Low-content and highly effective zoned Rh and Pd three-way catalysts for gasoline particulate filter potentially meeting Euro 7

Abstract

The next-generation Euro 7 standard proposed much lower pollutant limits from gasoline vehicles, specifically for CO and NOx, which would be challenging for the three-way catalysts (TWCs) utilized commercially to eliminate these pollutants. TWCs with reductive (Rh) and oxidative (Pd) active components on gasoline particulate filters (TWC on GPF) play importantly auxiliary roles in the remediation of CO and NOx downstream the close coupled TWCs to meet their emission targets. Here, a low-content Rh-based TWC (0.17 wt%) zoned with a less expensive Pd-based TWC (0.29 wt%) for GPF applications (cGPF) is reported using improved colloidal deposition method. The supporting of Rh on Y-stabilized ZrO2 rather than on CeO2–ZrO2 inhibits the formation of inactive Ce rhodate species, while Pd on CeO2–ZrO2 not only guarantees the high oxygen storage capacity (OSC) but also enhances catalytic activity. The layout of the front one-fifth in volume being 0.29 wt% Pd on Ce0.43Zr0.57O2 and the rear four-fifths being 0.17 wt% Rh on Zr0.85Y0.15O2 prevents the possible alloying of Rh with Pd. The highly effective zoned Rh and Pd TWCs show synergistic three-way activity before and after severe hydrothermal aging at 1000 °C with 10% water for 24 h, which could be potential choices for close coupled GPF application to satisfy the upcoming stringent emission standards, such as Euro 7 and China 6b.