Aerobic Oxidation Reactions Using Metal-based Heterogeneous Systems
This chapter deals with the use and development of heterogeneous non-precious metal oxide-based catalysts for aerobic oxidation reactions in gas–solid and liquid–solid phases. The main solid catalysts from transition metal ions (Mn, Cu, Fe, V, Ce, Nd, Mo, W) are described. Many examples are given about the reactions, catalytic performances, catalysts used and major industrial processes, either existing at present using petroleum-based raw materials or future processes using biomass-derived raw materials. It concerns selective oxidation and ammoxidation (NH
3 + O 2) reactions of alkanes to alkenes; alkanes to carboxylic acids, aldehydes and nitriles; olefins to carboxylic aldehydes and acids and aromatics to the corresponding acids or nitriles. Total oxidation reactions for depollution treatment and combustion are also briefly presented regarding atmospheric pollutants, such as industrial volatile organic compounds (VOCs). Some reaction mechanisms (radical-type or Mars and van Krevelen-type) along with concerns on the structure and size of active sites are discussed. Different reactor types, including packed bed, membrane and moving bed technology, are discussed depending on the intended reaction, as well as considerations on physical aspects of the solid catalysts, related to thermal and electrical conductivities, attrition resistance, deactivation and regeneration of the catalysts.