Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula

Abstract

The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal) from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative, due to a number of interferences, such as spinning side bands (SSB) in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin, Northern Greece, is relatively unaltered and largely unweathered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonances for methoxyl, phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.