High OSC CeO2/ZrO2 Mixed Oxides Used as Preferred Metal Carriers for Advanced Catalysts 2007-01-1057
Thermally stable CeO2/ZrO2 oxygen storage materials [1, 2, 3, 4, 5, 6 and 7] are necessary to get advanced TWC catalysts complying with the more severe regulations.
In addition to the thermal stability, the increase of the bulk oxygen mobility of the CeO2/ZrO2 mixed oxides is of great interest to boost the conversion of the pollutants under transient modes and during the cold start operations as well.
This paper deals with the recent progress achieved in the preparation of thermo-stable highly reducible mixed oxides. Thanks to a new process, with mild conditions, Rhodia developed new CeO2/ZrO2 mixed oxides with outstanding oxygen availability as well as high surface area over the whole composition range . These materials show a pure solid solution and a BET surface area higher than 20 m2/g after air ageing at 1100°C.
This paper shows that the use of these new materials as both Rh or Pd carriers yields better catalytic activity in dynamic scan tests as well as under light-off conditions.
A significant increase in NOx conversion is evidenced on Pd-based model catalysts and a higher activity at the cross-over-point is showed on Rh-based model catalysts even after long term (48 hours) ageing at high temperature (1050°C). In addition the decrease of Rh loading (by about 25%) does not significantly impact the catalytic activity.