Bridging and terminal hydroxyls. A structural chemical and quantum chemical discussion

Mortier, Wilfried; Sauer, Joachim; Lercher, Johannes A.; Noller, H.

doi:10.1021/j150649a016

Cited by 165 publications

(65 citation statements)

References 4 publications

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“…In the case of the isolated 54T cluster, the calculated stretching frequency of the acidic H−O bond is 3623 cm . 13,[38][39][40] Besides, the optimized geometric data of the 54T cluster were found to be in general agreement with the previous computational results concerning H-ZSM-5 36,37 and those of the crystal structure of H-ZSM-5 found in XRD study. 41 Therefore, it is a good justification to use the 54T model to represent a real ZSM-5 zeolite.…”

Section: Models and Computational Methodssupporting

confidence: 89%

Zeolite-catalyzed Isomerization of 1-Hexene to trans-2-Hexene: An ONIOM Study

Li¹,

Zhu²,

Liu³

et al. 2011

Bulletin of the Korean Chemical Society

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Details of the double-bond isomerization of 1-hexene over H-ZSM-5 were clarified using density functional theory. It is found that the reaction proceeds by a mechanism which involves the Brønsted acid part of the zeolite solely. According to this mechanism, 1-hexene is first physically adsorbed on the acidic site, and then, the acidic proton transfers to one carbon atom of the double bond, while the other carbon atom of the double bond bonds with the Brønsted host oxygen, yielding a stable alkoxy intermediate. Thereafter, the Brønsted host oxygen abstracts a hydrogen atom from the C 6 H 13 fragment and the C-O bond is broken, restoring the acidic site and yielding trans-2-hexene. The calculated activation barrier is 12.65 kcal/mol, which is in good agreement with the experimental value. These results well explain the energetic aspects during the course of double-bond isomerization and extend the understanding of the nature of the zeolite active sites.

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Section: Models and Computational Methodssupporting

confidence: 89%

Zeolite-catalyzed Isomerization of 1-Hexene to trans-2-Hexene: An ONIOM Study

Li¹,

Zhu²,

Liu³

et al. 2011

Bulletin of the Korean Chemical Society

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“…From Table 1, it is evident that the ratio of observed to theoretical frequencies, Oobs/0th .... is approximately constant for the 3-21G** basis set. Thus, calculated frequencies may be scaled by this ratio (Mortier et al 1984;Sauer 1989) in order to facilitate comparison with experimental results. Because we are mainly interested in shifts of the OH stretch from the molecular H20 value, all theoretical OH stretching frequencies presented below have been scaled by a factor of 0.93 to correct for discre- pancies between experimental spectra and our theoretical results.…”

Section: Comparison Of Theoretical and Experimental Vibrational Spectmentioning

confidence: 99%

Calculated trends of oh infrared stretching vibrations with composition and structure in aluminosilicate molecules

1993

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Abstract. Ab initio, molecular orbital calculations have been performed on a variety of hypothetical aluminosilicate molecules to investigate relationships among composition, structure, and infrared spectra of OH. Vibrational analyses of the full-optimized molecular geometries at the 3-21G** level were performed with Gaussian 92 to determine theoretical infrared spectra. Theoretical infrared OH frequencies, ~(OH), shift 10 to 100 cm -1 with ionic substitutions. The inverse correlation of theoretical infrared OH intensities with OH stretching frequencies in these aluminosilicate molecules is similar to that observed for aluminosilicate glasses

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“…A detailed discussion based on nonempirical calculations of the structure and properties of hydroxyl groups in zeolites and silica is given in Ref. 29. Electronic excitation energies were measured to establish the different bonding states of aluminium in zeolites [30].…”

Section: What Do We Expect From Quantum Chemical and Statistical-thermentioning

confidence: 99%

Quantum chemical studies on zeolites and silica

Sauer

Zahradník

1984

Int J of Quantum Chemistry

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After mentioning differences in C-0 and Si-0 bonding and different structural types of silicates, the conclusion that interactions between external partners and surfaces of silica and zeolites are mostly dominated by van der Waals forces is discussed. Consequently, the theoretical treatment includes (i) selection of appropriate cluster models, (ii) application of nonernpirical quantum chemical methods for obtaining interaction potentials, and (iii) statistical thermodynamic evaluation of adsorption characteristics. As examples vibrational frequencies of H,O and NH3 adsorbed on cationic sites, the interaction of conjugated hydrocarbons with Na+ sites, and the interaction of H 2 0 with various sites on silica and zeolite surfaces are considered.

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Bridging and terminal hydroxyls. A structural chemical and quantum chemical discussion

Cited by 165 publications

References 4 publications

Zeolite-catalyzed Isomerization of 1-Hexene to trans-2-Hexene: An ONIOM Study

Zeolite-catalyzed Isomerization of 1-Hexene to trans-2-Hexene: An ONIOM Study

Calculated trends of oh infrared stretching vibrations with composition and structure in aluminosilicate molecules

Quantum chemical studies on zeolites and silica

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