Recent Progress in the Application of Transition-Metal Containing MFI topologies for NH3-SCR-DeNOx and NH3 oxidation

Abstract

Transition metal-containing MFI-based catalysts are widely investigated in the selective catalytic reduction of NOx with ammonia (NH3-SCR-DeNOx), and the selective catalytic oxidation of ammonia (NH3-SCO) into nitrogen and water vapor. While MFI-based catalysts are less intensively studied than smaller pore zeolites (i. e., chabazite, CHA) they are still used commercially for these processes and are of great interest for future study in particular to better understand structure-activity relationships. Hierarchically porous MFI catalysts (containing both micropores and mesopores) often show enhanced catalytic properties compared to conventional (microporous) materials in both NH3-SCR-DeNOx and NH3-SCO. Thus, a critical overview of the current understanding of the salient physico-chemical properties that influence the performance of these catalysts is examined. Furthermore, strategies for the development of ZSM-5 based catalysts with enhanced catalytic lifetime, supported by the investigations of reaction mechanisms are reviewed and discussed.