Grafted Ta-calixarenes: Tunable, selective catalysts for direct olefin epoxidation with aqueous hydrogen peroxide

Natalia Morlanés, Justin M Notestein

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Supported Ta(V) oxide catalysts were prepared by grafting calixarene-Ta(V) and TaX5 complexes on SiO2 at coverages less than 0.25 Ta nm-2. Thermogravimetric and elemental analyses and UV-visible spectroscopy indicate that catalysts consist of isolated, 1:1 Ta:ligand surface sites. Catalysts obtained by this one-pot procedure were studied in cyclohexene and cyclooctene epoxidation with H2O2. In sharp contrast with bare oxides, calixarene-containing catalysts had initial cyclohexene direct epoxidation turnover rates of 3.9 ± 0.1 × 10-2 s -1 unaffected by surface density, demonstrating single-site character. Calixarene-containing catalysts were up to 3× more active than the corresponding TaCl5-based catalysts at high surface densities and were also up to 95% selective to direct (non-radical) cyclohexene epoxidation versus 5-based catalysts or only ∼20% selectivity for grafted calixarene-Ti(IV) catalysts. Capping silanols with octanol reduced epoxide hydrolysis from >50% to 2O2 and demonstrate that a surface ligand on an otherwise traditionally prepared supported oxide can selectively direct oxidation down mechanistically distinct pathways.

Original languageEnglish
Pages (from-to)191-201
Number of pages11
JournalJournal of Catalysis
Volume275
Issue number2
DOIs
Publication statusPublished - Oct 22 2010

Fingerprint

Calixarenes
epoxidation
Epoxidation
Alkenes
hydrogen peroxide
Hydrogen peroxide
Hydrogen Peroxide
alkenes
Olefins
catalysts
Catalysts
Oxides
oxides
Ligands
Octanols
ligands
epoxy compounds
Catalyst selectivity
Epoxy Compounds
hydrolysis

Keywords

  • Allylic hydroperoxide
  • Calixarene
  • Green chemistry
  • Heterogeneous catalyst
  • Hydrogen peroxide
  • Olefin epoxidation
  • Single-site catalyst
  • Supported catalyst
  • Supported oxide
  • Tantalum

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

Cite this

Grafted Ta-calixarenes : Tunable, selective catalysts for direct olefin epoxidation with aqueous hydrogen peroxide. / Morlanés, Natalia; Notestein, Justin M.

In: Journal of Catalysis, Vol. 275, No. 2, 22.10.2010, p. 191-201.

Research output: Contribution to journalArticle

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