Relationship of coal characteristics determined by pyrolysis/gas chromatography/mass spectrometry and nuclear magnetic resonance to liquefaction reactivity and product composition

Five coals, ranging in rank from subbituminous to high-volatile A bituminous, were examined by ¹³C NMR and flash pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). They were also subjected to liquefaction in batch microautoclave reactors at three sets of conditions: 360 °C for 1 h in pyrene; 425 °C similarly; and temperature-programmed liquefaction for 15 min at 200 °C and 30 min at 425 °C in 9,10-dihydrophenanthrene with a sulfided molybdenum catalyst. Four of the five coals showed good relationships between the structural fragments observed in Py-GC/MS and the dominant compound types in the hexane-soluble products from liquefaction at temperatures ≥400 °C. For example, DECS 12 Pittsburgh seam hvA bituminous coal showed a dominance of alkylnaphthalenes in the pyrogram, and this compound class was also dominant in the gas chromatogram of the hexane solubles. ¹³C NMR showed a relationship of f_a^H to conversion of coal to liquids at 425 °C for 1 h. The combination of ¹³C NMR and Py-GC/MS is useful for determining the probable light reaction products of direct liquefaction. The correlations indicate relationships between the compositions of the light fraction of the liquefaction products and coal structural information. The combined characterization approach described here could be used for screening of a wide suite of candidate feedstocks to winnow a few promising candidates for detailed testing.