Isomerization and adduction of hydrogen donor solvents under conditions of coal liquefaction
Numerous implications on the fundamental chemistry of coal liquefaction can be drawn from the observed reaction of solvent isomerization and adduction. The literature indicated that recycle solvents from most coal liquefaction processes consist of 2 to 3 aromatic rings with various degrees of saturation, not unlike the model solvents studied. In this system, high levels of effective hydrogen donors can rearrange to isomers having poor donor quality. The following specific points were noted: (1) The isomerization of hydroaromatic donor solvents was a general phenomenon. (2) The rate of rearrangement appeared to be first order with respect to donor solvent concentration. (The activation energy of the tetralin reaction was in the range of 26 to 32 Kcal/g-mole, depending upon whether a free radical precursor is present or not.) (3) The rate of isomerization increased with increasing number of hydroaromatic rings. (4) The rate of rearrangement was increased by order of magnitude when free radicals are present. (5) All solvents had the capability of becoming irreversibly adducted by acceptor free radicals which could arise from the coal. (6) The presence of oxygen and sulfur functions on the free radicals enhanced adduction. Adduction was also enhanced by long reaction times and low temperatures (< 400/sup 0/C). (7) At high temperatures (> 400/sup 0/C), adducts were most likely to involve only poor donor solvents; high temperatures would not necessarily cleave adducts formed at low temperatures. (8) Solvent isomerization created a basic problem in following the progress of liquefaction, namely, measuring the amount of transferred hydrogen. While it was possible to measure the level of transferable hydrogen (hydroaromatic six-membered ring hydrogen) in the feed, recycle, or product liquids by /sup 13/C--NMR (5), the study suggested that it was not possible to isolate the portion contributing to hydrogen transfer alone.
- Research Organization:
- Gulf Research and Development Co., Pittsburgh, PA
- OSTI ID:
- 5955320
- Report Number(s):
- CONF-790415-P3
- Journal Information:
- Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States), Journal Name: Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States) Vol. 24:2; ISSN ACPCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010405* -- Coal
Lignite
& Peat-- Hydrogenation & Liquefaction
ACTIVATION ENERGY
ADDUCTS
AROMATICS
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
CHEMISTRY
COAL
COAL LIQUEFACTION
CRYOGENIC FLUIDS
ELEMENTS
ENERGY
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
HYDROCARBONS
HYDROGEN
ISOMERIZATION
LIQUEFACTION
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SOLVENTS
OXYGEN
RADICALS
SOLVENTS
SULFUR
TETRALIN
THERMOCHEMICAL PROCESSES