Radicals in Catalysis- Heterogeneous

Several reactions in heterogeneous catalysis take place via radical intermediates. The present article illustrates the typical aspects of the radical chemistry in heterogeneous catalysis that very often differ from those in the radical chemistry in fluid homogeneous phases because of the role of the surface in the generation, stabilization, and transformation of radical species. The various routes for the formation of radicals on a surface will be taken into consideration including electron transfer, atom transfer, and molecular dissociation. A particular emphasis is given to the electron magnetic resonance techniques, which have the paramount role in the detection and also in the description of the radical species because of their high sensitivity that allows the detection of low abundance species. In the final part of the article some selected examples of heterogeneous catalytic processes involving radical steps will be discussed with particular emphasis on catalytic oxidation on metal oxides.