A DFT study on peroxo-complex in titanosilicate catalyst: Hydrogen peroxide activation on titanosilicalite-1 catalyst and reaction mechanisms for catalytic olefin epoxidation and for hydroxylamine formation from ammonia

Hiroaki Munakata, Yasunori Oumi, Akira Miyamoto

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85 Citations (Scopus)

Abstract

Density functional theory calculations were performed on an activation of hydrogen peroxide over a cluster model of a titanosilicate catalyst. The calculation results showed possibility to form the hydrated peroxotitanosilicalite complex, containing a (Ti)-O-O-(Si) peroxo-moiety, as an oxidizing agent. Using this hydrated peroxo-titanosilicalite complex as an oxidizing agent, oxidation mechanisms were postulated for ethene epoxidation and for ammonia oxidation to form hydroxylamine. The ethene molecule was oxidized with the peroxo-oxygen coordinated to the central Ti atom of the hydrated peroxo-titanosilicalite complex, to form ethylene epoxide. For the ammonia oxidation process, ammonia replaced the adsorbed water molecule of the hydrated peroxo-titanosilicalite complex. The oxidation of the adsorbed ammonia in the (ammonia)-peroxotitanosilicalite complex led to the formation of an ammonia-W-oxide complex of the titanosilicalite catalyst model. The (ammonia-N-oxide)-titanosilicalite complex was transformed into the (hydroxylamine)-titanosilicalite complex, with a hydrogen transfer from the nitrogen to the oxygen of the ammonia-W-oxide moiety. The transition states were explored for these reaction processes. Using the peroxo-titanosilicalite complex containing a Ti-O-O-Si peroxo-moiety as an active oxidizing agent, the catalytic reaction mechanisms are proposed for ethene epoxidation and for ammonia oxidation to form hydroxylamine.

Original languageEnglish
Pages (from-to)3493-3501
Number of pages9
JournalJournal of Physical Chemistry B
Volume105
Issue number17
DOIs
Publication statusPublished - 2001 May 3

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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