Partial oxidation of methane on the SiO2 surface - A quantum chemical study

Date

2000-02-01

Author

Ozturk, S
Onal, I
Senkan, S

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

200
views

0
downloads

Reaction pathways for methane partial oxidation (MPO) on silica were theoretically investigated using the semiempirical MOPAC-PM3 molecular orbital method. The surface of SiO2 was modeled by a helical Si6O18H12 molecular cluster that also exhibits a strained siloxane bridge defect. First, a bond energy analysis was performed on the silica cluster with isolated 3- and 4-coordinated Si surface atoms. Calculated bond dissociation energies for Si-H, SiO-H, and SI-OH were comparable to H-CH3, H-OH, and O-O. In the second phase, elementary reactions around the bridge structure were studied. The facile ring-opening reaction with water, which reconstitutes a pair of vicinal hydroxyls, was found both thermodynamically and kinetically favored, in good agreement with the experiment and other theoretical methods. Activation of methane by the lattice bridge oxygen was thermodynamically unfavorable with high activation energy. On the other hand, the computational results also confirmed the important role adsorbed or "activated" oxygen plays in an MPO reaction, and indicated the likely formation of methanol as an intermediate in formaldehyde production.

Subject Keywords

V2o5/tio2 systems, Working mechanism, Electron correlation, Semiempirical methods, Active-sites, Oxide catalysts, Selective oxidation, Dehydroxylated silica, Silica-supported moo3, AB-initio calculations

URI

https://hdl.handle.net/11511/66428

Journal

INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH

DOI

https://doi.org/10.1021/ie990252c

Collections

Department of Chemical Engineering, Article

Suggestions

OpenMETU
Core

Quantum chemical study of the catalytic oxidative coupling of methane Onal, I; Senkan, S (1997-10-01) Oxidative coupling of methane reaction pathways on MgO and lithium-modified MgO were theoretically studied using the semiempirical MNDO-PM3 molecular orbital method. The surface of the MgO catalyst was modeled by a Mg9O9 molecular cluster containing structural defects such as edges and corners. Lithium-promoted magnesia was simulated by isomorphic substitution of Mg2+ by Li+; the excess negative charge of the cluster was compensated by a proton connected to a neighboring O2- site. Heterolytic adsorption of ...
Direct Methane Oxidation to Methanol by N2O on Fe- and Co-ZSM-5 Clusters with and without Water: A Density Functional Theory Study Fellah, Mehmet Ferdi; Önal, Işık (2010-02-25) Density functional theory (DFT) calculations were carried Out ill a Study of oxidation of methane to methanol by N2O on the Fe- and Co-ZSM-5 clusters. The catalytic cycle steps have been Studied oil model Clusters ((SiH3)(4)AlO4M) (where M = Fe, Co). Calculations indicate very low methanol selectivity Without water and increasing rate of methanol formation with water. These results are in qualitative agreement with the experimental literature. The methanol formation step is also found to be the rate-limitin...
DFT investigation of high temperature water gas shift reaction on chromium-iron mixed oxide catalyst Yalcin, Ozgen; Önal, Işık (2014-11-20) As part of high temperature water gas shift reaction mechanism, CO adsorption and H2O adsorption on Fe3O4 (111) and chromium atom substituted Fe3O4 (111) slab surfaces are investigated by means of periodic DFT approach using VASP. Fe3O4 bulk structure has been computed including the Hubbard (U) parameter. One oxygen site (Ooct1) is studied as a probable site among the six Fe3O4 (111) terminations. Cr atom substitution on this surface is also examined. Cr atoms prefer being on the surface rather than in the ...
Epoxidation of Propylene on a [Ag14O9] Cluster Representing Ag2O (001) Surface: A Density Functional Theory Study Fellah, Mehmet Ferdi; Önal, Işık (2012-01-01) Density functional theory calculations were employed to study partial oxidation of propylene on a [Ag14O9] cluster representing Ag2O (001) surface for which positive effect for ethylene oxide formation has been reported in our earlier work at the same level of theory (Fellah et al., Catal Lett 141: 762, 2011). Propylene oxide (PO), propanal, acetone and G-allyl radical formation reaction mechanisms were investigated. P-allyl formation path and two propylene adsorption paths resulting in PO formation are com...
Ethylene and acetaldehyde production by selective oxidation of ethanol using mesoporous V-MCM-41 catalysts Gucbilmez, Yesim; Doğu, Timur; Balci, Suna (2006-05-10) Vanadium-incorporated MCM-41 type catalytic materials, which were synthesized by a direct hydrothermal synthesis procedure, showed very high activity and high selectivity in the production of ethylene from ethanol in an oxidative process. Ethylene selectivity showed a significant increase with an increase in temperature over 300 degrees C, while relatively high acetaldehyde selectivities were observed at lower temperatures. An ethylene yield value of 0.66 obtained at 400 degrees C with an O-2/ethanol feed r...

Citation Formats

S. Ozturk, I. Onal, and S. Senkan, “Partial oxidation of methane on the SiO2 surface - A quantum chemical study,” INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, pp. 250–258, 2000, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/66428.