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The objective of this program has been to study the chemistry of the components with high boiling points in a direct coal liquefaction recycle solvent and to identify those components which lead to higher overall yields and improved product stability in the initial coal dissolution step of direct coal liquefaction processes. The major conclusions are: -454 C recycle solvent is primarily aromatic hydrocarbons (73%) and contains almost no asphaltenes; +454 C recycle solvent is primarily asphaltenes and aromatic hydrocarbons; recycle solvent also contains aliphatic hydrocarbons, N-containing aromatics and O-containing aromatics; heteroatoms in coal derived materials seem to be grouped by type, i.e. acidic O and basic N and sulfur occur together; under helium a small net amount of hydrogen and more CO and CO/sub 2/ are produced than under hydrogen; under hydrogen the amounts of H/sub 2/S and hydrocarbon gases are increased and a small amount of hydrogen gas is usually consumed; overall coal conversions to THF solubles are improved by adding more -454 C solvent but decreased by adding +454 C solvent; for added fractions of -454 C solvent the pecent conversion to THF solubles increases in the order aromatic hydrocarbons (+7.2) > aliphatic hydrocarbons (+0.8) > no addedmore » solvent (0.0) > N-containing aromatics (-0.9) > O-containing aromatics (-22.1); percent conversion to THF solubles using -454 C solvent with +454 C solvent fractions added decrease in the order aliphatics (+3.7) > aromatic hydrocarbons (+3.0) > no added solvent (0.0) > O-containing aromatics (-9.3) > N-containing aromatics (-13.3); of the +454 C solvent components, aromatic hydrocarbons and aliphatic hydrocarbons are beneficial but total only approx. 25% of the +454 C recycle solvent; and steric effects may be important in determining the effectiveness of the heavier solvent components as liquefaction solvents. 28 references, 25 figures, 31 tables.« less |
