stabilized and decomposes at temperatures above 1100(DEGREES)C to release alkali. At an intermediate temperature, catalyzed gasification of the char residue occurs. For gasification, potassium carbonate is a better catalyst than sodium carbonate. In air, the carbonate is not stabilized and hence decomposes at a lower temperature. The gasification step also occurs at a lower temperature than in carbon dioxide. For the decomposition in argon atmosphere, activation energy was determined for the reaction leading to organic loss and for the reaction causing alkali release. Heat of the second reaction was also determined for both the model compounds.
Chakrabarti, Ashok, "Alkali Release From Model Coal Compounds." (1981). Graduate Theses, Dissertations, and Problem Reports. 8596.