Characterization and catalytic investigation of Fe-ZSM5 for urea-SCR

A Consistent Reaction Scheme for the Selective Catalytic Reduction of Nitrogen Oxides with Ammonia

“…15 Based on the fact that the SCR reaction becomes much faster in the presence of NO 2 , this step has also been proposed as the rate determining step for the standard SCR reaction. [56][57][58][59] The adsorbed NO 2 is the first step in the formation of reactive nitrate and nitrite species, 15,40 which could occur by disproportionation of two NO 2 molecules to 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 NO an isolated negative charge on the catalyst, or the second oxygen atom in 1 2 O 2 must be accommodated in the catalyst. These changes have to be restored as well in order to close the catalytic cycle.…”

Effect of Oxygen Concentration in NH₃-SCR Reaction over Fe- and Cu-loaded Beta Zeolites

“…The presence of NH3 suppressed the oxidation of NO to NO2, leading to reduction in the NH3-SCR activity, with the apparent reaction order of NH3 being zero or of negative order. The inhibition effect of NH3 strongly indicates the possibility of NH3 adsorption onto the active sites 5), 9) , the reduction of a loaded metal 10) , or NH3 oxidation 6) . On the other hand, for Cu-loaded zeolite catalysts, several ratedetermining steps were proposed, such as NO oxidation to NO2 1), 11) , oxidative adsorption of NO 12) , or oxidation of Cu to Cu 2 13) .…”

Hydrothermal Deactivation of Fe-ZSM-5 Prepared by Different Methods for the Selective Catalytic Reduction of NOx with NH3

“…For a given parent zeolite, the activity of Fe-ZSM-5 for NH 3 -SCR depended strongly on the preparation method. Among various methods for Fe-ZSM-5 preparation, liquid ion exchange (IE) [6][7][8], incipient wetness impregnation (IWI) [7][8][9][10], chemical vapor deposition (CVD) [11][12][13][14][15], and solid state ion exchange (SSIE) [16][17][18] are well known.The performance of Fe-ZSM-5 in the NH 3 -SCR reaction is related to the Fe species distributions on the catalyst. According to the results of UV-Vis diffuse reflectance spectroscopy (DRS), Mössbauer, and electron paramagnetic resonance (EPR) spectroscopy, the Fe species coexisting on Fe-ZSM-5 in some studies of the application of Fe-ZSM-5 in NH 3 -SCR are SHI Xiaoyan et al / Chinese Journal of Catalysis, 2012, 33: 454-464 One of the challenges for the practical application of Fe-ZSM-5 catalysts is their limited hydrothermal stability at high temperatures [4,5].…”

“…For a given parent zeolite, the activity of Fe-ZSM-5 for NH 3 -SCR depended strongly on the preparation method. Among various methods for Fe-ZSM-5 preparation, liquid ion exchange (IE) [6][7][8], incipient wetness impregnation (IWI) [7][8][9][10], chemical vapor deposition (CVD) [11][12][13][14][15], and solid state ion exchange (SSIE) [16][17][18] are well known.…”