Utilization of Advanced Pt/Rh TWC Technologies for Advanced Gasoline Applications with Different Cold Start Strategies

This paper describes the results of a joint development program focussing on the introduction of the new generation of Pt/Rh-technology for current and future emission standards as a cost effective alternative to the in serial Pd/Rh based exhaust gas concepts.

In the initial phase of the program combinations of Pd- and Pt-based three-way catalyst technologies were evaluated on vehicles equipped with a 8 cylinder engine. One goal in this portion of the study was to achieve technical equivalence between a viable Pd-based technology and the new Pt/Rh technology in the underfloor position at lower precious metal loading. A combination of a close-coupled Pd/Rh technology and the new Pt/Rh in the underfloor position was able to meet the emission targets at significant lower costs of the system after a catalyst aging that resembles more than 100.000 km of vehicle German highway driving.

In the later phase of the program the replacement of Pd/Rh by the use of Pt/Rh in the close coupled position as well as for the underfloor position was studied at two types modern vehicles. In addition, the influence of the cold-start strategy and the contribution of high-cell density substrates was elucidated.

In summary, these results prove that the new generation of Pt/Rh double layer technology is a technical and commercial attractive alternative to the in serial Pd-based double layer technologies for high demanding applications in close-coupled as well as in underfloor positions using different cold start strategies. Future development work will mainly focus on the further optimization of the precious metal content including an OBD-control function to monitor the catalyst activity for the alternative Pt/Rh catalyst.