PROMOTIVE EFFECT OF ADDITIVES TO IN H-ZSM-5 CATALYST FOR SELECTIVE REDUCTION OF NITRIC-OXIDE WITH METHANE IN THE PRESENCE OF WATER-VAPOR/

It has been found that Ga and In/H-ZSM-5 are active catalysts for sele ctive NO reduction with methane, while the activities are retarded by water vapor, which particularly retards the oxidation of NO to NO2 on zeolitic Lewis acid sites, a necessary step for the reduction of NO wi th methane. In order to attain a H2O-tolerant catalyst based on In/H-Z SM-5, the substitute for Lewis acid sites was searched. After testing several metal species, it was found that In/H-ZSM-5 loading Pt, Rh and Ir exhibited high catalytic activity for NO reduction even in the pre sence of H2O.