Improved Coated Gasoline Particulate Filters for China 7 and US Tier 4 Legislations

The impending emission regulations in both China (CN7) and the United States (Tier 4) are set to impose more stringent emission limits on hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM). CN7 places particular emphasis on reducing particulate number (PN) thresholds, while the forthcoming United States Tier 4 legislation is primarily concerned with reducing the allowable particulate matter (PM) to an assumed limit of 0.5 mg/mile. Given the more stringent constraints on both PN and PM emissions, the development of enhanced aftertreatment solutions becomes imperative to comply with these new regulatory demands. Coated Gasoline Particulate Filters (cGPFs) play a pivotal role as essential components for effective PN and PM abatement. These filters are typically deployed in one of two configurations: close-coupled to the turbocharger positioned downstream of a primary three-way catalyst (TWC) or located further downstream of the exhaust system in an underfloor configuration. Each application imposes distinct technical requirements and specifications on cGPFs, necessitating tailored solutions for both close-coupled and underfloor applications. This research introduces a novel generation of particulate filters optimized for pressure drop and underfloor applications, which exhibit improved performance in terms of light-off and hot conversion efficiency while maintaining comparable backpressure levels to its predecessors. Moreover, a suite of advanced technologies for close-coupled applications is presented, featuring improved three-way conversion efficiency and enhanced thermal durability compared to previous iterations. Significantly, these new technologies demonstrate equivalent three-way conversion capabilities, irrespective of whether employing bi-metallic Pd/Rh or tri-metallic Pt/Pd/Rh Platinum-group-metal (PGM) architectures. Lastly, the study undertakes an analysis of the trade-off between backpressure and the gain in three-way conversion activity provided by these innovative technologies.