(495f) Magnesia and Zirconia Mixed Oxide Catalysts for Transesterification and Carbon-Carbon Coupling Reactions

Although magnesia is a commonly recognized solid base, addition of zirconia to magnesia can accelerate the rate of some base-catalyzed reactions.  This presentation explores the influence of zirconia addition to magnesia on the rate of transesterification of tributyrin with methanol and the rate of acetone condensation.  Small amounts of zirconia substantially promote the reaction rates over those on pure magnesia, presumably through the cooperative action of the Lewis acid and base sites on the mixed oxide.  However, when highly-active Mg:Zr mixed oxide catalysts are evaluated in the Guerbet coupling of ethanol to butanol, competing undesirable reactions occur on the Lewis acid sites of the zirconia.  X-ray diffraction, electron microscopy, carbon dioxide and ammonia adsorption microcalorimetry, and FT-IR spectroscopy of adsorbed methanol were used to characterize the structure and acid-base surface properties of the mixed oxides.  The reactivity studies combined with detailed materials characterization results provide insights into the potential design of new mixed metal oxide catalysts with acid-base bifunctionality for specific target reactions.