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The general introduction of three-way catalysts in W-Europe starting in 1992 focusses again the attention of car manufacturers on the costs of the precious metals formulation. Three strategies to reduce those costs are discussed: 1. the decrease of the platinum/rhodium loading; 2. the replacement of platinum by palladium and 3. the combination of platinum/rhodium with palladium/rhodium catalysts. The results show that under appropriate conditions of use catalysts with about 20 US$/1 precious metal cost could be a valuable automotive emission control tool.

A commercial NOx-storage catalyst for gasoline applications containing Ba/CeO2/Al2O3, platinum, palladium and rhodium has been sulfated on the engine bench at 390 and 510°C with a nominal exposure of 1.3 g sulfur/liter catalyst. Lower exposures proved too low to have a notable impact on the catalytic performance. At 390°C the sulfur is completely adsorbed while at 510°C only partial adsorption is being observed. Sulfur is mainly deposited at the catalyst inlet thereby shielding the downstream region. Desulfation on synthetic gas bench at 700°C leads to a partial removal of the sulfur. The residual sulfur is more evenly distributed along the length of the catalyst compared to the sulfur profile in the sulfated catalyst. This causes an improvement of the NOx-activity at the inlet side while the NOx-performance at the outlet side decreases after desulfation.