Pt substitution in Pd/Rh three-way catalyst for improved emission control

Gasoline engine vehicle emissions, such as nitrogen oxides (NOx), CO and hydrocarbons (HCs), are a major source of air pollution, and require improved emission control systems. By-product NH3 and N2O emissions, which come from low N-2 selectivity in the emission control system, are also a major concern. The current study has comprehensively investigated the impact of the Pt-substitution in commercial Pd/Rh-based three-way catalyst (TWC) formulations with respect to catalytic performance. TWC performance was systematically evaluated with respect to the warm-up catalytic converter (WCC) and the under-floor catalytic converter (UCC). This included evaluating TWC activity under realistic simulated exhaust conditions including fuel-rich, stoichiometric and fuel-lean (0.99 <=lambda <= 1.01). Pt-substituted TWCs outperformed Pd-based counterparts, regardless of the converter type (WCC or UCC), in CO, C3H6 and C3H8 oxidation and NO reduction reactions under the simulated exhaust conditions tested. Moreover, Pt-substituted TWCs exhibited significant stability upon hydrothermal aging at 1,050 degrees C. The results show that after aging the Pt-substituted catalyst retained higher N-2 selectivity than the Pd-based TWC. Over Pd-based TWCs, N-2 selectivity drastically dropped from 70-80% to 15-35% after aging, while Pt-substituted TWCs N-2 selectivity dropped from 80-100% to only 60-80%. The key finding from this study is that Pt incorporation in a Pd/Rh TWC improves the emission control from gasoline vehicles in terms of both CO and HC oxidation and NOx reduction.

Automated summary

Gasoline engine vehicle emissions, such as nitrogen oxides (NOx), CO and hydrocarbons (HCs), are a major source of air pollution. This study investigated the impact of substituting platinum in commercial catalyst formulations on catalytic performance. The results showed that platinum-substituted catalysts outperformed palladium-based counterparts in terms of CO and HC oxidation as well as NOx reduction, and exhibited significant stability after hydrothermal aging at 1050℃.