Cluster quantum-chemical study of the chemisorption of methane on a lithium-promoted magnesium oxide doped by zinc oxide

N. U. Zhanpeisov, M. Baerns

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

The reaction of a methane molecule with a lithium-doped magnesium oxide catalyst ( Li MgO) containing small amounts of Zn2+ cations (Zn/Li/MgO) was theoretically studied using a modified MINDO/3 method and applying a supermolecular approach. The surface of magnesium oxide (MgO) was modelled by a Mg32O32 four-layer molecular cluster containing all types of structural defects i.e., low-coordinated magnesium and oxygen ions (Mg2+LC and O2-LC) of various faces, edges, corners etc. Molecular clusters of lithium-promoted magnesia ( Li MgO) were simulated by isomorphic substitution of Mg2+LC by Li+LC; the excess negative charge of the cluster was compensated by a proton connected to an O2-3C site. For Zn-doped Li MgO or MgO an isomorphic substitution of Mg2+LC by Zn2+LC was assumed. The calculations indicate that for Zn/Li/MgO or Zn MgO the substitution of a threefold coordinated magnesium cation by zinc is more favourable by energetics than for four- and five-fold coordinated Mg cations. The computational results are used to interpret the experimentally observed increase of C2+ hydrocarbons selectivity in the oxidative coupling of methane when doping a NaOH-promoted CaO catalyst with minor amounts of Zn2+ cations.

Original languageEnglish
Pages (from-to)139-142
Number of pages4
JournalJournal of Molecular Catalysis. A, Chemical
Volume99
Issue number3
DOIs
Publication statusPublished - 1995 Jul 3
Externally publishedYes

Keywords

  • Chemisorption
  • Lithium-promoted magnesium oxide
  • Magnesium oxide
  • Methane
  • Quantum-chemical study
  • Zinc oxide

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

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