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Rh/ZrO_2 catalyst was prepared by the impregnation method and then aged in N2 atmosphere with 10% steam at 1050°C for 12 h. The regeneration of the aged catalyst was examined by slow cooling the catalyst in O_2 following preheating at 950°C. The as-prepared, aged, and regenerated catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller specific surface area analysis, and(CO+NO) reaction activity tests, CO chemisorption, and transmission electron microscopy. The results revealed that the Rh species on ZrO_2 that underwent severe sintering during the high-temperature aging process could be regenerated by the slow re-oxidation process employed herein. Owing to the remarkable increase in the degree of Rh dispersion after the regeneration process, the activity could be markedly recovered. Further investigations revealed that such a regeneration phenomenon, involving the re-dispersion of the Rh species during the slow cooling process in O_2, was strongly related to the phase transformation of the ZrO_2 support and the interaction between the Rh and tetragonal ZrO_2 species.
Rh / ZrO 2 catalyst was prepared by the impregnation method and then aged in N2 atmosphere with 10% steam at 1050 ° C for 12 h. The regeneration of the aged catalyst was examined by slow cooling the catalyst in O_2 following preheating at 950 ° C. The as-prepared, aged, and regenerated catalysts were characterized by X-ray diffraction, Brunauer-Emmett-Teller specific surface area analysis, and (CO + NO) reaction activity tests, CO chemisorption, and transmission electron microscopy. the Rh species on ZrO 2 that underwent severe sintering during the high-temperature aging process could be regenerated by the slow re-oxidation process employed herein. Owing to the remarkable increase in the degree of Rh dispersion after the regeneration process, the activity could be markedly recovered. Further investigations revealed that such a regeneration phenomenon, involving the re-dispersion of the Rh species during the slow cooling process in O_2, was strongly related to the phase transformation of the ZrO 2 support and the interaction between the Rh and tetragonal ZrO 2 species.