Selective lean NOx reduction over metal oxides

The present state of knowledge of NOx reduction under lean conditions over metal oxides is summarized in this review, with an emphasis on the reaction mechanism. Although a number of nitrogen-containing intermediates have been observed and implied, including organic nitro, nitrite, cyanide, isocyanate, and ammonia, there is yet definitive observation that confirms the relevance of these to the principal reaction pathway. Individual component in a mixed oxide catalyst can participate at different stages of the NOx reduction reaction. The nitrogen production efficiences for different oxide based catalysts are summarized, and their relationship to the nature of the catalyst is discussed.