Theoretical investigation of the mechanism of ethanol to propene catalyzed by phosphorus-modified FAU zeolite

Tong, Qiaoxian; Xia, Mengya; Sun, Huai; Sun, Yi; Han, Sheng; Li, Qianggen

doi:10.1007/s00214-022-02911-8

Cited by 3 publications

(7 citation statements)

References 45 publications

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“…The QM and MM energy values are listed in Table 1. In our previous theoretical work, 18,23,28,42 the negative MM energy contributions in the ONIOM free energy barriers indicate that the zeolite framework is favorable for the formation of TS structures and the positive MM energy values are unfavorable for the stability of TS structures. In Table 1, two remarks could be obtained.…”

Section: Resultsmentioning

confidence: 89%

“…35,38−41 The UFF force field developed by Rappe et al is often used to describe the nonbonded interactions in the zeolitic catalytic reactions. 28,42,43 In order to save computational time, we divided the 18 T QM region into two parts, an active 12 T subregion treated with the 6-31g(d,p) basis set and an inactive 6 T subregion treated with the 3-21G basis set. The 12 T QM subregion includes all the reactants and the catalytic center of zeolite; bond formation or breaking steps occur in this region.…”

Section: Computational Modeling and Methodsmentioning

confidence: 99%

“…44 This optimization strategy is validated in many previous theoretical works. 28,42,43 We further performed single point energy calculations on the 18 T QM region by using the larger basis sets, 6-311+G(2df,2p) and 6-31G(d,p) on the 12 and 6 T subregion atoms, respectively. The experimental temperatures in the industrial MTP process often vary between 250 and 400 °C.…”

Section: Computational Modeling and Methodsmentioning

confidence: 99%

“…The Bro̷nsted acid site is then formed by adding one acid proton (H) directly to the bridging oxygen atom (O1 position) bonded to the Ga atom. Finally, the terminal Si atoms in the Ga-FAU model are saturated by the Si–H bonds with a fixed bond length of 1.47 Å. , The DFT method with M06-2X functional and universal force field (UFF) is employed to describe the QM and MM atoms, respectively. − It is well-known that the M06-2X functional developed by Zhao et al could accurately predict the thermochemistry, noncovalent interactions, electronic excitation energies, and aromatic–aromatic stacking interactions of main-group elements. ,− The UFF force field developed by Rappe et al is often used to describe the nonbonded interactions in the zeolitic catalytic reactions. ,, …”

Section: Computational Modeling and Methodsmentioning

confidence: 99%

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Methanol to Propene over Gallium-Modified FAU Zeolite: Theoretical Study on the Polymethylbenzene and Alkene Cycles

Miao,

Sun,

Han

et al. 2024

J. Phys. Chem. C

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The catalytic performance of gallium-modified acidic FAU (Ga-FAU) zeolite in the methanol to propene (MTP) process was theoretically investigated by a two-layer ONIOM (our own N-layered integrated molecular orbital and molecular Mechanics) method. The whole MTP mechanism includes two cycles: the polymethylbenzene (polyMB) cycle and the alkene cycle. The polyMB cycle consists of the direct internal H-shift pathway, spiro pathway, methyl-transfer pathway, and paring pathway. Compared with the previous theoretical results on the MTP process on the pure acidic Si/Al FAU, the addition of Ga atoms into the Si/Al H-FAU could reduce the contribution of the polyMB cycle and increase the reactivity of the alkene cycle on the MTP process. A careful analysis of activation free energy barriers on the transition states (TSs) shows that the internal H-shift step is the ratedetermining step for the direct internal H-shift pathway and the paring pathway. The ratedetermining step for the spiro and methyl-transfer pathways is the methylation of the PMB molecule. The methylation of the propene molecule is the rate-determining step for the alkene cycle. The polyMB and alkene cycles have almost the same reactivity on the Ga-FAU zeolite. For the polyMB cycle, the different elementary steps are in the following order of reactivity: internal methyl transfer > deprotonation > C−C bond cracking > ring contraction > methylation > internal H-shift. The order in the alkene cycle is different: deprotonation > proton transfer > beta-scission > methylation. The differential charge density (DCD), local orbital locator (LOL), and reduced density gradient (RDG) revealed the direction of electron flow in different fragments in the TS structures and the nature of interactions between the fragments in the TSs.

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Section: Resultsmentioning

confidence: 89%

Section: Computational Modeling and Methodsmentioning

confidence: 99%

Section: Computational Modeling and Methodsmentioning

confidence: 99%

Section: Computational Modeling and Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Methanol to Propene over Gallium-Modified FAU Zeolite: Theoretical Study on the Polymethylbenzene and Alkene Cycles

Miao,

Sun,

Han

et al. 2024

J. Phys. Chem. C

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“…They reported that the tertiary carbenium ions are more stable than tert-alkoxides. In our previous study 50,69 on the ethanol to propene (ETP) on phosphorus-modified FAU zeolite and acidic Si/Al ZSM-5 and FAU zeolites, two C their respective conformers of tertiary carbenium ions. In the present study, INT-I-6 is a C 6 intermediate (2-methyl-2pentoxide).…”

Section: Mtb Reaction Pathway Inmentioning

confidence: 99%

Comprehensive Theoretical Investigation of the Mechanism of Methanol to Aromatics Catalyzed by Gallium-Modified FAU Zeolite

Xia,

Sun,

Han

et al. 2023

J. Phys. Chem. C

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The catalytic transformation of methanol to aromatics (MTA) over gallium-modified zeolites has been widely developed as an important technology to produce aromatics such as benzene, toluene, and xylene (BTX) in the petrochemical industry. However, the reaction mechanisms of the MTA process at the atomic level remain unclear but are valuable to experimentally design more efficient catalysts. In this study, the MTA mechanisms on gallium-modified acidic FAU (Ga-FAU) zeolite have been theoretically investigated by a two-layer our Own N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) method. The MTA process includes methanol to benzene (MTB) and methylation of benzene to hexamethylbenzene (BTH). Their rate-determining steps are the intermolecular proton transfer of cyclohexene for MTB and the methylation step of methylbenzene for BTH. The different elementary steps in the MTB pathway could occur in the following order of reactivity: deprotonation ≥ intramolecular proton transfer > cyclization > intramolecular CH 3 shift > methylation > intermolecular proton transfer. In BTH, the deprotonation step is more favorable than the methylation step. In the MTB pathway, the deprotonation, intramolecular proton transfer, and CH 3 -shift steps are generally entropy-increased, but the cyclization, methylation, and intermolecular proton transfer steps are entropy-decreased. All elementary steps in the BTH pathway are entropy-decreased. Overall, MTB and BTH have almost the same reactivity on the Ga-FAU zeolite. The entire MTA reaction proceeds in the direction of reducing free energies. Differential charge density maps (DCD), local orbital localization maps (LOL), and reduction density gradient maps (RDG) reveal the nature of transition states (TSs) from the viewpoint of electron migration and explain the complicated attractive and repulsive interactions between different molecular fragments in TSs. The wave function analysis suggests that spatial hindrance and van der Waals (VDW) attractive forces generally coexist in the TS fragments. There are clear partial covalent interactions and moderate VDW interactions between the atoms in the forming/breaking chemical bonds.

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Catalytic Study for Linear Olefin Formation from Ethanol over Phosphorus-modified Beta-Zeolite Catalysts

Hadi

2024

Preprint

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In this study, we explore the catalytic performance of phosphorus-modified Beta zeolite catalysts for the selective conversion of ethanol to linear olefins, to understand the effects of phosphorus incorporation on the structural, textural, acidic, and hydrophobic properties of the zeolite catalysts, we employed various characterization techniques, such as XRD, N2 physisorption, NH3-TPD, and TGA, the phosphorus-modified Beta zeolites demonstrated enhanced selectivity towards C4-C12 linear olefins, with the P/Beta-5 catalyst (containing 5 wt.% phosphorus) achieving an impressive 72% combined selectivity, we attribute this improved catalytic performance to the moderation of acid site strength and density, as well as the increased hydrophobicity induced by phosphorus modification, these properties effectively suppressed undesired side reactions and promoted the formation of linear olefins through the oligomerization-cracking pathway, we systematically investigated the influence of phosphorus loading and modification method on the catalytic activity, revealing important structure-activity relationships. Based on our experimental findings, we propose a reaction mechanism that highlights the basic role of phosphorus in modulating the reaction pathways, the results of this study give us valuable insights into the design and optimization of phosphorus-modified zeolite catalysts for the efficient and desired production of linear olefins from bio-derived ethanol.

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Theoretical investigation of the mechanism of ethanol to propene catalyzed by phosphorus-modified FAU zeolite

Cited by 3 publications

References 45 publications

Methanol to Propene over Gallium-Modified FAU Zeolite: Theoretical Study on the Polymethylbenzene and Alkene Cycles

Methanol to Propene over Gallium-Modified FAU Zeolite: Theoretical Study on the Polymethylbenzene and Alkene Cycles

Comprehensive Theoretical Investigation of the Mechanism of Methanol to Aromatics Catalyzed by Gallium-Modified FAU Zeolite

Catalytic Study for Linear Olefin Formation from Ethanol over Phosphorus-modified Beta-Zeolite Catalysts

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