Emerging applications of environmentally friendly zeolites in the selective catalytic reduction of nitrogen oxides

Abstract

The catalytic removal of nitrogen oxides (NOx) from diesel exhaust under oxygen-rich conditions remains a major challenge in the field of environmental catalysis, and the selective catalytic reduction of NOx with NH3 (NH3-SCR), especially over zeolite catalysts, is a well-proven technique for the catalytic deNOx process for diesel vehicles. The comprehensive understanding of the structure-activity relationship of zeolite catalysts in the NH3-SCR reaction and the elucidation of the detailed reaction mechanism are very important for the practical use of these catalytic materials. In this chapter, using the environmentally friendly Fe- and Cu-based zeolite catalysts (i.e. Fe-ZSM-5, Cu-ZSM-5, Cu-SSZ-13 and Cu-SAPO-34, etc.) as examples, the influence of preparation methods on NH3-SCR performance, the role of metal active sites/surface acid sites, the impact of NO2 and co-existing pollutants, the hydrothermal stability and also the possible SCR reaction pathways over these materials are discussed in detail, which can provide theoretical and empirical guidance for the redesign and activity improvement of these catalysts in their practical applications.