A PROCEDURE FOR THE PRODUCTION OF ULTRA-PURE PRECURSORS FROM COAL FORTHE MANUFACTURE OF VALUE-ADDED CARBON PRODUCTS - PREPARATION OF AN EXTRACT

Solvent extraction is a potential technique for the production of coal -derived extracts which may be suitable as precursors for value-added carbon products. At present, the development of new and non-convention al markets for coal has resulted in the exploration of new application s such as slurry fuels, coal-based graphites, carbon-carbon composites and carbon anodes. However, for carbon products to perform acceptably in such applications, the ash content of the precursor must be less t han 0.1%. Although, work to produce a low-ash (ca. 0.2%), low-sulfur c oal-derived material had begun about a decade ago through solvent extr action using the solvent NMP (N-methyl-2-pyrrolidone), it was practica lly impossible to produce a coal-derived extract containing less than 0.2% ash. This is due to the presence of ultra-fine mineral matter par ticles and solvent soluble inorganic species. The principal objective of the present work was to investigate techniques for the separation o f the coal-derived extract from the NMP-coal suspension after solvent extraction and to produce a ultra low-ash precursor. The significant c ontribution of this work was the development of a rigorous technique w hich has been implemented to produce coal-derived extracts with less t han 0.1% ash. The existing solvent recovery procedure has been modifie d to exclude the presence of NMP-soluble inorganics which re-precipita ted on the coal-derived extracts and were difficult to eliminate in th e product extract. It has been shown that the alternate route of water -precipitation preferentially precipitates the coal-derived extract fr om the coal-NMP suspension with the NMP-water phase retaining most of the soluble inorganic species. Although, this technique does require s ubsequent solvent recovery from the water-phase by distillation, it re duces the concentration of ash in the extract, which can now be used t o manufacture ultra-pure carbon precursors for specialized application s.