Zn-promoted Rh/SiO2 catalyst for the selective reduction of NO with H2 in the presence of O2 and SO2

The effect of metal additives on the catalytic performance of Rh/SiO2 for the selective reduction of NO with H2 in the presence of O2 and SO2 was investigated. The addition of Zn was effective to enhance the catalytic activity of Rh/SiO2 for NO reduction at low temperatures and high O2 concentrations. The structural characterizations of Zn/Rh/SiO2 samples and in situ FT-IR measurements revealed that Zn additive plays two important roles in enhancing the catalytic activity of Rh/SiO2: (i) prevention of catalyst deactivation as an oxidation-retardant for the active Rh metal species supported on SiO2 and (ii) promotion of a reaction step, which generates NHx species as a key reaction intermediate for NO reduction by H2 in the presence of O2 and SO2.