An ab initio study of ethane conversion reactions on zeolites using the complete basis set composite energy method

Zheng, Xiaobo; Blowers, Paul

doi:10.1016/j.molcata.2004.11.009

Cited by 35 publications

(28 citation statements)

References 62 publications

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“…This method has been used for many zeolite investigations [12,18,32]. The Brönsted acid cluster model used in this work is presented in Fig.…”

Section: The Acidity Effect On the Initiating Stage Of Mo-ethylidene mentioning

confidence: 99%

“…However, as far as the experiments are concerned it is difficult to give a comprehensive understanding of the mechanism on how the acidity acts on heterogeneous olefin metathesis. Theoretical calculations have been not only used to predict the zeolite acidity but also to the catalytic reaction since it can reveal the interaction of reactant with the acid site and the reaction transition state formed on the surface [12]. In the present study, density functional theory (DFT) calculations are performed on the Mo/HBeta catalyst with different acidity.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Support Acidity on Olefin Metathesis over Heterogeneous Mo/HBeta Catalyst: A DFT Study

Zheng

Guan

et al. 2010

Catal Lett

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The effect of support acidity on the crossmetathesis of ethylene and 2-butylene to propylene over heterogeneous Mo/HBeta catalyst was studied by density functional theory (DFT) calculations. The zeolite acidity was mimicked by changing the terminating Si-H bond lengths. Both of the initiating formation and propagating processes of Mo-carbene were investigated. It is found that there is a correlation between the zeolite acidity and the activation barrier. The influence of acidity on the initial Mo-carbene formation process is greater than that on the next process catalyzed by this active site. Theoretical calculations reveal that the heterogeneous catalyst with more acidic support could have better olefin metathesis activities, which is consistent with the experimental findings in the literature.

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“…This method has been used for many zeolite investigations [12,18,32]. The Brönsted acid cluster model used in this work is presented in Fig.…”

Section: The Acidity Effect On the Initiating Stage Of Mo-ethylidene mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Support Acidity on Olefin Metathesis over Heterogeneous Mo/HBeta Catalyst: A DFT Study

Zheng

Guan

et al. 2010

Catal Lett

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“…Zheng and Blowers 19,36,39 studied the effects of the proton acidity on the hydrocarbon cracking reaction barriers with the 3T cluster. Blaszkowski et al 40 inves- Figure 5 The pathways of the n-butane monomolecular dehydrogenation reaction on the acidic zeolites: (a) primary dehydrogenation reaction and (b) secondary dehydrogenation eaction.…”

Section: Acid Effectmentioning

confidence: 99%

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

2008

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Density functional theory was used to study monomolecular cracking reaction of n-butane on acidic zeolite. Geometry optimizations of the local structures of the species reacting with the zeolite were carried out by using the 5T cluster model at the B3LYP/6-311＋G(3df,2p)//B3LYP/6-31G(d) level. In this work, the deprotonation modes of two different order C atoms in n-butane cracking on H-ZSM-5 were explored in detail by the density functional theory. The calculated activation barriers at the B3LYP/6-311＋G(3df,2p)//B3LYP/6-31G(d) level are 238 kJ/mol for the primary C-C cracking, 217 kJ/mol for the secondary C-C cracking, 296 kJ/mol for the primary dehydrogenation, and 242 kJ/mol for the secondary dehydrogenation, respectively. The difference of the activation barrier is 54 kJ/mol for the deprotonation reactions of two different order C atoms in n-butane. For the dehydrogenation reaction, the results indicate that the reaction is expected to be preferred at the secondary C atom. Additionally, the relation between the acidity and structure of the cluster shows that the acidity effect of the zeolite can be simulated by modifying the peripheral bonds of the cluster for the 5T cluster. Finally, the zeolite acidity effects on the reaction barriers were investigated by changing the cluster terminal Si-H bond length.

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“…Again, the calculated activation energies for all alkanes were very similar, with the largest difference being 6 kJ/mol. In a series of papers, Zheng et al [35][36][37][38] published studies on proton exchange for the same series of short alkanes as considered in this study. Structures were optimized using the B3LYP method, and energies were calculated using the CBS-QB3 composite energy method, providing complete basis set (CBS) total energy estimates.…”

Section: Potential Energy For Stationary Pointsmentioning

confidence: 99%

“…Esteves et al [33] Ryder et al [34] Zheng and Blowers [35][36][37][38] Level of theory B3LYP/6-31G* MP2/6-31G* BH&HLYP/6-31++G** B3LYP/6-31G*, CBS-QB3 significant trends in the activation energies in the series of short alkanes. Thus, at first sight, the theoretical results seem to be in disagreement with the experimental results.…”

Section: Potential Energy For Stationary Pointsmentioning

confidence: 99%

Proton exchange of small hydrocarbons over acidic chabazite: Ab initio study of entropic effects

Bučko

Benco

Häfner

et al. 2007

Journal of Catalysis

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An ab initio study of ethane conversion reactions on zeolites using the complete basis set composite energy method

Cited by 35 publications

References 62 publications

The Effect of Support Acidity on Olefin Metathesis over Heterogeneous Mo/HBeta Catalyst: A DFT Study

The Effect of Support Acidity on Olefin Metathesis over Heterogeneous Mo/HBeta Catalyst: A DFT Study

n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study

Proton exchange of small hydrocarbons over acidic chabazite: Ab initio study of entropic effects

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