Topological Aspect of the Distribution of Co Species and N<sub>2</sub>O Decomposition Performance for Co/Zeolite Catalysts
Bin Kang, Runduo Zhang, Mengfei Guo, Xiaonan Guo, Zhaoying Di, Ying Wei, Jingbo Jia
Abstract
In this study, series of Co/zeolites with diverse microporous structures were prepared and applied for N 2 O catalytic decomposition. The corresponding activities followed the order Co/Beta > Co/Mordenite > Co/ZSM-5 > Co/MCM-49 > Co/ZSM-23 > Co/ZSM-35 > Co/SSZ-13, while the yield of NO 2 byproduct followed the order Co/ZSM-23 > Co/ZSM-35 > Co/MCM-49 > Co/Mordenite > Co/ZSM-5 > Co/Beta > Co/SSZ-13. Under conditions of 30 vol % N 2 O and GHSV = 30 000 h –1, the best performing sample (Co/beta) achieved a remarkable N 2 O conversion of 99.6% at 450 °C. In addition, the formation of NO 2 byproduct was significantly inhibited with the corresponding concentration varying from 1063 ppm for Co/ZSM-23 to 82 ppm for Co/Beta. Physicochemical characterization of these as-prepared catalysts was performed including XRD, BET, H 2 -TPR, NH 3 -TPD, XPS, UV-vis-DRS, and it was found that zeolites with higher dimensionally porous apertures (3D) and larger pore sizes (12-membered ring, 12-MR) were conducive to introducing Co ions onto the zeolite framework through the pore channels and further locating them on ion-exchange sites to form active centers (Co 2+ ). Furthermore, molecular dynamics simulation demonstrated that the higher pore dimensions and larger pore sizes are more beneficial for the N 2 O diffusion inside the pores and channels of zeolites and promote N 2 O decomposition.