Study on catalytic decomposition of ozone in air by Mn-modified zeolite molecular sieve.

The presence of ozone as a prominent indoor gaseous pollutant in human production and daily life necessitates the development of a high-efficiency ozone decomposition converter for source purification, with the catalyst being its pivotal component. This study investigates the catalytic performance of modified zeolite towards ozone. By altering the topological structure, cation form, modification, and drying methods, the adsorption and catalytic capabilities of zeolite were regulated. The Mn-USY-DT/WB zeolite catalyst can effectively and stably catalyze ozone for more than 30h at -5℃ and 720000h-1, and its regeneration performance is better than that of commercial MnO2 catalyst. XPS characterization results showed that the average oxidation state of elemental Mn decreased from 2.95 to 2.81 after regeneration. XRD results show that there is no significant difference in the diffraction peak Angle between the modified zeolite and the original USY, indicating that the cationic modification does not affect the crystal structure of zeolite molecular sieve. BET results show that the specific surface area of the modified sample is slightly lower than that of the original sample. The specific surface area of Mn-USY-YX sample was significantly reduced (146m2/g), indicating that Mn ion was related to the formation of a large number of hydrates by water molecules during the liquid phase sampling process, which was difficult to be removed by calcination. USY series samples have a large primary pore size (~0.74nm), Mn-Beta-DT zeolite modified samples have a small primary pore size of about 0.58nm, and Mn-ZSM-5-DT has the smallest primary pore size of 0.55nm. EDS images of the sample showed that the content of Mn in Mn-USY-YX was low and the distribution of Mn was discrete; the distribution of Mn in Mn-USY-DT/WB sample was uniform, mostly in linear arrangement along the crystal structure, and the Mn element was obviously aggregated in Mn-USY-DT/CG sample. By adjusting the modification method and drying method, the state of metal cationic polymer in zeolite skeleton can be preserved, and the metal clusters can be prevented from coming out of zeolite skeleton and aggregating, and the catalyst with higher activity can be obtained. Finally, the optimized modified zeolite powder was coated on glass fiber support to obtain a low gas resistance monolithic honeycomb catalyst which can maintain an efficiency of ≥99.9% for more than 1000h under practical application conditions.