Effects of hydrogen transfer by exchanged cobalt upon liquefaction of low rank coal

Suzuki, Motoyuki; Ohura, Shin-ichi; Endoh, Risa; Hirano, Koji; Mashimo, Kiyoshi

doi:10.1016/j.fuel.2010.12.002

Cited by 25 publications

(5 citation statements)

References 23 publications

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“…While the exchanged Ba 2+ cations promoted the CLR at low temperatures, but restrained it at high values. Besides, ion-exchanged methods, as an inspiration, have been widely used to enhance direct coal liquefaction by introducing the finely dispersed catalytic cations, such as cobalt and iron [18,19]. For example, the oil yield of the iron-exchanged coal was reported to be higher than those of samples treated by impregnation or physical mixing method [20].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Bai

et al. 2015

Fuel Processing Technology

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Section: Introductionmentioning

confidence: 99%

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Bai

et al. 2015

Fuel Processing Technology

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“…The hydrogen transfer observed from hydrogen donors during fragmentation of coal structures or hydrocarbon molecules sometimes is referred to as hydrogen shuttling without a detailed explanation of the molecular phenomena, − perhaps due to the fact that the exact mechanism has not been completely elucidated. The functioning of hydrogen donor solvents during thermal processes can be analyzed based on the cracking of hydrocarbons by the free radical mechanism.…”

Section: Fundamentalsmentioning

confidence: 99%

Use of Hydrogen Donors for Partial Upgrading of Heavy Petroleum

et al. 2016

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The huge energy required to overcome the high-pressure drop in pipelines due to the high viscosity of heavy crude oils has motivated the development of technologies to improve the flow properties of these heavy hydrocarbons, such as friction reduction, viscosity reduction, and in situ upgrading. It has been reported that a series of H-donors has been used to upgrade heavy oil for their transportation (low viscosity and high API gravity). Virtually any organic compound with a low oxidation potential can serve as a useful hydrogen donor. The low oxidation potential enables the transfer of hydrogen(s) from the donor to the substrate under mild reaction conditions. The choice of donor is based on the nature of the reaction, its availability, and solubility in the reaction medium.

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“…According to conventional coal liquefaction theory, the catalyst promotes the transfer of hydrogen from molecular H 2 to the solvent and then to coal, that is, the solvent acts as the medium for the hydrogen transfer . However, some researchers claim that the transfer of hydrogen from both molecular H 2 and the solvent influences the coal liquefaction. , In the primary liquefaction stage, the coal is thermally decomposed and hydrogenated by hydrogen atoms from the hydrogen donor solvent. The resulting products are thereafter hydrocracked by hydrogen atoms generated by H 2 dissociation on the catalyst surface .…”

Section: Introductionmentioning

confidence: 99%

“…12 However, some researchers claim that the transfer of hydrogen from both molecular H 2 and the solvent influences the coal liquefaction. 13,14 In the primary liquefaction stage, the coal is thermally decomposed and hydrogenated by hydrogen atoms from the hydrogen donor solvent. The resulting products are thereafter hydrocracked by hydrogen atoms generated by H 2 dissociation on the catalyst surface.…”

Section: Introductionmentioning

confidence: 99%

Isotope Labeling to Study the Hydrogen Transfer Route during Lignite Modification in a Subcritical D₂O–CO System

et al. 2020

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The hydrogen transfer reaction is one of the key chemical processes of coal conversion. The elucidation of the hydrogen transfer mechanism is essential for rational control of the properties and distribution of products. This paper is focused on the hydrogen transfer mechanism of lignite modification in a subcritical D2O–CO system. Using Soxhlet extraction, isotope ratio mass spectrometry, 1H nuclear magnetic resonance, and pyrolysis–gas chromatography–mass spectrometry (Py-GCMS), the deuterium transfer routes in deuterated products and their representative structures were studied. The existing form of deuterium in deuterated products was also proposed. The results showed that the subcritical D2O–CO system can generate active deuterium, which combines with the free radical fragments resulting from coal pyrolysis to form three kinds of deuterated products: n-hexane solute (NS-D), benzene solute (BS-D), and tetrahydrofuran solute (TS-D). Deuterium in the three solutes migrates in the order TS-D → BS-D → NS-D. It was observed that the active deuterium is not transferred to the β sites of the solutes but rather to their ar, α,2, α, and γ sites. Py-GCMS detection results showed that the solutes mainly consist of six representative structures, that is, monocyclic and polycyclic aromatics, alkenes, alkanes, alcohols, and esters. In the modification process, deuterium is incorporated into the monocyclic aromatic structures in the aliphatic side chains first and then in the aromatic ring. For the polycyclic aromatic structures, the active deuterium enters the side chain first and then the aromatic ring having that side chain. A small amount of active deuterium can be incorporated into the alkene and alkane structures directly. However, it mainly transfers to such structures indirectly through thermal cracking of deuterium-containing macromolecular aromatic structures. Active deuterium reduces oxygen in the oxygen-containing structures to form OD or DHO, yet it cannot easily enter the aliphatic and aromatic structures linked to the oxygen-containing structures. This research provides a new perspective for the study of hydrogen transfer routes and can serve as a reference for discussing the molecular mechanisms involved in various coal conversion processes.

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Effects of hydrogen transfer by exchanged cobalt upon liquefaction of low rank coal

Cited by 25 publications

References 23 publications

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Use of Hydrogen Donors for Partial Upgrading of Heavy Petroleum

Isotope Labeling to Study the Hydrogen Transfer Route during Lignite Modification in a Subcritical D₂O–CO System

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Effects of hydrogen transfer by exchanged cobalt upon liquefaction of low rank coal

Cited by 25 publications

References 23 publications

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Effect of Ca2+ species with different modes of occurrence on direct liquefaction of a calcium-rich lignite

Use of Hydrogen Donors for Partial Upgrading of Heavy Petroleum

Isotope Labeling to Study the Hydrogen Transfer Route during Lignite Modification in a Subcritical D2O–CO System

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Product

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Isotope Labeling to Study the Hydrogen Transfer Route during Lignite Modification in a Subcritical D₂O–CO System