Liquefaction mechanism of Wandoan coal using tritium and 14C tracer methods

Kabe, Toshiaki; Nitoh, O.; Funatsu, Eiji; Yamamoto, K.

doi:10.1016/0016-2361(87)90177-3

Cited by 18 publications

(4 citation statements)

References 8 publications

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“…A useful method to elucidate the hydrogen transfer mechanism in coal liquefaction is to utilize isotopes, such as deuterium and tritium. − Although a deuterium tracer was effective in tracing reactive sites in coal and coal model compounds, there are few samples that enable quantitative analysis of hydrogen mobility in coal, because of poor solubility of coal products and the difficulty of quantification of the deuterium tracer. − We have already reported that tritium and carbon-14 tracer techniques were effective to trace quantitatively the behavior of hydrogen in coal liquefaction. − In these works, it was shown that the quantitative analysis of hydrogen mobility of coal and coal-related compounds could be given through the hydrogen exchange reactions among coal, gas phase, and solvent as well as the hydrogen addition.…”

Section: Introductionmentioning

confidence: 99%

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

et al. 1997

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To elucidate the effect of H2S and H2O on hydrogen exchange reactions between tetralin and gaseous hydrogen, the reactions of tetralin with tritiated hydrogen in the presence of H2S or H2O were performed under practical coal liquefaction conditions. The amounts of hydrogen exchange between tetralin and tritiated hydrogen were estimated from hydrogen and tritium balance. The conversions of tetralin in the presence and absence of H2S at 400 °C for 300 min were 4.1 and 3.9%, respectively, while the hydrogen exchange ratio (HER) of tetralin remarkably increased from 4.6% to 40.4% in the presence of H2S and reached 71% at 400 °C for 600 min. It was suggested that the hydrogen exchange mechanism of tetralin with hydrogen in the presence of H2S would include a different mechanism from that in the absence of H2S. It was considered that the H2S molecule acted as both an initiating species and an HS• radical and rapidly abstracted and added hydrogen atom reversibly, promoting the hydrogen exchange in both an aromatic ring and a naphthene ring. In addition to the radical mechanism, the electrophilic exchange with a proton formed from hydrogen sulfide was proposed for the hydrogen exchange mechanism. On the other hand, the conversion and HER of tetralin in the presence of H2O at 400 °C for 300 min were 1.7 and 1.3%, respectively. These values were smaller than those in the absence of H2O. It was considered that H2O inhibited the formation of tetralyl radicals and the hydrogen transfer from tritiated hydrogen to tetralyl radicals. The tritium distribution in H2S reached equilibrium at the initial stage of the reaction, and the hydrogen exchange reaction between gaseous hydrogen and H2S rapidly occurred. However, it was estimated that the hydrogen exchange reaction between gaseous hydrogen and H2O was slower than that with H2S.

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Section: Introductionmentioning

confidence: 99%

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

et al. 1997

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“…In these studies, it was found that naphthalene has a significant reactivity in the pyrolysis of coal tar. We have already reported that isotope tracer techniques are effective in tracing the reaction pathways, and we have provided quantitative information. − In the present paper, to trace the behavior of naphthalene in the pyrolysis of coal tar, we have used coal tar containing 14 C-labeled naphthalene. This 14 C tracer method is convenient for elucidating of the reaction mechanism of coal tar pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Naphthalene in Pyrolysis of Coal Tar Using the ¹⁴C Tracer Method

Kabe¹,

Godo²,

Otsuki³

et al. 1997

Energy Fuels

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To trace the behavior of naphthalene in the pyrolysis of coal tar, the pyrolysis of coal tar containing 14 C-labeled naphthalene was carried out at 800-950 °C for 40-50 s. It was found that naphthalene has significant pyrolysis reactivity. The distributions of the radioactivities in compounds with 3-5 rings were 21.6, 30.3, and 18.6% at 800, 900, and 950 °C for 50 s, respectively. Furthermore, the distributions of the recovered radioactivity in THFI at 800, 900, and 950 °C for 50 s were 1.6, 5.3, and 47%, respectively, indicating that about half of the 14 C-naphthalene can be converted into tetrahydrofuran insoluble (THFI) in 50 s at 950 °C. This 14 C tracer method using 14 C-labeled naphthalene is convenient for tracing the reactivity of coal tar and for elucidating the reaction mechanism of coal tar pyrolysis.

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“…On the other hand, since the reactions involved in coal liquefaction include hydrocracking and hydrogenation by molecular hydrogen and donor solvents, a number of attempts have been made to elucidate the mechanism of hydrogen transfer occurring during coal liquefaction in the presence of solvents. − A useful method for clarifying the mechanism of hydrogen transfer in coal liquefaction is to utilize isotopes such as deuterium and tritium tracers. − Recently, the authors have reported that tritium and carbon-14 tracer techniques were effective in quantitatively monitoring the hydrogen during coal liquefaction. − These reports showed that the hydrogen mobility of coal and coal-related compounds could be quantitatively analyzed using the hydrogen exchange reactions occurring between coal, the gas phase, and the solvent, as well as by considering the hydrogen addition reactions.…”

Section: Introductionmentioning

confidence: 99%

“…[28][29][30][31][32][33][34][35] Recently, the authors have reported that tritium and carbon-14 tracer techniques were effective in quantitatively monitoring the hydrogen during coal liquefaction. [36][37][38][39][40][41][42][43] These reports showed that the hydrogen mobility of coal and coal-related compounds could be quantitatively analyzed using the hydrogen exchange reactions occurring between coal, the gas phase, and the solvent, as well as by considering the hydrogen addition reactions. The current study of coal liquefaction using tritium attempted to clarify the reactivities of hydrogen in tetralin and in Taiheiyo coal in the presence of conventional and dispersed iron catalysts (pyrrhotite and Fe-(CO) 5 ) and in the presence of sulfur.…”

Section: Introductionmentioning

confidence: 99%

Elucidation of Mechanism of Coal Liquefaction Using Tritium and ³⁵S Tracer Methods

1997

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The reactivity of hydrogen in tetralin and in Taiheiyo coal in the presence of iron catalysts (pyrrhotite and iron pentacarbonyl (Fe(CO)5)) and sulfur were investigated using tritium and 35S tracer methods under liquefaction conditions. Coal liquefaction was performed for 30 min at an initial pressure of 5.9 MPa and a temperature of 400 °C in the presence of tetralin solvent and tritiated hydrogen, with and without a catalyst and 35S-labeled sulfur. The rate of coal conversion and the tritium distribution in coal were higher when Fe(CO)5 and sulfur were used than were obtained with conventional pyrrhotite. Further, the coal products obtained with the use of Fe(CO)5 and sulfur were lighter than those produced in the presence of added pyrrhotite. The results suggest that the catalyst derived from Fe(CO)5 and sulfur was successfully dispersed in the coal and directly acted on the coal to increase both the rate of coal conversion and the tritium transfer from the gas phase to the coal. The iron catalysts greatly promoted the hydrogen exchange between the gas phase and the tetralin solvent in the absence of coal. Part of the added sulfur participated in the sulfur exchange reaction with the pyrrhotite catalyst. The addition of sulfur increased the amount of hydrogen incorporated into the coal. This suggests that sulfur promoted the formation of tetralyl radicals during the hydrogen transfer from the solvent to the coal.

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Liquefaction mechanism of Wandoan coal using tritium and 14C tracer methods

Cited by 18 publications

References 8 publications

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Reactivity of Naphthalene in Pyrolysis of Coal Tar Using the ¹⁴C Tracer Method

Elucidation of Mechanism of Coal Liquefaction Using Tritium and ³⁵S Tracer Methods

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Liquefaction mechanism of Wandoan coal using tritium and 14C tracer methods

Cited by 18 publications

References 8 publications

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H2S and H2O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H2S and H2O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Reactivity of Naphthalene in Pyrolysis of Coal Tar Using the 14C Tracer Method

Elucidation of Mechanism of Coal Liquefaction Using Tritium and 35S Tracer Methods

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Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Elucidation of Coal Liquefaction Mechanism Using a Tritium Tracer Method. Effect of H₂S and H₂O on Hydrogen Exchange Reaction of Tetralin with Tritiated Molecular Hydrogen

Reactivity of Naphthalene in Pyrolysis of Coal Tar Using the ¹⁴C Tracer Method

Elucidation of Mechanism of Coal Liquefaction Using Tritium and ³⁵S Tracer Methods