A rhodium catalyst supported on AlPO4 exhibited a much higher resistance to sulfur and phosphorus poisoning compared with a reference catalyst (Rh/Al2O3). The acidic surface of AlPO4 was effective in preventing the adsorption of sulfur oxides (SO2), whereas Lewis acid/base sites on Al2O3 favored, SO, adsorption followed by the formation of sulfite, leading to deterioration of the activity of Rh/Al2O3 for the model NO-CO-C3H6-O-2 reaction. Similarly, the AlPO4 support suppressed the extent of phosphorus poisoning caused by dimethylphosphite (DMP) (CH3O)(2)POH, which was used as a model phosphorus source. A greater amount of inactive phosphate overlayers were deposited from the gas feed containing DMP and O-2 on Rh/Al2O3 than Rh/AlPO4 because of the reaction between P2O5 vapors and Al2O3. Consequently, the active Rh surface was covered to a greater extent for Rh/Al2O3 than Rh/AlPO4.