Characterization of cuprous ion in high silica zeolites and reaction mechanisms of catalytic NO decomposition and specific N2 adsorption

In this review, we have summarized the recent studies on the characterization of copper ions exchanged into MFI (CuMFI) and suggested the models of active centers for the NO decomposition and the specific N-2 adsorption. The first part deals with the reduction mechanism of copper ions exchanged in MFI during the evacuation process at high temperature. In the second part, it has been claimed that a part of the Cu+ species, formed in the evacuation process, take three-coordination structure at the M7 site and are active for the N-2 adsorption. The N-2 adsorption would result in the change in the Cu structure to the distorted tetrahedral coordination. The third part concerns the reaction mechanism of NO decomposition. We have proposed that the Cu+-Cu+ dimer species are indispensable for the effective NO decomposition and the oxygen-bridged intermediates are produced during the catalytic cycle.