Structural Characterization of Some North American Coals

Abstract

The structure of five U.S. coals (three of low rank or sub-bituminous and two of high rank) has been investigated using reactivity criteria and spectroscopic methods. The results suggest that one of the high-rank coals PSOC 831 contains more cross-linking groups within its macromolecular structure than the other high-rank coal DECS 12. These cross-linkages help to explain some previously reported anomalous results resulting from reactions of PSOC 831 with hydrogen in the presence of MoS 2 . The DECS 9 and PSOC 1379 were shown to be typical low-rank coals and gave significant "guest"-derived materials (terpenoid and wax-derived hydrocarbons) from pyrolyses at 320 and 350 °C, and the sub-bituminous coal DECS 6 showed many structural similarities when compared with a range of other sub-bituminous coals from Central Queensland, Australia.

Catalysis in Direct Coal Liquefaction

“…A physically associated coal model was set against the molecular/macromolecular model. Evidence to date suggests that the molecular/macromolecular model might apply to lignites, brown coals and sub-bituminous coals [55,56], but not so well to bituminous coals. While the debate on these opposite structure models is continuing, new 1 H NMR experiments appear to reveal that a correlation between molecular mobility derived from proton relaxation times and molecular/macromolecular phases is much more complicated than previously thought [52,53].…”

“…There coal is regarded as a mono-phase of associated macromolecules with average molar masses in the order of a few thousand g mol −1 and a network structure is held together mainly by non-covalent bonds, which include ionic forces, hydrogen bonding, charge-transfer and aromatic π -π interactions [10,[47][48][49][50][51]. The average molecular size and the cross-linking in bituminous coals seem to decrease with increasing rank to a minimum at around 86% carbon [55][56][57]. Moreover, the characterization of solvent-swollen coal by proton spin diffusion and small-angle neutron scattering indicated that part of the volume expansion in solvent swelling is related to a formation of nanoscalic phase-separated domains, and this micro-heterogeneity makes the application of statistical mechanical theories to the swelling of coal dubious [54].…”

Solvent Extraction of Bituminous Coals Using Light Cycle Oil: Characterization of Diaromatic Products in Liquids

“…Direct liquefaction has been shown to be a potential process route to make coal-derived JP-900 . In the liquefaction research, we evaluated Pittsburgh and Blind Canyon coals structurally to determine the relationship of the coal structure to the types of products produced. − Both coals showed good conversions in direct liquefaction experiments. − Blind Canyon was one of the coals tested that had the highest conversions, while Pittsburgh coal conversions were typically a little lower than Blind Canyon. − However, direct liquefaction of these coals produced liquids of very different character. − Hexane-soluble liquids from Blind Canyon coal contained one- and two-ring aromatics as well as long-chain alkanes (up to C 32 ); while hexane-solubles from Pittsburgh coal were mainly two-ring compounds, an attractive characteristic for thermally stable jet fuel once the liquid was hydrogenated. − However, there were issues with using direct liquefaction. The previous research was done using pure solvents, that is, phenanthrene, dihydrophenanthrene, and pyrene. − Another constraint was that long construction times and high capital costs for a grass-roots liquefaction plant made it prudent to examine the possibility of incorporating coal, or coal-derived materials, into existing oil refinery operations.…”