Comparison of alkaline pre‐treatment of MFI zeolites for N₂O decomposition: different zeolite sources

Abstract

Three MFI parent zeolites with different morphological properties by different synthesis method were adopted. Alkaline treatment using sodium hydroxide was introduced to modify the structure of MFI zeolites. After iron exchange, the catalytic performance of both parent and modified MFI zeolites were evaluated in the N 2 O decomposition. The physicochemical properties were systematically characterized with various technologies, such as N 2 adsorption-desorption, ICP, XRD, UV-Vis, 27 Al MAS-NMR, TEM. The experiment results prove that the Fe-modified MFI catalysts with alkaline pre-treatment show much better catalytic activity than Fe-exchanged parent MFI catalysts. The curves of catalytic activities could move to low temperature range by 50-100°C. Furthermore, in the presence of NO, the performance gap between Fe-Seed-M, Fe-Solid-M, and Fe-Com-M three samples is obviously reduced. Amongst, for the Fe-Solid-M sample synthesized by the solvent-free method, 90% N 2 O conversion could be attained at 500°C, which shows potential to be applied the real condition. It is believed the hierarchical properties and the removal of amorphous substance is beneficial to the diffusion of ion exchange process. Therefore, the increase of active iron sites contributes to the improvement of catalytic performance. C

Application of Mesoporous/Hierarchical Zeolites as Catalysts for the Conversion of Nitrogen Pollutants: A Review

“…O2* + * ↔ 2O* (11) N2O + O* → N2 + O2 + * (12) Several studies have focused on mesoporous Fe-ZSM-5 zeolites prepared by desilication and their activity in the decomposition of N2O. Different desilication conditions, such as 0.2 M NaOH solution, 80 °C, treatment for 30 and 120 min [95]; 0.2 M NaOH, 90 °C, 90 min [96]; and a mixture of NaOH and TPAOH (different TPA+/OHratios), 90 °C, 90 min [97] were applied to determine the influence of this modification method on their catalytic performance. Iron was introduced into desilicated zeolite samples by ion exchange with the use of Fe(NO3)3•9H2O solution.…”