Abstract Producing transportation fuels from coal involves multistep conversion of coal to liquids, and then refining of the liquids to fuels. Liquids obtained from direct conversion of coal have properties similar to that of coal from which it was generated. These properties differ from those of crude oil-derived fuels. Formulating a strategy to refine coal liquids to on-specification fuels requires understanding the molecular composition of coal liquid and it differences from on-specification fuels.The coal liquids were prepared by direct liquefaction of lignite coal in a batch autoclave reactor.  The conversion was performed at 415 �C under 4 MPa H2 pressure using coal tar distillate as solvent (coal to solvent ratios 1:2).  After 1 hour the reactor was cooled to 100 �C and coal liquid was separated from solid residue by filtration. The liquid products was distilled into four different fractions with boiling point ranges 120-250, 250-300, 300-343 and 343-370 �C. Different analytical techniques were employed for characterization. Coal-derived liquids were characterised with low hydrogen content (H/C ratios 0.7-1.0), as well as high nitrogen content (3867-10,047 ppm). GC-MS showed Carbazole as the major nitrogen-containing compound in 300-343 oC fraction. NMR, GC-MS and HPLC analysis revealed the highly aromatic nature of the coal-derived liquids. Aromatic carbon content ranged from 80-93 wt%. The 120-250 oC fraction consisted predominantly of two ring aromatic compounds, while four ring compounds dominated the 343-370 �C fraction.High nitrogen content of coal liquids poses a challenge to acid catalysed refining. Given the highly aromatic nature of coal liquids, a high octane aromatic gasoline blend can be obtained by naphtha reforming. Whilst hydrogenation may be sufficient to produce on-specification jet fuel, it is insufficient for on-specification diesel fuel. Therefore, selective hydrogenolysis might be required. Keywords: Lignite coal, liquefaction, NMR, GC-MS, HPLC, Elemental Analysis, transportation fuels.

Characterization of coal liquids for refining to transportation fuels

246th National Meeting (2013)

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