Functional composition of the surface layer of metamorphism series coals according to X-ray photoelectron spectroscopy
P. N. KUZNETSOV1, B. AVID2, L. I. KUZNETSOVA1, A. V. OBUKHOVA1, E. S. KAMENSKIY1, O. A. EPOV1
1Krasnoyarsk Scientific Centre SB RAS, Institute of Chemistry and Chemical Technology SB RAS, Krasnoyarsk, Russia
2Institute of Chemistry and Chemical Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
Keywords: coal, molecular structure, surface layer composition, X-ray photoelectron spectroscopy
Abstract
The features of the composition of carbon and heteroatomic functional groups on the surface of carbonification series coals, oxygen and nitrogen distribution over the surface and volume have been characterised by X-ray photoelectron spectroscopy. It has been established that oxygen in brown coals is almost equally represented on the surface and in volume. The surface of hard coals is enriched in oxygen-containing groups, and their concentration in coking coals significantly exceeds the volume concentration. Carbon is present on the surface mainly in polycondensed aromatic (graphite-like) structures. Their proportion and degree of uniformity increase with carbonification. The oxidised forms of carbon are present on the surface mainly in the form of phenolic and ether groups. Heteroatomic nitrogen-containing groups are represented by aromatic, mainly five-membered pyrrole, to a lesser extent six-membered pyridine structures. It is shown that as carbonification degree increases, the five-membered cycles in coals are transformed into six-membered cycles.
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