Carboncarbon cleavage during asphaltene formation

Collins, Clair J.; Raaen, Vernon F.; Benjamin, Ben M.; Kabalka, George W.

doi:10.1016/0016-2361(77)90051-5

Cited by 37 publications

(10 citation statements)

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“…The foregoing shows that reaction of BPE in supercritical methanol led to equimolar formation of toluene and phenol. This is similar to previous reactions in tetralin (Collins, 1977;Korobkov et al, 1988a,b;Sat0 and Yamakawa, 1985), which suggests that methanol was a hydrogen donor. This motivated the reaction of BPE in fully deuterated (CD,OD) supercritical methanol.…”

Section: Resultssupporting

confidence: 90%

“…In this work, we studied similar mechanistic possibilities through reaction of the BPA analogue, BPE, whose thermal chemistry has been thoroughly studied (Schlosberg et al, 1981a(Schlosberg et al, ,b, 1983Virk, 1979;Frederick and Bell, 1984a,b;Mobley and Bell, 1979;Gilbert, 1984;King andStock, 1982, 1984;Larsen and Lee, 1983;Takemura et al, 1981;Collins et al, 1977;Matsuhashi et al, 1985;Korobkov et al, 1988a,b;Sato and Yamakawa, 1985;Stein, 1981) and therefore provided a convenient background to explore solvent effects.…”

Section: Introductionmentioning

confidence: 99%

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The Benzylphenylether thermolysis mechanism: Insights from phase behavior

Klein

Sandler

1990

AIChE Journal

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The thermolysis of benzylphenylether (BPE) was examined at 320°C in liquid, vapor, and supercritical methanol phases as a probe of the reaction mechanism. Toluene and phenol were the major products in all cases, but observed selectivities were dependent upon the reaction phase. Isotopic labeling experiments demonstrated that methanol participated in the reaction network as a hydrogen donor through a free-radical mechanism. These results are consistent with free-radical steps for neat BPE primary pyrolysis that include BPE fission followed by hydrogen abstraction and radical recombination reactions. A detailed set of 2 1 free-radical steps quantitatively explains the dependence of the selectivity and conversion on the phase behavior. Introduction Supercritical fluid (SCF) solvents represent interesting and potentially powerful tools for reaction engineering because of their extreme P-V-T behavior near their critical point. As reaction media, SCF solvent properties can potentially be optimized via adjustments of pressure to improve reaction rates and selectivities. As we show here, SCF solvents can also be useful in the interpretation of kinetic information in the probe of reaction mechanisms. BenjaminReported supercritical solvent effects include electrostatic interactions (Townsend et al., 1988;Johnston and Haynes, 1987), diffusional limitations (Lawson and Klein, 1985;Abraham, 1987;Helling and Tester, 1987;Yang and Eckert, 1988), and pressure effects (Johnston and Haynes, 1987;Simmons and Mason, 1972). However, the thermodynamic phase behavior can also affect global reaction kinetics and lead to interesting apparent solvent effects.The reaction of dibenzylether (DBE) in supercritical toluene provides an example of the influence of phase behavior on laboratory kinetics information. The conversion of DBE after 30 min at 375°C and constant initial DBE concentration, [DBE],, dropped from 90% at 5 atm to 50% at 48 atm, where the pressure increase was generated through the addition of toluene. Interpretation of the data by assuming a single-phase pressure effect would suggest an apparent activation volume of 2,000 cm3/mol, as much as three orders of magnitude greater Correspondence concerning this ppcr rhould he addrcsscd to M. T. Klein. than typical intrinsic activation volumes (le Noble, 1978).However, phase equilibrium calculations showed the existence of a two-phase region that explained the drop in conversion without recourse to pressure-dependent rate constants.Thus the adjustment of the pressure can also control the number and composition of phases in which a reaction occurs. This presents the opportunity to highlight the various elementary steps of a complex reaction mechanism since the concentrations of species can be varied easily by over two orders of magnitude by changing from the liquid to the vapor phase. This allows emphasis of, and discrimination between, unimolecular and bimolecular steps and their influence on global kinetics and selectivities. This is the object of the present paper, where we descr...

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

The Benzylphenylether thermolysis mechanism: Insights from phase behavior

Klein

Sandler

1990

AIChE Journal

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“…7 Benzophenone has been used but at 400 °C, and we feared this high temperature would alter the coal. 8 More recently, a variety of aromatic molecules have been used as dehydrogenation agents. 9,10 They are effective and the results are interesting, but it is difficult to monitor the extent to which they may become incorporated into the coal.…”

mentioning

confidence: 99%

Measuring the Hydrogen Donor Reactivity and Capacity of Coals

Larsen

Nomura

1998

Energy Fuels

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“…Bibenzyl (BB) has been commonly chosen as the model compound to represent the typical C aliphatic -C aliphatic weak bond in coal. Thermolysis of BB in gas and liquid phases has been extensively investigated [5][6][7][8], and the results have been reviewed by Marvin L. Poutsma [9]. It is generally accepted that the homolytic cleavage of C aliphatic -C aliphatic bond to form benzyl radicals is the primary process, and toluene was the primary product when there was no catalyst, while stilbene was the primary product when CaO was used as catalyst [8].…”

Section: Introductionmentioning

confidence: 99%