Niobium-silica catalysts for the selective epoxidation of cyclic alkenes: the generation of the active site by grafting niobocene dichloride

Phys Chem Chem Phys. 2013 Aug 28;15(32):13354-62. doi: 10.1039/c3cp51570b.

Abstract

Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(iv) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(v) site, tripodally grafted onto the silica surface in close proximity to other Nb(v) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium-silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Catalysis
  • Catalytic Domain
  • Cycloparaffins / chemistry*
  • Cyclopentanes / chemistry*
  • Epoxy Compounds / chemical synthesis*
  • Epoxy Compounds / chemistry
  • Niobium / chemistry*
  • Organometallic Compounds / chemistry*
  • Silicon Dioxide / chemistry*

Substances

  • Cycloparaffins
  • Cyclopentanes
  • Epoxy Compounds
  • Organometallic Compounds
  • Niobium
  • niobocene dichloride
  • Silicon Dioxide