6 - Transition metal oxides for combustion and depollution processes

Abstract

Transition metal oxides (M=Mn, Co, Fe, Ni,…) are potential catalysts for application in combustion and depollution processes. Owing to huge improvements in their preparation, perovskites, spinels, hexaaaluminates, and some other oxide structures can replace noble metals in a number of processes. In this chapter, the most recent advances in the use of oxides for total oxidation (CO, methane, COV, wet air oxidation) and for the treatment of nitrogen compounds (NOx, NH3, urea) will be reviewed. In every case, the most probable mechanism (Langmuir–Hinshelwood, Eley–Rideal, Mars–van Krevelen…) and the nature of active sites (Mn+/Mn+1 ion pairs, acid–base sites…) as well as the role of reactive oxygen species will be examined in the light of recent results and up-to-date concepts. Finally the outstanding progresses in the oxide synthesis allow to apply these concepts to the development of extremely active and more stable catalysts.