Thiophene conversion in the BIMF process

Аксенов, Д. Г.; Климов, О. В.; Ечевский, Г. В.; Paukshtis, E. A.; Budneva, A. A.

doi:10.1023/b:reac.0000037393.85994.cf

Cited by 7 publications

(3 citation statements)

References 4 publications

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“…The bimolecular cracking process is a newly emerging mechanism which is proposed by Shan, Aksenno, and Chica et al [18,[52][53][54] Fig. 6, the thiophene is almost protonated with the C-H bond length of 1.14 Å. Interestingly, for the complex-TH-1, we found another transition state, TS-TH-2' for the protonation step of thiophene molecule at the C position, with the calculated activation barrier of 96.82 kJ/mol that is higher than that for the TS-TH-2 at the C position (69.89 kJ/mol).…”

Section: Bimolecular Thiophene Cracking Over H-beta Zeolitementioning

confidence: 99%

A theoretical investigation into thiophenic derivative cracking mechanism over acidic and cation-exchanged beta zeolites

Mao

Sun

Pei

2015

Computational and Theoretical Chemistry

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A Two-layer ONIOM study has been carried out to investigate the unimolecular and bimolecular cracking mechanisms of thiophene catalyzed by acidic and metal cation-exchanged (Li + , Na + , K + , Cu + , and Ag +) beta zeolites. The unimolecular cracking reactions of 3,4-dimethylthiophene (3,4-DMT) and benzothiophene (BT) catalyzed by acidic beta zeolite are also calculated. It was found that the rate-determining steps in these two mechanisms are both C-S bond cracking. Furthermore, the activation energy of C-S bond cracking in bimolecular mechanism is lower than that in unimolecular mechanism, indicating that the bimolecular cracking process is more favorable. In addition, although the activation energies of C-S bond cleavage of 3,4-DMT and BT over H-beta zeolite are relatively lower than thiophene, the practical process would be difficult to occur due to still high energy barriers. A close analysis of activation energies over cation-exchanged zeolites suggests that the metal cations do not reduce and contrarily increase their difficulty of thiophene cracking reactions.

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Section: Bimolecular Thiophene Cracking Over H-beta Zeolitementioning

confidence: 99%

A theoretical investigation into thiophenic derivative cracking mechanism over acidic and cation-exchanged beta zeolites

Mao

Sun

Pei

2015

Computational and Theoretical Chemistry

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“…If polymerization between the mercaptan with two double bonds and thiophene happens at β position, Species B is formed. A similar mechanism was recently proposed by Aksenov et al [26] and Chica et al [27,28]. Tawara and co-workers [29] reported that 12.3% Ni/ ZnO was applied as a model catalyst for adsorptive ultradeep HDS (UD-HDS) of kerosene in a stream of H 2 containing 25% CO 2 at 600 K. The experiments results showed that residual sulfur in the treated kerosene was not detectable ( < 0.06 wt-ppm) even after 800 h of operation.…”

Section: Researches On Mechanismmentioning

confidence: 54%

Desulfurization mechanism of FCC gasoline: A review

Zhao

Chen

Gao

et al. 2009

Front. Chem. Eng. China

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This paper reviews the most important developments on the desulfurization mechanism of Fluid Catalytic Cracking (FCC) gasoline. First, the origin of sulfur compounds in FCC gasoline and the current developed desulfurization approaches and technologies are briefly introduced, and then the researches on desulfurization mechanism are summarized from experimental and theoretical perspectives. Further researches on the desulfurization mechanism will lay a foundation for optimizing desulfurization sorbents and technologies.

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“…Bimolecular Thiophene Cracking Mechanism. The bimolecular cracking mechanism has been proposed by Shan, 13 Aksenov, 48 and Chica et al 12,49 As described in Scheme 2, four main steps are involved in the bimolecular mechanism: (1) protonation of thiophene on the acidic sites, (2) dimerization of two thiophene molecules, (3) C−S bond cracking and ring-opening of the dimerized thiophene, and (4) removal of sulfur content. As mentioned above, two adsorption modes, η 1 (S) and η 2 (CC), are obtained for the adsorbed thiophene, complex-TH-1.…”

Section: Resultsmentioning

confidence: 99%

Understanding the Nature of Transition States in the Confined Nanospace of Different Acidic Zeolites on the Desulfurization Mechanism of Thiophene

et al. 2018

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We have presented a two-layer ONIOM study on the unimolecular and bimolecular hydrodesulfurization (HDS) mechanisms of thiophene catalyzed by H-Beta, H-MCM-22, H-ZSM-5, and H-FAU zeolites. The rate-determining step for HDS is the hydrogenation step. The bimolecular desulfurization mechanism is more favorable to occur due to the lower free energy barriers, which is in good accord with experimental observations. Hammond's postulate was validated by analyzing the thermodynamics and geometrical structures of transition states (TSs). The difference charge density (DCD), reduced density gradient (RDG), localized orbital locator (LOL), and Fukui functions were used to understand the nature of the TSs. For the dimerization step of two thiophene molecules, the DCD analysis indicates a dramatic electron transfer from the thiophene fragment to the hydrothiophene fragment in the TS. High LOL values between two α-C atoms of two thiophene rings indicate a strong interaction and a high degree of covalence between these two C atoms. For the step of H 2 S formation, a DCD analysis suggests a clear electron transfer from the H 2 S fragment to the organic carbon chain in the TS; the plots of RDG and LOL indicate a weak interaction between the C atom of the organic chain and the H 2 S fragment. The confined nanospace in zeolite has important stabilization effects on TSs and intermediates. The calculated results suggest that almost all the reaction steps in the unimolecular and bimolecular mechanisms on four zeolites are entropy-decreased processes. The stabilization effect of the ZSM-5 framework mainly originates from the VDW attractive interactions. The classic electrostatic interactions favor the formation of all the TSs on MCM-22. In the bimolecular mechanism, the behaviors of TSs in Beta are contrary to those in ZSM-5; the electrostatic interactions favor the formation of TSs over FAU, but no clear variation trend of VDW interactions is found.

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Thiophene conversion in the BIMF process

Cited by 7 publications

References 4 publications

A theoretical investigation into thiophenic derivative cracking mechanism over acidic and cation-exchanged beta zeolites

A theoretical investigation into thiophenic derivative cracking mechanism over acidic and cation-exchanged beta zeolites

Desulfurization mechanism of FCC gasoline: A review

Understanding the Nature of Transition States in the Confined Nanospace of Different Acidic Zeolites on the Desulfurization Mechanism of Thiophene

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