Heterocompounds present in asphaltenes from various products of coal hydrogenation

Abstract

The asphaltenes from hydrogenated coal extract (product A) as well as from hydrogenated low-temperature coal tars (products B and C) obtained from three bituminous coals were investigated. The asphaltenes were separated into basic (B) and acidic/neutral (A/N) fractions by precipitation of HCl adducts of nitrogen bases. The B and A/N fractions were investigated by means of thin-layer chromatography and i.r. spectroscopy to assist functional-group detection. Moreover, their high-resolution and field-ionization mass spectra were determined. The molecular weights of the asphaltene fractions are in the 80–600 amu range, and a few hundred molecular peaks were observed on the FIMS spectra. Part of the components were identified by HRMS — 27 nitrogen-compound types were found in the B fractions, while 38 compound types of O, N and S were detected in the A/N fractions. Although the asphaltenes were derived from two different liquefaction processes of three different coals, no significant differences in their composition have been found. They are hydrogenbonded complexes of basic and acidic components that are essentially the same heterocompounds in products A, B and C.