Synchronous fluorimetric characterization of heavy intermediates of coal direct liquefaction

In order to understand the molecular structure of coal and the mechanism of coal direct liquefaction, the heavy intermediates of coal liquefaction such as asphaltene (AS) and preasphaltene (PA) were separated into different sub-fractions by column chromatography, respectively. The distributions of fused aromatic nucleuses (FAN) of sub-fractions were determined by synchronous fluorescence combined with the fitting technique of multiple peaks of spectrum. The results indicated that the PA and AS obtained from liquefactions of three Chinese coals were separated into 4 and 2–4 sub-fractions, respectively. The content of three rings FAN was the highest in the major sub-fractions of AS. The major sub-fractions of PA contained not only more single ring aromatic nucleus but also larger FAN than those of AS. Meanwhile, there were more complex aggregations in PA compared to AS.

► Three-rings aromatics are the most abundant in the major sub-fraction of asphaltenes.
► Preasphaltenes have more 1-ring aromatics and larger aromatics than asphaltenes.
► There were more complex aggregations in preasphaltenes compared to asphaltenes.