Molecular structural and morphological characterization of polymer-supported Mo(VI) alkene epoxidation catalysts

Heterogeneous alkene epoxidation catalysts prepared by immobilization of sp ecies derived from MoO2(acac)(2) on two polymers, a polystyrene N-hydroxypr opyl aminomethylpyridine resin and a polybenzimidazole resin, are known to behave differently. The two catalyst species have now been characterized ex tensively in terms of both the molecular structure of the Mo(VI) centers an d the resin morphologies, and significant differences have been demonstrate d in both aspects. Molecular structural characterization has involved eleme ntal analysis and FTIR, electronic, and X-ray photoelectron spectroscopies, together with EXAFS analysis and associated modeling. Morphological studie s have employed high-resolution transmission electron microscopy with Mo ma pping, N-2 sorption, and Hg intrusion porosimetry and solvent imbibition me asurements. The differences observed account for the observed variation in catalytic behavior, and these structural and morphological differences are discussed in detail. (C) 1999 Academic Press.