Nitrogen-enriched coal

Machnikowski, J., Grzyb, B., Weber, J.V., Frackowiak, E., Rouzaud, J.N., and Beguin, F. Structural and electrochemical characterization of nitrogen enriched carbons produced by the co-pyrolysis of coal-tar pitch with polyacrylonitrile. Electrochim. Acta 49, 2004 423-432. 

More recent studies were carried out with coals (lignite and subbituminous), enriched with nitrogen, before carbonization and activation, by treatment with ammonia and its derivatives, mainly urea [36,37]. The ammoxidation reaction (reaction with an ammonia-air mixture) is another route to obtaining nitrogen-enriched precursors of active carbons from various carbonaceous materials, such as pine wood, peat, lignite, subbituminous coal [38], and cellulose [39]. 

All these transformations take place in the region beyond the surface layer of the coal particle, where the gas phase is enriched with oxygen owing to intensive turbulent mixing. The final stage in the chain is NO formation from the monatomic nitrogen by the reactions ... 

The quality of anthracene obtained by this method is sufficient for the manufacture of anthraquinone by the usual processes. Because of hydrogen transfer during coal tar refining, the fore-runnings which arise during the distillation of the anthracene cake are enriched with 9,10-dihydroanthracene, which can be converted into anthracene by oxidation with air. This anthracene, recoverable by subsequent crystallization, is distinguished by an exceptionally low nitrogen content. 

In these studies, the nitrogen was introduced in the already activated carbons. Another way to prepare such active carbons is to start from coals enriched in nitrogen before the step of pyrolysis or activation [36,37], Two coals were selected a Polish subbituminous coal, preoxidized with performic acid, and a Russian lignite. Ammonia and its derivatives (ammonium carbonate, hydrazine, hydroxylamine, and urea) were applied as N-reagents [36,37], The N-rich-acti-vated carbons showed good oxidative removal activity for traces of hydrogen sulfide and for its oxidized by-products (elemental sulfur and sulfur dioxide) [36],... 

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