Selective reduction of nitric oxide with methane on In/H-ZSM-5-based catalysts

There have been many studies on the catalysis of selective catalytic reduction of nitric oxide with hydrocarbons. It was shown in our previous works that Ir/In/H-ZSM-5 has high catalytic activity and selectivity for this reaction by use of methane as a reductant. The reaction of CH4-SCR proceeds consecutively as NO oxidation to NO2 and NO2 reduction with CH4. These two reactions take place bifunctionally on different kinds of catalytic sites: NO oxidation on Ir and NO2 reduction on InO+ sites. The studies of NOx chemisorption and kinetics of NOx reduction with CH4 lead us to conclude that the bifunctional catalysis is remarkably facilitated by the coexistence of these sites in the identical pores of zeolite, which may be called "intrapore catalysis". In this review, the design of highly active and selective catalysts for this reaction system will be discussed on the basis of bifunctionality. © Baltzer Science Publishers BV.