Yukihiro Sugiura

Promotive effect of additives to In/H-ZSM-5 catalyst for selective reduction of nitric oxide with methane in the presence of water vapor

Abstract It has been found that Ga and In/H-ZSM-5 are active catalysts for selective NO reduction with methane, while the activities are retarded by water vapor, which particularly retards the oxidation of NO to NO 2 on zeolitic Lewis acid sites, a necessary step for the reduction of NO with methane. In order to attain a H 2 O-tolerant catalyst based on In/H-ZSM-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 presence of H 2 O.

Reduction of nitric oxide with methane on Pd/Co/H-ZSM-5 catalysts: cooperative effects of Pd and Co

Reduction of low concentration of nitric oxide (NO) with methane as a reductant under wet conditions has been investigated using Pd/Co/H-ZSM-5 catalysts and the effects brought about by coexistence of Pd and Co are discussed. The role of Co is attributed to the acceleration of oxidation of NO to NO2, which is the necessary species for reduction of NO with CH4 on Pd sites. A Pd/H-ZSM-5 loading of 1 wt% Co shows a maximum activity for NO reduction as well as for NO oxidation. Excess loading of Co led to a decrease in activity for NO reduction. An XPS study shows that Pd and Co are well dispersed inside the zeolite when the concentrations of Pd and Co are less than 1 wt%. Loading of excess Co, however, causes aggregation of Pd on the surface of ZSM-5.