The selective epoxidation of non-allylic olefins over supported silver catalysts

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Abstract

The epoxidation of non-allylic, or kinetically-hindered, olefins can be carried out using supported silver catalysts. While epoxidation does occur for unpromoted catalysts, the strength of olefin epoxide adsorption leads to low activity and selectivity, as well as irreversible catalyst fouling. The addition of certain alkali metal salts, such as CsCl, lowers the desorption energy of the olefin epoxide, permitting dramatic increases in activity, selectivity, and catalyst lifetime. In the case of butadiene, the addition of an optimum level of CsCl increases activity and selectivity from approximately 1% butadiene conversion and 50% selectivity for epoxybutene to 15% conversion and 95% selectivity, respectively.

Epoxidation of butadiene occurs by addition of dissociatively-adsorbed oxygen to one of the localized C=C bonds to form epoxybutene. The addition of oxygen across the terminal carbon atoms does not occur to any measurable extent. The direct participation of molecular oxygen can be ruled out based both on selectivity arguments as well as the kinetic model for the reaction. The kinetics imply a dual site mechanism. One site, which is unpromoted, serves as the site for butadiene adsorption, while the second site, which is promoted, functions as the site for dissociative oxygen adsorption and epoxybutene formation.

Epoxybutene and derivatives represent the beginning of several new families of chemicals that were either not available, or were too expensive, to be considered for large-scale, or even fine chemical, production. More than one hundred chemicals have been prepared so far; several of these are in commercial production at the semiworks scale.

References (21)

  • R.K. Grasselli et al.

    Adv. Catal.

    (1981)
  • S. Hawker et al.

    Surf. Sci.

    (1989)
  • N.W. Boaz et al.

    Tetrahedron: Asymmetry

    (1994)
  • Chem. & Eng. News

    (1996)
  • J.A. Dean
  • J. R. Monnier and P. J. Muehlbauer, U.S. Patent No. 4,897,498...
  • J. R. Monnier and P. J. Muehlbauer, U.S. Patent No. 4,950,773...
  • J. R. Monnier and P. J. Muehlbauer, U.S. Patent No. 5,081,096...
  • J.T. Roberts et al.

    J. Am. Chem. Soc.

    (1991)
  • B. Schiott et al.

    J. Phys. Chem.

    (1993)
There are more references available in the full text version of this article.

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