Zihao Hu,Xiaoying Zhou,Tiantian Zhang,Zuliang Wu,Jing Li,Wei Wang,Erhao Gao,Jiali Zhu,Shuiliang Yao
Aiming at the problem of the poor performance of an Mn-MOF-74-derived Mn3O4 catalyst in low-temperature carbon monoxide (CO) oxidation, copper (Cu) and cerium (Ce) elements were used to modify the Mn3O4 catalyst to improve its performance in low-temperature CO oxidation. According to the results of catalytic performance testing, the CO oxidation activity of the Cu0.3Mn2.7O4 catalyst was significantly improved compared with that of the pristine Mn3O4 catalyst, when a CO conversion rate of 90% was achieved at 118 °C. According to X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analyses, the (Mn2+ + Mn3+)/(Mn2+ + Mn3+ + Mn4+) ratio and the Oads/Ototal ratio increased after Cu doping, indicating promoted oxygen vacancy generation. In addition, the increased specific surface area was beneficial for the adsorption of reactant molecules and the exposure of active sites. According to H2-temperature-programmed reduction characterization, Cu doping significantly enhanced the performance of the Cu0.3Mn2.7O4 catalyst during low-temperature redox. Finally, these factors synergistically promoted the degradation of CO over the Cu0.3Mn2.7O4 catalyst. In addition, operando diffuse reflectance Fourier transform infrared spectroscopy results suggested the presence of more terminal-type oxygen, which is essential for the catalytic oxidation of CO on the surface of the Cu0.3Mn2.7O4 catalyst. Moreover, the Cu0.3Mn2.7O4 catalyst also showed excellent resistance to carbonate, and remarkable stability.
Jie Fan,Lutao Mao,Mingli Fu,Peng Liu,Zuliang Wu,Daiqi Ye
The high efficiency and stability of catalysts are crucial for their practical application in toluene oxidation . Herein, a novel octahedral Pt/Mn 3 O 4 -110 catalyst with excellent structural stability was synthesized and 100 % toluene conversion can be achieved at low-temperature 160 °C. XRD and Raman results indicated that the structure of Pt/Mn 3 O 4 -110 can be well maintained after 120 h on-stream reaction, the resistance to H 2 O (3 or 5 vol%) and high concentration toluene (3000 ppm)/CO 2 (5 vol%) tests. In situ DRIFTS comparative studies between Pt/Mn 3 O 4 -110 and Pt/Mn 3 O 4 -100 (30 % toluene conversion at 160 °C) samples demonstrated that the rate-control steps of toluene oxidation on Pt/Mn 3 O 4 -110 and Pt/Mn 3 O 4 -100 were both the further oxidation of benzoate species in the presence of gas-phase oxygen, while the transformation of benzaldehyde to benzoate species was the rate-control step on Pt/Mn 3 O 4 -100 in the absence of gas-phase oxygen. The weaker Mn-O bonds, richer oxygen vacancies and higher mobility of oxygen species on Pt/Mn 3 O 4 -110 sample than that of Pt/Mn 3 O 4 -100 are beneficial for the easier release of lattice oxygen from the surface of catalyst and then participated in toluene oxidation via Mars-van Krevelen mechanism, contributing to easier oxidation of benzaldehyde to benzoate species and formation of formic acid and bicarbonate species.
Adjusting the interaction between dual active components for enhancing volatile organic compounds (VOCs) degradation is an effective but still challenging means of air pollution control. Herein, a limited pyrolysis oxidation strategy was adopted to prepare Pd-Mn 3 O 4 spinel catalysts with uniform morphology and active component dispersion. Among these, 1.08Pd-Mn 3 O 4 presented the highest catalytic efficiency with a T 90 value of 240 °C, which was 94 °C lower than that of Mn 3 O 4 . Characterization and density functional theory (DFT) calculation results revealed that the strong metal-support interaction (SMSI) effect between Pd and Mn 3 O 4 promoted the redistribution of surface charges, thus strengthening the oxidation-reduction ability of the active sites. Moreover, the SMSI effect led to a better migration of surface oxygen species, and boosted the generation of active surface oxygen species. Simultaneously, the Pd catalyst further reduced the energy barrier in the initial stage of the dehydrogenation of propane. Overall, this study provided a novel design strategy for dual active components catalysts with SMSI effect and extended the application of these catalysts in the important field of VOCs elimination.
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