Selective catalytic reduction of nitric oxide by hydrogen over Zn-ZSM-5 and Pd and Pd/Ru based catalysts

The catalytic reduction of NO with hydrogen (H-2-SCR) in excess oxygen over a non-noble metal catalyst, Zn-ZSM-5, was studied for the first time. The results showed that Zn-ZSM-5 had considerable activity for H-2-SCR, with a single NO conversion peak at 250 degrees C, and high N-2 product selectivity. Two noble metal based catalysts, Pd/Zn-ZSM-5 and Pd/Ru/W/(ZrO2-SiO2)SO4, were also synthesized and their H-2-SCR activities were evaluated and compared with Zn-ZSM-5 under identical laboratory experimental conditions. The effects of CO concentration, water vapor and SO2 added to the feed gas (NO, H-2, balance He) on H-2-SCR over these three catalysts were also studied and compared. hydrogen temperature programmed desorption (H-2-TPD) experiments were performed on Zn-ZSM-5: the results showed strong chemisorption of hydrogen, while both the amount and the binding strength of the chemisorbed hydrogen increased with the hydrogen dosing temperature. The role of Zn cations in the chemisorption is also discussed. (C) 2014 Elsevier B.V. All rights reserved.