Opportunities and Challenges for Blended 2-Way SCR/DPF Aftertreatment Technologies

Diesel engines offer better fuel economy compared to their gasoline counterpart, but simultaneous control of NOx and particulates is very challenging. The blended 2-way SCR/DPF is recently emerging as a compact and cost-effective technology to reduce NOx and particulates from diesel exhaust using a single aftertreatment device. By coating SCR catalysts on and inside the walls of the conventional wall-flow filter, the 2-way SCR/DPF eliminates the volume and mass of the conventional SCR device. Compared with the conventional diesel aftertreatment system with a SCR and a DPF, the 2-way SCR/DPF technology offers the potential of significant cost saving and packaging flexibility.

In this study, an engine dynamometer test cell was set up to repeatedly load and regenerate the SCR/DPF devices to mimic catalyst aging experienced during periodic high-temperature soot regenerations in the real world. The emission reduction performances of the engine-aged 2-way SCR/DPF devices with various SCR formulations from different suppliers were evaluated on a pick-up truck during the cold-start FTP and US06 tests. Furthermore, the 2-way SCR/DPF was benchmarked and compared with the conventional DPF in terms of flow restriction and soot regeneration efficiency. The emission reduction performance evaluation of the blended 2-way SCR/DPF devices after real-world engine aging provides valuable data and critical guidance to develop future cost-effective and compact diesel aftertreatment system to meet forthcoming US Tier 2 Bin 5 and Euro VI diesel emissions standards.