Unimolecular Pyrolysis Mechanism of Thiophene and Furan: An Ab Initio Comparative Study

Li, Tianshuang; Li, Jie; Hong-liang, Zhang; Wang, Jingkun; Xiao, Jin

doi:10.1021/acs.energyfuels.1c00291

Cited by 7 publications

(7 citation statements)

References 65 publications

(122 reference statements)

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“…Five different dissociation pathways were observed and the results were in agreement with the previous work [19]. Xiao and co-workers [21] have studied the pyrolysis mechanisms of thiophene and furan at B3LYP/cc-pVTZ//CCSD(T)/CBS level of electronic structure theory and found the intramolecular H transfer to be the energetically favored initial dissociation step in agreement with earlier predictions [19]. In the present work, we investigated the high temperature pyrolysis of thiophene using Born-Oppenheimer direct dynamics [22,23] simulations to establish the atomic level mechanisms of the initial decomposition steps of thiophene.…”

Section: Introductionsupporting

confidence: 92%

“…A total of 30 trajectories were computed and no reactivity was observed for the entire integration time. This is due to the innate stability [21] of the thiophene ring and the energy available in the trajectories was insufficient to cause any dissociation. Roughly, 125 and 150 kcal mol −1 of energy was present in the trajectories at temperatures of 2500 and 3500 K temperatures, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Standard processes for sulfur removal such as hydrodesulfurization are not effective for thiophene and its derivatives due to innate stability associated with these compounds [12]. To this end, several experimental and theoretical studies have been performed to understand the thermal decomposition pathways of thiophene molecule [13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Theoretical studies of unimolecular decomposition of thiophene at high temperatures

Naz¹,

Paranjothy²

2021

Electron. Struct.

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Thiophene is an organo-sulfur aromatic molecule present in fossil fuels and alternate fuels such as shale oils and contributes to air pollution via fuel burning. Hence, it is essential to remove thiophene and its derivatives during the refining process. In this regard, experimental and electronic structure theory studies investigating the thermal decomposition of thiophene have been reported in the literature. In the present work, high temperature thermal decomposition of thiophene was investigated using Born–Oppenheimer direct dynamics simulations. The trajectory integrations were performed on-the-fly at the density functional B3LYP/6-31+G* level of electronic structure theory to investigate the atomic level decomposition mechanisms. Simulation results show that C–S cleavage accompanied by an intramolecular proton transfer to C is the dominant initial dissociation step. Acetylene was observed as primary decomposition product and the results are in agreement with previous experimental studies.

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Section: Introductionsupporting

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Theoretical studies of unimolecular decomposition of thiophene at high temperatures

Naz¹,

Paranjothy²

2021

Electron. Struct.

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“…The decomposition of thiophene is generally initialed by hydrogen transfer or C–S homolysis. ,, There are three modes of initial reactions, denoted as modes A–C (Figure a), corresponding to the homolysis of C2–S1, the C2-to-S1 hydrogen transfer, and the C3-to-C2 hydrogen transfer. The energy barriers are 322.5, 360.6, and 299.2 kJ/mol.…”

Section: Resultsmentioning

confidence: 99%

“…The results indicated that, albeit the distinct structure of thiophene-S, H 2 S is the preferred S-containing product, with respect to COS and SO 2 . Considering the decomposition mechanism of thiophene, it is generally believed that the reaction is initialed by hydrogen transfer or homolysis. ,, Li et al considered that 1,2-hydrogen transfer is most likely for the initial decomposition of thiophene, while only the formation of CS radical was studied. The homolysis of the C–S bond can also lead to the opening of the thiophene, , and the formed radical fragments (e.g., S, SH, and CS radicals) further interact with functional groups or radicals to generate S-containing gases. ,,, …”

Section: Introductionmentioning

confidence: 99%

Formation of Sulfur Species from Thiophene Decomposition and the Impact of Alkali Metal Ions: A Density Functional Theory Study

Liu,

Xia,

Sun

et al. 2024

Energy Fuels

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Pyrolysis is an efficient utilization method for Scontaining organic solid wastes to produce value-added chemicals and fuels but is accompanied by gaseous pollutants (e.g., H 2 S and COS). The selective transformation of sulfur to H 2 S in the pyrolysis gas will be beneficial for the quality improvement of liquid and solid products, as well as the further management of sulfur. However, the S-containing gas formation mechanism, especially the influence mechanism of widely presented alkali metals, is still unclear. Herein, the formation pathways of Scontaining radicals/gases (S, SH, CS radicals, and H 2 S) was investigated by combining density functional theory (DFT), kinetic calculations, and wave function analysis with thiophene as the model compound. The impact of K + and Na + on Scontaining species formation was carefully studied to elucidate the enrichment method for H 2 S. Thiophene decomposition is preferentially initialized by the 1,2-hydrogen transfer reaction. The formation competitiveness of S-containing species is in the order SH radical ≈ H 2 S > CS radical ≈ S radical, indicating the dominance of H 2 S compared with those of COS and CS 2 formed through CS radicals. Alkali metal ions can enhance the decomposition of thiophene and are beneficial to the direct formation of H 2 S and S radicals through enhanced hydrogen transfer reactions. An inferior generation path of SH radicals is significantly enhanced, and the CS radical formation is inhibited in the presence of K + and Na + . Consequently, alkali metal ions are conducive to direct and indirect generation and enrichment of H 2 S in the gas phase. The elucidation of the enhanced H 2 S formation method can lay a theoretical basis for the waste-to-value utilization of H 2 S in the pyrolysis gas.

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Theoretical Study on the Dissociation Mechanism of Thiophene in the UV Photoabsorption, Ionization, and Electron Attachment Processes

Upadhyaya

2024

Int J of Quantum Chemistry

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A computational study on the intricate mechanism of thiophene ring‐fragmentation (TRF) in the UV photodissociation, dissociative ionization, and dissociative electron attachment process has been performed. The complete fragmentation process is studied using high level G4 composite method for neutral, cationic, and anionic species by elucidating a detailed mechanism for various reaction channels. The study shows that for neutral thiophene, the major pathway is the migration of H atom and subsequent fragmentation through a transition state yielding acetylene (HC≡CH) and H2C=C=S. However, for the thiophene cation, the acetylene (HC≡CH)+H2C=C=S+ channel is a two‐step and barrier less process. The onset of CH3+HC=C=C=S channel has been observed in both the thiophene cation and anion which was absent in the neutral analogue. Similarly, the onset of H2S+HC≡C—C≡CH channel has been found to operate only in the thiophene cation. Others, such as HCS and HS elimination channels have been found in all the species showing similar dissociation mechanism. For the thiophene anion, the TRF process is very much similar to that of thiophene cation. However, the reaction enthalpies of the various elimination channels in the anionic species are lower as compared to that of cationic species. During the study, the ionization energies and electron affinities of various molecules/radicals produced during the fragmentation process of thiophene were also computed.

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Unimolecular Pyrolysis Mechanism of Thiophene and Furan: An Ab Initio Comparative Study

Cited by 7 publications

References 65 publications

Theoretical studies of unimolecular decomposition of thiophene at high temperatures

Theoretical studies of unimolecular decomposition of thiophene at high temperatures

Formation of Sulfur Species from Thiophene Decomposition and the Impact of Alkali Metal Ions: A Density Functional Theory Study

Theoretical Study on the Dissociation Mechanism of Thiophene in the UV Photoabsorption, Ionization, and Electron Attachment Processes

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