Haiwen Xu,Danyang Li,Lei Jiang,Chunqiang Lu,Jiangyong Yuan,Zhiqiang Li,Yuelun Li,Huicong Zuo,Kongzhai Li
It is challenging to load precious metals nanoparticles on LaFeO 3 perovskite with small specific surface, and to improve the thermal stability of precious metals is also very difficult. Therefore, it is of great significance to disperse precious uniformly on perovskite with low specific surface area and to make the catalyst with high catalytic activity and thermal stability. In this work, we develop series of perovskite-based methane combustion catalysts with good catalytic activity and stability. Compare with traditional LaFeO 3 catalysts, the catalytic activity of three-dimensional ordered macroporous (3DOM) LaFeO 3 significantly improves by loading Pt. In addition, its thermal stability is significantly improved by adding CeO 2 , especially at high roasting temperature (800 °C). The 1 wt%Pt/10 %CeO 2 /3DOM LaFeO 3 catalysts shows the highest catalytic activity in which the T 10 , T 50 and T 90 are 362 °C, 433 °C and 502 °C, and its recaction temperature of T 50 is decreased by 50 °C compare with Pt/3DOM LaFeO 3 (8 0 0). The different physical and chemical characterizations suggest that the coupling of Ce 3+ and Fe 2+ induces the formation of a large number of oxygen vacancies, which promotes the oxygen mobility and th oxygen storage capacity during the methane oxidation process. More importantly, the CeO 2 addition contributes to the Pt-CeO 2 interaction with Ce-O-Pt bond formation, which greatly improves the thermal stability of the catalyst, and this Pt-CeO 2 interaction strength becomes more obvious with the increase of calcination temperature. Furthermore, the in-situ DRIFT experiments indicate that M−K mechanism is probably involved in the reaction process.
Shuaiqi Ning,Shuai Mao,Chun Liu,Mingzhu Xia,Fengyun Wang
In this paper, some perovskite catalysts LaFeO3 (LFO) were prepared by using the efficient chelating properties of sodium diethylene triamine pentamethylene phosphonate (DTPMP-2Na) toward metal ions, and the best catalyst LFO-0.1 was selected by using diclofenac sodium as the target pollutant. Then, the influence of different factors (PMS dosage, catalyst dosage, substrate concentration and anion) on the degradation of DCF in a LFO-0.1/PMS system was studied. The catalyst was characterized, and the reaction mechanism of diclofenac (DCF) in the LFO-0.1/PMS system was analyzed. It was concluded that hydroxyl radicals, sulfate radicals and singlet oxygen were produced in the LFO-0.1/PMS system. In the reaction system, singlet oxygen is considered to be the main factor for DCF degradation in this system, and the generation of sulfate radicals is mainly attributed to oxygen vacancies and the electron transfer between Fe3+ and Fe2+. Through the centrifugal recovery of the catalyst to explore its stability, the conclusion is that LFO-0.1 is a stable catalyst. Finally, 15 kinds of oxidation intermediates and products were identified, and the possible degradation pathways of DCF were analyzed, including decarboxylation, dechlorination, C–N cleavage, hydroxylation, ring-closure and ring-opening.
Li Yumei,Deng Bingqian,Wang Jiexin,Li Jialong,An Wenbin,Fan Jian,Sun Peng
A molybdenum (Mo)-modified LaFeO 3 (LFMO) perovskite catalyst was synthesized to activate peroxymonosulfate (PMS) for the degradation of indole in solution. The catalyst was characterized by XRD, SEM, and XPS. Results indicate that LFMO possesses a higher specific surface area and more catalytic active sites compared to unmodified LaFeO 3 . XPS analysis reveals that the activation of PMS is mediated by Fe 2+ /Fe 3+ and Mo 4+ /Mo 6+ reduction–oxidation cycles. Oxygen vacancies generated by molybdenum substitution serve as reaction sites, which accelerate the dissociation of PMS and the production of reactive oxygen species. Chemical quenching experiments and EPR spectroscopic analyses were employed to elucidate the mechanism, highlighting the significant role of non-radical species in the removal of indole. Under optimal reaction conditions, the degradation efficiency of indole reached 90.53% within 30 min, demonstrating strong anti-interference against inorganic anions and natural organic matter. LFMO particles exhibit sustained catalytic activity and stability over five consecutive cycles. This LFMO/PMS system provides valuable insights for the development of non-radical degradation pathways based on PMS.
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