Structural aspects of sub-bituminous coal deduced from solvation studies. 2. Hydrophenanthrene solvents

Ruberto, Raffaele G.; Cronauer, Donald C.; Jewell, D.M.; Seshadri, K. S.

doi:10.1016/0016-2361(77)90037-0

Cited by 46 publications

(22 citation statements)

References 7 publications

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“…The hydrogenation of phenanthrene proceeds stepwise leading predominantly to the sym-octahydro stage rather than the asymmetrical form (Ruberto et al, 1977). The hydrogenation of phenanthrene proceeds stepwise leading predominantly to the sym-octahydro stage rather than the asymmetrical form (Ruberto et al, 1977).…”

Section: Methodsmentioning

confidence: 99%

Isomerization and Adduction of Hydrogen Donor Solvents under Conditions of Coal Liquefaction

Cronauer¹,

Jewell²,

Shah³

et al. 1979

Ind. Eng. Chem. Fund.

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Hydroaromatic structures are recognized as "ideal" for liquefying coal due to their ability to readily transfer hydrogen to free radical acceptors. While hydroaromatic hydrogens are preferred, substituted aromatic solvents can compete although the latter are more likely to polymerize or adduct with the acceptors. Hydroaromatic structures rearrange to isomeric forms of enhanced stability which are less likely to transfer hydrogen. Six-membered hydroaromatics such as tetralins and octahydrophenanthrenes contract to fivemembered rings (methylindans, etc.). This isomerization is dependent upon temperature, reactor residence time, and, in particular, the level of acceptor radicals. At relatively low temperatures (300-425 OC), the isomerization process is preceded by the adduction of the original hydroaromatic donor with very stable acceptor molecules. This adduction appears to increase with high organic oxygen and sulfur structures. While rearrangements of the above type have been qualitatively known for several years, the present study has attempted to delineate both the kinetic and structural aspects involved.Periodic or semibatch operation of a continuous stirred reactor produces levels of mixing on the macroscale which are intermediate to the limits of plug flow and stirred tank operation and which can be selected and controlled to any desired level. Such a scheme is an operational alternative to the tanks-in-series or plug flow with recycle system, and provides a means of experimentally producing a desired mixing level or of increasing the yield of desired intermediates in complex reaction schemes. In this work criteria for obtaining desired mixing levels are presented, the resulting degree of segregation, J, is derived, and the influence of segregation or conversion for a second-order reaction is presented. Comparisons to the more familiar tanks-in-series and recycle-plug-flow models are included.

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Section: Methodsmentioning

confidence: 99%

Isomerization and Adduction of Hydrogen Donor Solvents under Conditions of Coal Liquefaction

Cronauer¹,

Jewell²,

Shah³

et al. 1979

Ind. Eng. Chem. Fund.

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“…Therefore, it appears that the physical solvent abilities of BLT coal in phenanthrene, pyrene, and fluoranthene are better than that in tetralin. Meanwhile, phenanthrene, pyrene, and fluoranthene can pick up hydrogen atoms from the hydrogen-donor solvent to produce 9,10-dihydrophenanthrene (2HPN), 4,5-dihydropyrene (2HPy), and 4HFL, respectively, which are known to be more reactive hydrogen donors than tetralin. − The addition of decalin, 1-methylnaphthalene, naphthalene, or anthracene to tetralin failed to provide a better coal conversion and oil yield. The solubility parameter, δ, of decalin is 9.0 (cal/cm 3 ) 1/2 , which is lower than those of PAHs.…”

Section: Resultsmentioning

confidence: 99%

“…Some non-hydrogen-donor polycyclic aromatic hydrocarbons (PAHs), which might be contained in the recycled solvent of the DCL process, can abstract hydrogen atoms from hydrogen donors (H 2 and hydrogen-donor solvent) or by transfer of a labile hydrogen from coal and form, in situ, a new hydrogen donor with a higher hydrogen-donating ability. − Ruberto et al concluded that hydrogenated phenanthrene is an excellent solvent as a hydrogen donor and transfer agent in the presence of a cobalt molybdate-type liquefaction catalyst. Chiba et al reported that mixtures of fluorene or pyrene and tetralin can shuttle hydrogen efficiently.…”

Section: Introductionmentioning

confidence: 99%

Interaction between Hydrogen-Donor and Nondonor Solvents in Direct Liquefaction of Bulianta Coal

Niu

Jin

et al. 2016

Energy Fuels

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Solvent plays two very important roles in coal liquefaction: (1) Physically, it serves as a medium for coal transport and heat transfer, and (2) chemically, it serves as an important source of transferable hydrogen (hydrogen donor) and hydrogen shuttle between hydrogen and coal. In this work, eight types of non-hydrogen-donor solvents, namely, decalin, 1-methylnaphthalene, naphthalene, fluorene, anthracene, phenanthrene, pyrene, and fluoranthene, were examined in combination with the hydrogen-donor solvent tetralin in the liquefaction of Bulianta coal to clarify the interactions between the hydrogen-donor and non-hydrogen-donor solvents and the mechanism of hydrogen transfer. In the absence of a catalyst, the mixed solvents of tetralin with phenanthrene, pyrene, and fluoranthene showed favorable effects on coal conversion and oil yield compared with pure tetralin, regardless of whether the reactions were conducted in a H2 or N2 atmosphere. The reactions of non-hydrogen-donor solvents with tetralin showed that phenanthrene, pyrene, and fluoranthene can pick up hydrogen atoms from the donor to produce 9,10-dihydrophenanthrene, 4,5-dihydropyrene, and 1,2,3,10b-tetrahydrofluoranthene, respectively, which are known to be more reactive hydrogen donors than tetralin. In the presence of nanosized iron catalyst, the addition of phenanthrene, pyrene, or fluoranthene to tetralin was found to improve the liquefaction performance in a N2 atmosphere, whereas in a H2 atmosphere, almost the same coal conversion and oil yield were obtained for all types of mixed solvents. This suggests that the transfer mechanisms of hydrogen are different in the cases of N2 and H2 atmospheres in the presence of nanosized iron catalyst; that is, the primary hydrogen-transfer mechanism might be directly from H2 to coal rather than through hydrogen-donor solvents.

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“…Nishioka and Larson, in a follow-up to the work of Larson and Mohammadi 18 have shown that London dispersion forces increase in importance as rank increases 19 due to an increase in the concentration of aromatic units. Covalent bridges are believed to consist predominately of ether linkages 20 and methylene bridges. 21,22 Ignasiak and Gawlak estimates that roughly half of all covalent cross-links might be ether linkages.…”

Section: Using Polymers To Model the Structure Of Coalmentioning

confidence: 99%

Molecular Accessibility in Oxidized and Dried Coals

Kispert¹

1999

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Changes in physical and chemical structure of the micropore system in eight solvent swelled Argonne Premium Coal Sample (APCS) coals upon weathering were studied using the EPR spin probe method. Spin probes, which are allowed to diffuse into the coal structure during swelling, are trapped when the swelling solvent is removed. Excess spin probes are removed from the coal surface and larger pores so that only the presence of spin probes trapped in pores which closely approximate the size of the spin probe are detected. Detailed explanations and illustrations of the experimental procedure used are given.Careful examination of the weathering process on coal as a function of rank was accomplished using the EPR spin probe method. The retention of spin probes in eight APCS coals provided valuable insight into both the loss of water and the oxidation which occur during the weathering process. The results could be explained in terms of the autoxidation process observed in other polymeric systems. It was shown that initial oxidation of coal can result in increased cross-linking in the coal structure. As the oxidation process continued, both the covalent and hydrogen bonded character of the coal were significantly altered. The retention character of some coals during oxidation was shown to change by as much as three orders of magnitude. Experiments were performed to study the effects of short term oxidation and dehydration on coal structure by exposing the coal samples to argon or oxygen for time periods up to five minutes. The results indicate that the structure of coal is extremely sensitive to environmental changes and exhibits significant changes in as little as 30 seconds. Exposure of Illinois #6 coal to argon or oxygen for 30 seconds caused a decrease in the retention of polar spin probes by as much as an order of magnitude.The studies presented here suggest that the structure of coal is dynamic in nature, and has an intimate relationship with the nature of its environment. This method has been shown to be very sensitive to structural changes brought about in coal by oxidation and dehydration, and can be used to follow changes in coal during the swelling process. Additional ideas for future studies using the EPR spin probe method are also discussed.iv

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Structural aspects of sub-bituminous coal deduced from solvation studies. 2. Hydrophenanthrene solvents

Cited by 46 publications

References 7 publications

Isomerization and Adduction of Hydrogen Donor Solvents under Conditions of Coal Liquefaction

Isomerization and Adduction of Hydrogen Donor Solvents under Conditions of Coal Liquefaction

Interaction between Hydrogen-Donor and Nondonor Solvents in Direct Liquefaction of Bulianta Coal

Molecular Accessibility in Oxidized and Dried Coals

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