Thermodynamic and kinetic study of coal and model compound desulfurization with supercritical methanol
This study is a theoretical and experimental study of some aspects of coal desulfurization by the supercritical methanol extraction (SME) method. With this desulfurization process, both organic and inorganic sulfur are selectively removed from coal. Thermodynamic calculations based on minimization of Gibbs free energy of a mixture of identified products in the supercritical phase indicated that hydrogen sulfide should be the dominant final sulfur containing product. Several model compounds were used to study the desulfurization mechanism and the effectiveness of SME for different organo-sulfur functional groups and pyrite. The desulfurization pathway is concluded to be that the sulfur in coal is removed by reacting with methanol and/or its degradation products directly to produce solvent derived sulfur containing intermediates which decompose to hydrogen sulfide as the ultimate sulfur product. Both disulfide and thiol groups were active under SME, while dibenzo thiophene appeared to be very inert. Only simple disulfides, sulfides, thiols and hydrogen sulfide exist in the product when only straight chain structures were involved in the reaction. Many complex compounds are produced besides the above products when aromatic structures were involved in the reaction. The reaction rate of sulfur removal from pyrite was fast under severer reaction conditions. However, regressive reactions (i.e., recombination of sulfur from the supercritical phase with the iron/sulfur minerals) occur after the pyrite reaches its maximum sulfur removal. Different coals had different extents of desulfurisation under SME depending on the rank and the pyrite content. Higher desulfurisation was attained for the lower rank coal. Because of the regressive reactions of pyrite. the desulfurization of the high pyrite sulfur content coal was limited by these regressive reactions. Sulfur was selectively removed for most of the coals under most of the reaction conditions.
- Research Organization:
- Southern Illinois Univ., Carbondale, IL (United States)
- OSTI ID:
- 7078894
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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