Dynamic Evolution of Zeolite Framework and Metal-Zeolite Interface

Hu, Zhong-Pan; Han, Jingfeng; Wei, Yingxu; Liu, Zhongmin

doi:10.1021/acscatal.2c01233

Cited by 46 publications

(24 citation statements)

References 162 publications

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“…These advantages should also be reflected in the metallic species-introduced zeolite materials and their applications. This kind of introduction would unconsciously imitate some of the characteristics of enzyme catalysis. , Through the synergistic effect of metallic active sites and the reaction microenvironment, the constructed metal–zeolite catalytic system helps the reactants to be adsorbed, be activated, reach the transition state, and generate products, therefore realizing the catalytic cycle in an optimized reaction pathway in some typical reactions, such as alkane activation with strong potential, which is a necessity for industrial applications. − …”

Section: Introductionmentioning

confidence: 99%

Atomic Insight into the Local Structure and Microenvironment of Isolated Co-Motifs in MFI Zeolite Frameworks for Propane Dehydrogenation

et al. 2022

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Embedding metal species into zeolite frameworks can create framework-bond metal sites in a confined microenvironment. The metals sitting in the specific T sites of zeolites and their crystalline surroundings are both committed to the interaction with the reactant, participation in the activation, and transient state achievement during the whole catalytic process. Herein, we construct isolated Co-motifs into purely siliceous MFI zeolite frameworks (Co-MFI) and reveal the location and microenvironment of the isolated Co active center in the MFI zeolite framework particularly beneficial for propane dehydrogenation (PDH). The isolated Co-motif with the distorted tetrahedral structure ({(SiO)2Co(HO–Si)2}, two Co–O–Si bonds, and two pseudobridging hydroxyls (Co···OH–Si) is located at T1(7) and T3(9) sites of the MFI zeolite. DFT calculations and deuterium-labeling reactions verify that the isolated Co-motif together with the MFI microenvironment collectively promotes the PDH reaction by providing an exclusive microenvironment to preactivate C3H8, polarizing the oxygen in Co–O–Si bonds to accept H* ({(SiO)CoHδ− (Hδ+O–Si)3}), and a scaffold structure to stabilize the C3H7* intermediate. The Co-motif active center in Co-MFI goes through the dynamic evolutions and restoration in electronic states and coordination states in a continuous and repetitive way, which meets the requirements from the series of elementary steps in the PDH catalytic cycle and fulfills the successful catalysis like enzyme catalysis.

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Section: Introductionmentioning

confidence: 99%

Atomic Insight into the Local Structure and Microenvironment of Isolated Co-Motifs in MFI Zeolite Frameworks for Propane Dehydrogenation

et al. 2022

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“…However, in the unsymmetrical microenvironment around the BAS, this topological identity cannot be maintained. As shown in Figures 7c and 9c, carbonium, carbo(2,4) and carbonium, carbo (4,2) are not the same. The difference in two carbonium ions cause the difference in the activation free energies between mode II and mode IV.…”

Section: Thermal Stability and Structural Features Of N-hexane Cracki...mentioning

confidence: 80%

“…The formed chemically stable bridging hydroxyl group, -Al(OH)Si-, is the Brønsted acid site (BAS). 2,3 The threecoordinated oxygen atom endows the BAS the acid-catalyzed reactivity. As one of the most important implications for zeolites, 4,5 catalytic cracking of hydrocarbons by Brønsted acid centers is a key process in the conversion of crude oils to transportation fuels and other high-value chemicals in petrochemical industry.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Insight into Thermal Cracking of n-Hexane in the H-FAU Zeolite

et al. 2022

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To understand catalytic cracking processes of alkanes in the petrochemical industry, the monomolecular cracking mechanism of n-hexane in the H-FAU zeolite has been examined using ab initio molecular dynamics simulations combined with enhanced sampling techniques. It has been found that the adsorption energies of short n-alkanes are linearly correlated with the chain length and contact areas with the zeolite framework, while no such correlation can be applied to the short n-alkenes. High-dimensional free energy landscapes characterizing four cracking modes of n-hexane at three different temperatures have been drawn. The electron transfer in the cracking process was analyzed by quantifying the charge evolution for carbon atoms. The formation of carbonium ions in each cracking mode is found to be the rate-limiting step. At high temperature, free energy differences are nonpositive values, suggesting that the cracking of n-hexane is spontaneous, which is also coincident with the experimental observation. The cracking of the central C–C bond of n-hexane is easier than the cracking of terminal C–C bonds, which is due to the lower free energy barrier. The present work sheds new insights into the cracking process of n-alkanes in the industrially used FAU zeolite catalysts.

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“…12,13 Density functional theory (DFT) has been widely used to study factors affecting catalytic reaction mechanisms, including adsorption configuration, Gibbs reaction energy barrier, reaction transition state, etc. 14–21 Fu et al 22 used DFT for 8T and 48T models with the mGGA-M06-L function to study mono-branched alkanes in HY and HZSM-5 adsorption energies. They concluded that pore confinement was critical to adsorbate stability.…”

Section: Introductionmentioning

confidence: 99%