Analysis and characterization of ash-free coals from the Pechora coal basin obtained by organic solvent extraction

The probability of obtaining of ash-free coal extracts, so-called "hyper-coals," has been shown for coals of the Pechora basin for the first time. The ash content in them does not exceed a few percent, whereas initial coals contain up to 20% ash. High-resolution ¹³C NMR shows the similarity in the structure of the initial coal and the extract. It is demonstrated that the solvent selected for hyper-coal extraction is not chemically inert, and the products of interaction of N-metylpyrrolidone and organic matter of coal are present in the composition of the extracts obtained.