Mechanism of hydrogen transfer and role of solvent during heating-up stage of direct coal liquefaction

Niu, Ben; Jin, Lijun; Li, Yang; Shi, Zhiwei; Li, Yueting; Hu, Haoquan

doi:10.1016/j.fuproc.2017.02.026

Cited by 44 publications

(20 citation statements)

References 32 publications

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“…In this regard, a transfer of four atoms of hydrogen may be achieved by complete dehydrogenation of a tetralin molecule (Figure a), while the complete dehydrogenation of the saturated form of the monomer in SHTA renders 26 atoms of hydrogen (Figure b). In line with the function of hydrogen donor disclosed in the present study, various authors have consistently observed lowering of the amount of coke in thermal cracking of hydrocarbons when using hydrogen donors, − which is a consequence of the decrease of free-radical concentration yielding a slowdown of polymerization reactions that produce coke.…”

Section: Resultssupporting

confidence: 88%

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

et al. 2020

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A novel solid hydrogen transfer agent (SHTA) based on an organic polymer containing fused-aromatic-ring units, supported in an inorganic matrix, was prepared and tested as a hydrogen donor in the upgrading of a heavy crude oil and its 274 and 343 °C+ residua. The SHTA performance is compared with that obtained using a conventional liquid hydrogen donor (tetralin). Three sets of experiments were carried out in a batch reactor: (1) hydrovisbreaking (HVB), (2) HVB with added tetralin, and (3) HVB with added SHTA. The results showed that the use of tetralin or SHTA in the HVB reaction enhances upgrading of heavy oils compared with the experiments without a hydrogen donor (HVB alone). Moreover, lower coke formation and a higher yield of liquid products were observed. The results obtained when using the novel SHTA are equivalent to those obtained when using tetralin as a hydrogen donor in the upgrading of a heavy crude oil and its 274 and 343 °C+ residua.

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Section: Resultssupporting

confidence: 88%

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

et al. 2020

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“…As the pressure increases, the content of S gradually increases, and M 2 has almost twice the S content as the SF coal. In this case, S is added as a cocatalyst and generates a catalytically active phase Fe 1‐x S. The sulfur‐rich pyrrhotite surface has a large number of iron vacancies that can adsorb active hydrogen, stabilize free radicals, and promote the decomposition of some organic functional groups, such as ether bonds, resulting in an increase in the oil yield and coal conversion …”

Section: Resultsmentioning

confidence: 99%

Significantly enhances caking index of long‐flame coal under tetralin‐glycerol/H₂ system

Liu

Wang

Yang

et al. 2019

Asia-Pacific J Chem Eng

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For alleviating of the shortage of coking coal resource and efficient cleaning and utilization of low-rank coal, hydro-plasticization of low-rank coal was carried out. However, the caking property of low-rank coal cannot be obviously improved under mild conditions in the traditional tetralin-H 2 system. This study is to investigate the feasibility of mixed tetralin-glycerol as a solvent in the process of low-rank coal hydro-plasticization. The solvent ratios of tetralin-glycerol, reaction pressure, and atmosphere were varied to evaluate their effects on hydro-plasticization. The results show that the caking index (G RI ) of long-flame coal increases from 0 to 78 at mild conditions, and the hydrogen transfer mechanism might be directly from H 2 to coal rather than through hydrogen-donor solvents in the mixed solvent case. The solvent extraction and the G RI of modified coals were measured and found that the G RI of modified coal has a good linear relationship with PAA yield, and its R 2 is .985.

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“…15 However, other researchers believe that the main hydrogen transfer route in the liquefaction process is from molecular H 2 to coal directly. 17 The solvent serves only to ensure the solubility of coal 18 and may even hinder the hydrogenation of coal by H 2 because of competitive adsorption on coal. 19 On the other hand, the catalyst can selectively activate not only different forms of hydrogen but also the hydrogenation sites on coal.…”

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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Mechanism of hydrogen transfer and role of solvent during heating-up stage of direct coal liquefaction

Cited by 44 publications

References 32 publications

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

Significantly enhances caking index of long‐flame coal under tetralin‐glycerol/H₂ system

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

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Mechanism of hydrogen transfer and role of solvent during heating-up stage of direct coal liquefaction

Cited by 44 publications

References 32 publications

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

Batch Reactor Study for Partial Upgrading of a Heavy Oil with a Novel Solid Hydrogen Transfer Agent

Significantly enhances caking index of long‐flame coal under tetralin‐glycerol/H2 system

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

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Significantly enhances caking index of long‐flame coal under tetralin‐glycerol/H₂ system

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