Catalytic oxidation studies with platinum and palladium

Abstract

This study of the platinum- and palladium-catalyzed oxidation of selected organic compounds includes aliphatic alkanes, alkenes, alcohols, and ketones. The relationship between chemical structure of reactants and the kinetic parameters of the catalytic reaction (activation entropy and activation energy) is elucidated by these measurements. Fractional surface coverage of the catalyst with chemisorbed oxygen and hydrogen abstraction from the organic compound appear to control the rates of catalytic oxidation. In the alkane series the activation energy diminishes to a constant value at butane. But the observed variations in activation entropy point to electron promotion from the adsorbate to a localized band of the solid as an important aspect of bond formation. Palladium is a less efficient oxidation catalyst than platinum primarily because of the stable oxide (PdO) formed, which exhibits catalytic properties of a metal-oxide semiconductor rather than those of a metal. In the oxidation of 2-propanol over platinum, the formation of acetone at a catalyst temperature near 385 °K was observed.