Synergistic removal of NO and soot by Fe-W-Zr-ZSM-5 catalysts in a wide temperature window

Abstract

Obtaining the synergistic catalytic removal of NO and soot is a highlight topic as both NO and soot are the main pollutants from diesel engine. However, synergistic catalytic removal is still very difficult because the temperature window varies with the traditional SCR catalyst of NO at narrow temperature of 300–450 ℃ and the oxidation temperature of soot at high temperature of 500–700 ℃. Therefore, based on W-Zr-ZSM-5 catalyst, a series of M-W-Zr-ZSM-5 (M = Cu, Fe or Nb) catalysts were prepared by sol–gel method to investigate the synergistic catalytic removal of NO and soot, which emitted from diesel engine at the same time. The results showed that Fe-W-Zr-ZSM-5 catalyst exhibited the best NH3-SCR reaction activity and oxidizing performance of soot among the catalysts, with more than 90 % NO conversion in the temperature range of 320 ℃ to 580 ℃ and completely oxidization of soot in the temperature range of 432 ℃ to 543 ℃. The results of XRD, BET, XPS and Raman spectrum indicated that there was strong interaction between W and Fe, promoting the formation of W5+ and W = O species, thereby increasing the content of chemisorbed oxygen, the amount of surface acid sites and redox capacity of the catalysts. Meanwhile, the redox capacity of Fe-W-Zr-ZSM-5 was responsible for the improvement of NH3-SCR activity and the oxidation of soot at low temperature. Fe-W-Zr-ZSM-5 catalyst demonstrated to be a promising material to synergistic remove NO and soot.