Design and Performance Evaluation of Automotive Emission Control Catalysts

Behavior of Non-Promoted and Ceria-Promoted Pt/Rh and Pd/Rh Three-Way Catalysts under Steady State and Dynamic Operation of Hybrid Vehicles

“…The drop in CO conversion above 300 °C can be ascribed to higher steam-reforming activity of the catalysts, thus producing additional CO. Ceria promotion generally enhanced the efficiency of the palladium catalyst for CO oxidation (Table ), whereas no clear effect is observable for the Pt catalysts. An improvement of CO oxidation activity by ceria was occasionally reported for platinum metal-based catalysts. ,,, Kim 29 attributed the improved CO removal upon ceria promotion of TWCs to the enhanced activity for the water−gas shift reaction and, in part, to the additional oxygen storage it provides to the TWC.…”

“…An improvement of CO oxidation activity by ceria was occasionally reported for platinum metal-based catalysts. 28,31,33,34 Kim 29 attributed the improved CO removal upon ceria promotion of TWCs to the enhanced activity for the water-gas shift reaction and, in part, to the additional oxygen storage it provides to the TWC.…”

“…The classical promotion by ceria has been complemented by adding lanthana and other rare earth or alkaline metal oxides. ,,, Better NO x reduction performance 19,20 with and without the addition of base metal oxides, as well as improved high-temperature stability 14,20 and better HC conversion behavior, have been reported. The addition of ceria as one of the most important promoters was observed as stabilizing the alumina wash coat, , increasing and stabilizing the noble-metal dispersion, enhancing the oxygen storage capacity of the catalysts, and enhancing the activity for the water−gas shift reaction (WGSR). , …”

“…10,20,25,26 Better NO x reduction performance 19,20 with and without the addition of base metal oxides, as well as improved high-temperature stability 14,20 and better HC conversion behavior, 27 have been reported. The addition of ceria as one of the most important promoters was observed as stabilizing the alumina wash coat, 28,29 increasing and stabilizing the noble-metal dispersion, 30 enhancing the oxygen storage capacity of the catalysts, 29 and enhancing the activity for the water-gas shift reaction (WGSR). 29,30 In this study, a set of commercially available new technology non-promoted and ceria-promoted Pd-Rh catalysts have been compared with analogous standard Pt-Rh three-way catalysts.…”

Environmental Catalysis: Mobile Sources

“…In the design of a three-way catalyst, multilayered washcoating strategies are important in separating catalyst components, which, over time, react with each other leading to deactivation; appropriate strategies can facilitate positive synergistic interactions as well (Silver et al 1991). Figure 10.9 illustrates an example of a strategy for (i) minimizing Rh-AI203 interaction by isolating the Rh in the pores of a non-reactive Zr02 support in a phase separate from that of Pt/La203-BaO/AI2O3, (ii) maximizing oxygen storage capacity, CO oxidation and the water-gas shift reaction by stabilizing CeOt through incorporation in a solid solution with Zr02, (iii) placing PdO and the Ce02/Zr02 OSM in catalyst layer 1, thereby protecting them from poisoning by SO2 through the use of the two upper layers (layer 2 and the A1203 layer) that serve as reactioddiffusion barriers.…”