Elucidation of hydrogen mobility in coal under reductive atmosphere using a tritium tracer method

Ishihara, Atsushi; Nishigori, D.; Ohashi, Yoko; Kim, S.; Qian, Weihua; Kabe, Toshiaki

doi:10.1016/s0016-2361(02)00057-1

Cited by 3 publications

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“…It is well-known that the hydrogen in the hydroxyl functional group is easy to exchange. − There are a lot of studies to determine the amount of hydroxyl functional group. − Stock et al suggested that 8 ± 2% of the oxygen atoms are in hindered phenolic compounds and 10 ± 2% are in unhindered phenolic compounds by the analysis of the oxygen atom distribution by O-methylation with methyl- 13 C iodide and nuclear magnetic resonance analysis . On the basis of their results and ultimate analysis of POC, the amount of hydrogen in the hydroxyl functional group is ca.…”

Section: Discussionmentioning

confidence: 99%

“…The amounts of these exchangeable hydrogens should be dependent upon the reaction conditions. We have already reported that possible mechanisms for hydrogen exchange of coal with tritiated gaseous hydrogen in the presence of a catalyst can be considered as shown in Scheme . − , In the presence of the Pt catalyst, the hydrogen in alkyl groups, functional groups with a heteroatom, and aromatics with those functional groups may be related to the hydrogen exchange. In part a (eqs 7 and 8) of Scheme , where toluene is used as a model compound, the benzyl radical is formed in the reaction with the tritium radical (or hydrogen atom).…”

Section: Discussionmentioning

confidence: 99%

“…Recently, the authors reported that the tritium tracer methods are effective to determine hydrogen in the functional group of coal through the reaction of coal with tritiated water in a pulse flow or batch reactor . Further, for hydrogen exchange reactions between coal and tritiated gaseous hydrogen using a flow reactor, a pulse tritiated hydrogen molecule in N 2 carrier gas was activated on a Pt/Al 2 O 3 catalyst to provide hydrogen radicals that exchange with hydrogen in coal without hydrogen addition in the range of 200−300 °C. , Moreover, the apparent hydrogen exchange rate of coal between coal and tritiated gaseous hydrogen in the presence of a Pt/Al 2 O 3 catalyst was estimated . The Pt/Al 2 O 3 catalyst activated the dissociation of molecular tritiated hydrogen even at the lowest temperature studied.…”

Section: Introductionmentioning

confidence: 99%

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Temperature-Programmed Elimination of Tritium in Coal Labeled by Tritiated Gaseous Hydrogen

2009

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The hydrogen exchange of an Argonne Pocahontas #3 (POC) coal with tritiated gaseous hydrogen in the presence of a Pt/Al 2 O 3 catalyst was carried out using a fixed-bed reactor at a temperature range of 200-250 °C. Then, the tritiated coal sample was re-exchanged with hydrogen in a gaseous hydrogen atmosphere at different raising temperature rates. The changes in radioactivity of tritium releasing from the tritium-labeled coal sample in the temperature-programmed elimination (TPE) of tritium was monitored by a radioanalyzer in situ. The release profile of tritium was fit using three Gaussian distribution functions in TPE. On the basis of the waveform analysis, the amounts and activation energies of the hydrogen exchange for every type of exchangeable hydrogen were estimated. The values of exchange activation energies are 8.8 ( 0.5, 10.7 ( 0.5, and 16.3 ( 0.5 kcal/ mol for three types of exchangeable hydrogen, respectively. The amount of type-I hydrogen was independent of the exchange reaction temperature. In contrast to this, the amount of types II and III of exchangeable hydrogen increased with an increasing exchange temperature, suggesting that the amount of types II and III of hydrogen in the coal is dependent upon the exchange temperature.

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