Effect of acid/alkali treatment on the structure and catalytic performance of 3DOM CeCo0.7Mn0.3O3 catalyst.

In this work, Ce was used as the A-site element and three-dimensional ordered macroporous (3DOM) materials as the template to obtain 3DOM CeCo0.7Mn0.3O3 catalyst via excessive impregnation method. The catalyst was subjected to acid/alkali treatment with dilute nitric acid and sodium hydroxide solutions. The results revealed that the catalysts subjected to acid/alkali treatment exhibited better structural and catalytic activity characteristics than the bulk catalyst. Specifically, the specific surface area of the catalyst treated with acid increased from 34.86 to 60.67 m2·g-1, and the relative contents of Oads and Mn4+ species increased. Moreover, the T90% further decreased to 174 °C. As for the catalyst treated with alkali, it exhibited a rougher surface and a wider pore size distribution, producing more lattice defects which were favorable for reaction progress. The T90% was 183 °C, indicating that acid/alkali treatment both had a positive effect on the catalytic oxidation of toluene.

Effect of B-Site Element on the Structure and Catalytic Performance for Toluene of the 3DOM CeBO3 Catalyst.

A series of 3DOM cerium-based perovskite catalysts with different B-site elements were prepared by the colloidal crystal template method and excess impregnation method with Cr, Ni, and Mn as the B-site elements. The physical and chemical properties of the catalysts were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), and oxygen temperature-programmed desorption (O2-TPD) characterization techniques. The results showed that the catalyst with Mn as the B-site element had a high-quality macropore structure (pore size 200-250 nm), large specific surface area (45.26 m2/g), and abundant surface adsorbed oxygen content (Oads/Olatt = 0.46). The addition of manganese enhanced the low-temperature reducibility, and the main reduction peak was below 400 °C. The O2-TPD results showed that 3DOM CeMnO3 expressed the highest adsorption oxygen content. The 3DOM CeMnO3 possessed the best catalytic performance with T50% = 102 °C and T90% = 203 °C during the catalytic oxidation of toluene. Intermediate product study hinted that toluene was first converted into benzoic acid and benzaldehyde and then further degraded into small molecules. The catalyst with the best activity also exhibited good stability, and toluene degradation rate remained above 85% at 200°C for more than 20 h of continuous experiments.