Hydrothermal aging mechanism of K/CeO2 catalyst in soot catalytic combustion based on the Ostwald ripening mechanism. (1st January 2023)

• Record Type: Journal Article
• Authors: Li, Zonglin; Wang, Pan; Ao, Chengcheng; Meng, Zhongwei; Zhang, Lidong
• Is Part Of: Thermal science and engineering progress. Volume 37(2023)
• Publication Date: 2023-01-01
• Subjects: Soot catalytic combustion -- K/CeO2 catalyst -- Hydrothermal aging -- DFT; Heat engineering -- Periodicals; Heat engineering; Thermodynamics; Periodicals; 621.402
• DOI: 10.1016/j.tsep.2022.101593
• Languages: English
• ISSNs: 2451-9049

Abstract

Graphical abstract: Highlights: Catalytic activity of K/CeO2 decreased more than CeO2 after hydrothermal aging. Change in valence, lattice and catalytic activity of catalysts were investigated. Hydrothermal aging mechanism based on Ostwald ripening was explained with DFT. Abstract: The thermogravimetric analysis (TGA) experiment of CeO2 and K/CeO2 catalysts prepared with the incipient wetness impregnation method was carried out for the soot catalytic combustion at different K loadings before and after hydrothermal aging. The structure, morphology, and catalytic activity of CeO2 and K/CeO2 catalysts were thoroughly investigated with the means of N2 adsorption/desorption, XRD, XPS, and H2 -TPR. The density functional theory (DFT) operation was applied to explain the mechanism of the decrease in catalytic activity of CeO2 and K/CeO2 catalysts after hydrothermal aging. TGA showed that the Tmax of the hydrothermal aging K/CeO2 catalyst was 505 °C, which was higher than CeO2 at 473 °C. After hydrothermal aging, CeO2 catalysts were less agglomerated than K/CeO2, and the ratio of Ce 3+ /Ce 4+ decreases, but the mobile oxygen OII /OI ratio in the lattice were increased compared to CeO2 catalysts. DFT calculations showed that K doping significantly increases the surface energy and decreases the oxygen vacancy formation energy of (1 1 1), (2 0 0), (2 2 0), and (3 1 1) crystal planes, leading to enhanced catalytic combustion performance of the K/CeO2 catalyst soot based on the Mars-Van Krevelen mechanism. Furthermore, K doping decreased the adsorption energy of H2 O and the energy barrier of K atoms diffusing near the surface of K/CeO2 catalyst crystals from 5.92 eV to 2.46 eV, which resulted in the loss of the active center number because of migration and coalescence (sintering) caused by crystal plane instability based on the Ostwald ripening mechanism.