Solid state aspects of oxidation catalysis

The main subject of this review is the consideration of catalytic oxidation reactions, which are greatly influenced by solid state effects in the cata lyst material. Emphasis is laid upon the correlation between the presence o f mobile ionic defects, together with the associated ionic conductivity, an d the catalytic performance. Both total and selective oxidation reactions a nd oxidative conversion reactions are considered. Well-known examples of su ch behaviour include oxidative methane conversion with lanthanide oxides, c arbon monoxide oxidation on fluorite type catalysts, selective olefin oxida tion using vanadia based catalysts, etc. Furthermore, because oxygen exchan ge between gas and solid is always part of the oxidation process, this is c onsidered too. The discussion of the application of the solid oxides under consideration t o practically important oxidation processes, together with the influence th ereon of their solid state properties, forms a major part of this review. C omputational modelling and simulation of catalyst structure and behaviour i s also considered. Special attention is given to the potentialities offered by using ionic and mixed conducting oxides either as the electrode material in a solid electr olyte fuel cell (SOFC) or as a separating, dense membrane in a ceramic memb rane reactor. The use of porous membranes in such reactors is also taken in to consideration. On the one hand these may be used to study the above rela tionship between catalytic behaviour and solid state properties, on the oth er hand to obtain a reactor configuration allowing better use of reactants and/or catalysts. Besides the controlled supply of (or removal) of oxygen t o (or from) the side where the catalyst and the reactants are located, a pr omising feature of both experimental approaches is that the oxygen flux may alter the relative presence of different oxygen species (O-2, O, O-2(-). O -2(2-), O-3(-), O-, etc.) on the catalyst surface. In this way species are provided having a strong influence on the selectivity for partial oxidation reactions and oxidative conversion reactions. (C) 2000 Elsevier Science B. V. All rights reserved.