New insight into the chemical structures of Huadian kerogen with supercritical ethanolysis: Cleavage of weak bonds to small molecular compounds

Liu, Qing; Hou, Yucui; Wu, Weize; Wang, Qian; Ren, Shuhang; Liu, Qingya

doi:10.1016/j.fuproc.2018.03.029

Cited by 19 publications

(11 citation statements)

References 38 publications

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“…Previous reports have shown that the reaction temperature was the critical influencing factor for the ethanolysis reaction. , In this work, the ethanolysis experiment was conducted at different temperatures from 320 to 380 °C, and the corresponding conversion was shown in Figure . From Figure , it can be seen that the conversion of Naomaohu coal starts to increase significantly from 320 to 360 °C, then the rise speed slows from 360 to 370 °C.…”

Section: Resultsmentioning

confidence: 99%

“…Supercritical alcoholysis is a type of chemical method that can effectively depolymerize some weak bonds in the organic matter of coal or fossil fuel under mild reaction conditions. ,− For example, Li et al reported that the maximum yield of the ethanol-soluble portion (ESP) of Zhaotong lignite ethanolysis was 64.9% at 305 °C, and the ESP included esters, alcohols, acids, and some other compounds, which can reflect the structural characteristics of Zhaotong lignite . Liu et al conducted the supercritical ethanolysis of Huadian kerogen and found that 87.4% of organic matter was converted at 375 °C by breaking the weak bonds to small molecular compounds (SMCs), including aliphatic acid esters, aliphatic acids, and other compounds, which can deduce the original structure of Huadian kerogen . Fan et al analyzed the ethanolysis products of Dongming lignite and found that supercritical ethanol could not only depolymerize the macromolecular structure of coal but also induce the release of O- and N-containing compounds via hydrogen-bond disruption, alcoholysis, and alkylation …”

Section: Introductionmentioning

confidence: 99%

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New Insights into the Primary Reaction Products of Naomaohu Coal via Breaking Weak Bonds with Supercritical Ethanolysis

Liang

Hou

et al. 2019

Energy Fuels

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Coal is an important energy source in the world, and its chemical structure is the basis of its application, especially for its pyrolysis and liquefaction. Supercritical ethanolysis is a type of chemical extraction that can effectively depolymerize some weak bonds in organic matter. In this work, new insights into the primary products of Naomaohu coal were studied with supercritical ethanolysis. The non-covalent and weak covalent bonds (such as ether and ester bonds) in the coal were broken to yield small molecular compounds (SMCs) with a conversion of 70.3% (dry and ash-free basis) at 370 °C. SMCs, including esters, alcohols, aldehydes, ethers, ketones, hydrocarbons (aromatic and aliphatic hydrocarbons), acids, phenols, and heteroatom compounds, were identified quantitively through gas chromatography/mass spectrometry. Fourier transform infrared spectroscopy and 13C nuclear magnetic resonance were used to characterize the structure of the coal and its ethanolysis residues. The structure characteristic of the coal was deduced through analyzing the SMCs and residues. Interestingly, the SMCs can reflect the primary reaction products of the coal during its pyrolysis or liquefaction.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New Insights into the Primary Reaction Products of Naomaohu Coal via Breaking Weak Bonds with Supercritical Ethanolysis

Liang

Hou

et al. 2019

Energy Fuels

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“…All the above spectral characterization is in accordance with the lignin structure reported. However, the aromatic bridgehead carbon at 126.7 ppm is noteworthy, which is found in coal and oil shale, 37,38 but it has never been reported in lignin. Traditionally, aromatic bridgehead carbon means the existence of polycyclic aromatics.…”

Section: Methodsmentioning

confidence: 95%

Polycyclic Aromatics Observed in Enzymatic Lignin by Spectral Characterization and Ruthenium Ion-Catalyzed Oxidation

Wang

Hou

et al. 2021

J. Agric. Food Chem.

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It is generally considered that lignin is a three-dimensional amorphous polymer consisting of methoxylated phenylpropane structures. However, high yields of monomer structural units of lignin cannot be obtained through various ways, which inspired us to gain insights into the structures of lignin. Herein, enzymatic lignin (EL) was directly characterized by a solid-state 13C nuclear magnetic resonance spectrometer and Fourier transform infrared spectrometer and then subjected to ruthenium ion-catalyzed oxidation. According to the spectral characterization, it can be inferred that multi-ring aromatic clusters exist in EL because of the aromatic bridgehead carbon ratio of 0.136. Based on the results of ruthenium ion-catalyzed oxidation of the EL, it can be deduced that (1) double- and triple-aromatic ring clusters exist in the EL besides the traditional phenylpropane single-aromatic ring clusters, and (2) some aromatic rings with long-alkyl chain substituents exist in the EL, which is quite different from the traditional cognition of lignin. This investigation provides a new insight into the structure of EL.

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“…Substantial effort has been exerted in kerogen studies over the last 2 decades. Previous reports on the chemical composition and structural characteristics of kerogen have indicated that this matter is a complex organic macromolecule with a three-dimensional heterogeneous structure containing aliphatic and aromatic chains with ether, ester, and hydrogen bonds, − which hamper the clarification of kerogen pyrolysis characteristics and result in the diversity of cleavage and rearrangement of various chemical bonds throughout the pyrolysis procedure. , The main reactions in the initial pyrolysis stage of kerogen are the reintegration of macromolecular structure and breakup of oxygen-bridged bonds. The structure of aliphatic carbons contributes to the main components of shale oil, and the content of aromatic carbons results in the yield of char. − , A deep understanding of the kerogen structure is crucial in investigating the pyrolysis characteristic and kinetic mechanism of oil and gas products. − Moreover, kerogens with various chemical compositions and microstructures from different deposits with individual geological origins considerably vary hydrocarbon generation ability. ,− ,, Further discussion on the thermal conversion behaviors of kerogens in different oil shales based on their chemical structural characteristics is necessary.…”

Section: Introductionmentioning

confidence: 99%

Thermal Degradations and Processes of Four Kerogens via Thermogravimetric–Fourier-Transform Infrared: Pyrolysis Performances, Products, and Kinetics

et al. 2020

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The thermal upgrading of kerogen into fuels has scientific and industrial importance in oil shale utilization. In this study, multiple methods were applied to clarify the pyrolysis behaviors of four kerogens from the Huadian (HD) Basin, Fushun (FS) Basin, Luozigou (LZG) Basin, and Dachanggou (DCG) Basin oil shales. Two model-free isoconversional methods and a master plot were utilized to evaluate the kinetic parameters, and the Coats–Redfern method was used to verify the estimated kinetic results. The results indicated that all studied oil shales had very good hydrocarbon generation potential. HD, FS, and LZG oil shales could be described as type I kerogen, whereas DCG oil shale was type II1 kerogen with high aromatic content. HD kerogen featured a stronger polarity and contained more aliphatic structures compared with the three other samples, which induced the mass loss of its first stage at ∼38%, even larger than that of its second pyrolysis stage; the activation energies of the main pyrolysis stage of HD kerogen could also be divided clearly into two stages and in accordance with the thermogravimetric results. The thermal cracking processes of these FS, LZG, and DCG kerogens were mainly concentrated in the second pyrolysis stage, and the activation energies of FS and LZG kerogens did not show a considerable variation with conversion degrees. Moreover, DCG kerogen possessed the largest amount of aromatic structures which resulted in high yields of char, and the activation energies of the main pyrolysis stage of DCG kerogen was almost the largest, especially when the conversation rate was above 0.7. Evolution behaviors of oil and gas products at different temperatures during pyrolysis were related to the cleavage of chemical bonds in kerogen. CH4 and light C2+ aliphatic hydrocarbons were the typical gaseous products released from the main reaction stages of all four kerogens, and the evolving behavior of each typical gaseous product of four kerogens featured good similarity. The results showed that aliphatic and aromatic carbon contents in kerogen had a remarkable effect on its thermal characteristic and kinetic parameters, and the saturated aliphatic bonds and oxygen-containing bonds were easy to crack and had potentially low activation energy of reaction compared with those of aromatic bonds. Results of the master plot and Coats–Redfern methods verified that the Avrami–Erofeev kinetic model was the optimal model for the pyrolysis of the studied kerogens, thereby indicating that the four kerogens evolved under a similar genetic condition.

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New insight into the chemical structures of Huadian kerogen with supercritical ethanolysis: Cleavage of weak bonds to small molecular compounds

Cited by 19 publications

References 38 publications

New Insights into the Primary Reaction Products of Naomaohu Coal via Breaking Weak Bonds with Supercritical Ethanolysis

New Insights into the Primary Reaction Products of Naomaohu Coal via Breaking Weak Bonds with Supercritical Ethanolysis

Polycyclic Aromatics Observed in Enzymatic Lignin by Spectral Characterization and Ruthenium Ion-Catalyzed Oxidation

Thermal Degradations and Processes of Four Kerogens via Thermogravimetric–Fourier-Transform Infrared: Pyrolysis Performances, Products, and Kinetics

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