STRUCTURAL CHARACTERIZATION OF NITROGEN-ENRICHED COALS

A subbituminous coal and a lignite were treated with some nitrogen rea gents in several solvents with the aim of obtaining enriched coal samp les which could behave as active carbon precursors. This paper deals w ith the structural characterization of the samples obtained with urea before and after activation. The attention is focused on the identific ation of the main functional groups able to react with urea, on the na ture of the nitrogen functions introduced in the coal network, and on the behavior of these functions during the activation. The samples wer e investigated by infrared spectroscopy (DRIFT), X-ray photoelectron s pectroscopy(XPS). It was shown that ester/lactone and carboxylic acid groups are mainly concerned in the reaction with urea, which is solven t dependent. The identification of nitriles proved the occurrence of a mides in the first step of the reaction. The participation of ketones, though to a lesser extent, suggests the possibility of further hetero cyclization. The nitrogen enrichment of the coals is evidenced by XPS. On the basis of Literature data, four nitrogen groups were characteri zed according to the binding energies. They were assigned to pyrrolic and several pyridinic forms. Their behavior during thermal treatments and steam activation is discussed.