Catalytic Ozonation of Polluter Benzene from −20 to >50 °C with High Conversion Efficiency and Selectivity on Mullite YMn₂O₅

Abstract

Catalytic decomposition of aromatic polluters at room temperature represents a green route for air purification but is currently challenged by the difficulty of generating reactive oxygen species (ROS) on catalysts. Herein, we develop a mullite catalyst YMn2O5 (YMO) with dual active sites of Mn3+ and Mn4+ and use ozone to produce a highly reactive O* upon YMO. Such a strong oxidant species on YMO shows complete removal of benzene from −20 to >50 °C with a high CO x selectivity (>90%) through the generated reactive species O* on the catalyst surface (60 000 mL g–1 h–1). Although the accumulation of water and intermediates gradually lowers the reaction rate after 8 h at 25 °C, a simple treatment by ozone purging or drying in the ambient environment regenerates the catalyst. Importantly, when the temperature increases to 50 °C, the catalytic performance remains 100% conversion without any degradation for 30 h. Experiments and theoretical calculations show that such a superior performance stems from the unique coordination environment, which ensures high generation of ROS and adsorption of aromatics. Mullite’s catalytic ozonation degradation of total volatile organic compounds (TVOC) is applied in a home-developed air cleaner, resulting in high efficiency of benzene removal. This work provides insights into the design of catalysts to decompose highly stable organic polluters.

Nanoporous CeO2-Decorated Cu-SmMn2O5 Composite Mullite Oxide Catalyst for Toluene Oxidation

“…Raman spectroscopy was used to study the vibrational modes of the species on the catalyst surface to evaluate the strength of bonds. In Figure a, based on the previous studies, the peaks around 191–209 cm –1 are assigned to the symmetric stretching vibration mode of the Mn–Mn dimer, and the peaks at a higher Raman shift (>600 cm –1 ) are ascribed to the asymmetric stretching vibration mode of the Mn–O–Mn structure, in which the peaks at 613 and 677 cm –1 correspond to the vibration of the Mn 4+ –O bond and Mn 3+ –O bond, respectively. ,,, It is clear that the three peaks are all observed in the SMO sample, confirming the formation of the mullite structure. The Raman peak intensity is correlated with the crystallite size, and the sharp Raman peak usually means that the crystallite size increases. , Compared with the SMO sample, the weakened and broadened Raman peaks are observed in the SCMO-Cu-IE sample indicating a decrease in the crystallinity, which is consistent with the above XRD results.…”

“…In Figure 6a, based on the previous studies, the peaks around 191−209 cm −1 are assigned to the symmetric stretching vibration mode of the Mn−Mn dimer, and the peaks at a higher Raman shift (>600 cm −1 ) are ascribed to the asymmetric stretching vibration mode of the Mn−O−Mn structure, in which the peaks at 613 and 677 cm −1 correspond to the vibration of the Mn 4+ −O bond and Mn 3+ −O bond, respectively. 17,18,41,42 It is clear that the three peaks are all observed in the SMO sample, confirming the formation of the mullite structure. The Raman peak intensity is correlated with the crystallite size, and the sharp Raman peak usually means that the crystallite size increases.…”

Transforming Plain LaMnO3 Perovskite into a Powerful Ozonation Catalyst: Elucidating the Mechanisms of Simultaneous A and B Sites Modulation for Enhanced Toluene Degradation

“…Adsorbed peroxide (*O 2 ) and atomic oxygen (*O) must be responsible for the peaks at 891 and 980 cm –1 , respectively . This result proves that Mn sites of the LCMO/MnO 2 -4.5 in the O 3 atmosphere will adsorb O 3 (directly at Mn sites or indirectly at surface – OH) and produce active *O 2 and *O to accomplish the oxidation of toluene . Catalytic ozonation typically results in a significant generation of surface-adsorbed oxygen species, which subsequently convert into various ROS, actively engaged in catalytic reactions .…”

“…58 This result proves that Mn sites of the LCMO/ MnO 2 -4.5 in the O 3 atmosphere will adsorb O 3 (directly at Mn sites or indirectly at surface − OH) and produce active *O 2 and *O to accomplish the oxidation of toluene. 59 Catalytic ozonation typically results in a significant generation of surfaceadsorbed oxygen species, which subsequently convert into various ROS, actively engaged in catalytic reactions. 60 These findings unequivocally demonstrate that the formation of • OH and O 2…”

Mn‐Based Mullites for Environmental and Energy Applications

“…[21,40] Using the intermediate radicals during ozone and H 2 O 2 decomposition, mullites show superior behaviors in the ozonization and hydrogen peroxide oxidation of VOCs at room temperature. [39,47] The unprecedented catalytic activity of Mn-based mullite oxide is due to its unique geometric and electronic structures. The unit occupation of the d z 2 orbital of pyramid Mn 3+ imparts special adsorption activity toward oxygen-containing species, thereby achieving excellent ORR/SRR activity.…”