Selective Oxidation: From a Still Immature Technology to the Roots of Catalysis Science
The design of heterogeneous selective oxidation catalysts based upon complex metal oxides is governed at present by a set of empirical rules known as "pillars of oxidation catalysis" They serve as practical guidelines for catalyst development and guide the reasoning about the catalyst role in the process. These rules are, however, not based upon atomistic concepts and thus preclude their immediate application in for example computer aided search strategies. The present work extends the ideas of the pillar rules and develops the concept of considering a selective oxidation catalyst as enabler for the execution of a reaction network. The enabling function is controlled by mutual interactions between catalyst and reactants. The electronic structure of the catalyst is defined as a bulk semiconductor with a surface state arising form a terminating over layer being different from the structure of the bulk. These components that can be identified by in situ analytical methods form a chemical system with feedback loops, which is responsible for generating selectivity during execution of the reaction network. This concept is based upon physical observables and could allow for a design strategy based upon a kinetic description that combines the processes between reactants with the processes between catalyst and reactants. Such kinetics is not available at present. Few of the constants required are known but many of them are accessible to experimental determination with in situ techniques.
Topics in Catalysis