Regeneration of sintered Rh/ZrO2 catalysts via Rh re-dispersion and Rh–ZrO2 interaction

Rh/ZrO2 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 O2 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 ZrO2 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 O2, was strongly related to the phase transformation of the ZrO2 support and the interaction between the Rh and tetragonal ZrO2 species.