Partial Oxidation of Methane on the SiO2 Surface-A Quantum Chemical Study
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- 作者：Sukru Ozturk ; Isik Onal ; and Selim Senkan
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2000
- 出版时间：February 2000
- 年：2000
- 卷：39
- 期：2
- 页码：250 - 258
- 全文大小：364K
- 年卷期：v.39,no.2(February 2000)
- ISSN：1520-5045
文摘
Reaction pathways for methane partial oxidation (MPO) on silica were theoretically investigatedusing the semiempirical MOPAC-PM3 molecular orbital method. The surface of SiO2 was modeledby 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- and4-coordinated Si surface atoms. Calculated bond dissociation energies for Si-H, SiO-H, andSi-OH were comparable to H-CH3, H-OH, and O-O. In the second phase, elementary reactionsaround the bridge structure were studied.The facile ring-opening reaction with water, whichreconstitutes a pair of vicinal hydroxyls, was found both thermodynamically and kineticallyfavored, in good agreement with the experiment and other theoretical methods. Activation ofmethane by the lattice bridge oxygen was thermodynamically unfavorable with high activationenergy. On the other hand, the computational results also confirmed the important role adsorbedor "activated" oxygen plays in an MPO reaction, and indicated the likely formation of methanolas an intermediate in formaldehyde production.