Catalytic combustion of soot on Ce-Fe-Zr-O ternary mixed oxide catalysts
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Graphical Abstract
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Abstract
Pure CeO2, Fe2O3 and a series of Ce0.5Fe0.5-xZrxO2 mixed oxide catalysts for soot catalytic combustion were prepared via hydrothermal method and characterized by XRD, Raman spectroscopy, H2-TPR and BET measurements. The catalytic activities in the diesel soot oxidation were tested by using temperature-programmed oxidation (TPO) reaction apparatus. The results show that all of the Zr4+ incorporated into the CeO2 lattice to form a solid solution. On the other hand, Fe3+ is extremely difficult to dissolve into the CeO2 lattice, and some Fe2O3 disperses on the surface of solid solution. The partial substitution of Ce4+ with Zr4+ and/or Fe3+ strongly improves the aging resistance of the catalysts. The strong synergetic effect between free Fe2O3 and surface oxygen vacancies wearies believed to have a pronounced positive effect on catalyst activity towards soot oxidation. Holding both the largest dopant content and well dispersed surfaceFe2O3, the Ce0.5Fe0.30Zr0.20O2 catalyst presents the lowest ti (251℃, ignition temperature of soot oxidation) and tp (310℃, temperature of maximum evolution of CO2). Even after aging for a long period at high temperature, the ti and tp values for Ce0.5Fe0.30Zr0.20O2 catalyst are still relatively low, at 273℃ and 361℃, respectively.
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