Catalytic and physico-chemical properties of new schiff base complexes in zeolites

Abstract

Adsorption of tetradentate Schiff base ligands on Mn^IINaY zeolites yields catalysts for selective oxidation of hydrocarbons with PhIO or tert-butylhydroperoxide (tBHP). The interaction between Mn and the ligands is proved by IR, diffuse reflectance and EPR spectroscopy. Olefin epoxidation with these catalysts suffers from formation of undesirable products when tBHP is used, but reasonable epoxide selectivities are obtained with PhIO. Very active catalysts for alkane oxidation with tBHP are produced by adsorption of the pyridine derived pyren and pyrpn ligands on Mn^IINaY (pyren = bis(2-pyridinecarboxaldehyde)ethylenediimine; pyrpn = bis(2-pyridinecarboxaldehyde)propylenediimine). With these catalysts, very high selectivities are obtained for formation of monoketones from alkanes. A relation is proposed between the appearance of low-field features in the Mn(II) EPR spectra and a high activity in hydrocarbon oxidation.