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A new adsorber system for reducing cold start HC emissions has been developed that offers a passive and simplified alternative to previous HC adsorber technologies. The series flow in-line adsorber concept combines existing catalyst technology with a zeolite based HC adsorber by simply incorporating one additional adsorber catalyst substrate into conventional catalytic converters without any valving, purging lines or special substrates. The HC adsorber catalyst consist of a durable zeolite, a washcoat binder, precious group metals and rare earth promoters on standard monolithic substrates. For selected vehicle applications, a single converter containing a light off catalyst, a catalyzed HC adsorber and a standard three-way catalyst can be used in the underfloor position. Even after severe engine aging, the vehicle FTP results show that this new technology remains effective in reducing the cold start HC emissions while providing good CO and NOx conversions.

Close-coupled or manifold catalysts have been extensively employed to reduce emissions during cold start by achieving quick catalyst light-off. These catalysts must have good thermal durability, high intrinsic light-off activity and high HC/CO/NOx conversions at high temperature and flow conditions. A number of studies have been dedicated to engine control, manifold design and converter optimization to reduce cold start emissions. The current paper focuses on the effect of catalyst design parameters and their performance response to different engine operating conditions. Key design parameters such as catalyst formulation (CeO2 vs. non CeO2), precious metal loading and composition (Pd vs. Pd/Rh), washcoat loading, catalyst thermal mass, substrate properties and key application (in use) parameters such as catalyst aging, exhaust A/F ratio, A/F ratio modulation, exhaust temperature, temperature rise rate and exhaust flow rate were studied on engine dynamometers in a systematic manner.

SCR on filter, also known as SCRoF, SCRF, SDPF, has been utilized to meet the stringent light duty Euro 6 emission regulations. Close-coupled DOC-DEF-SCR on filter with underfloor SCR architectures, offer a balance of NOx performance at cold start and highway driving conditions. In contrast, the DOC-DPF-DEF-SCR architecture has been most commonly selected to meet the on-road and non-road heavy duty emission regulations worldwide. Diesel engines applied to off road vehicles can operate under higher loads for extended times, producing higher exhaust temperatures and engine out NOx emissions. New European Stage V emission regulations will mandate diesel particulate filter (DPF) adoption because of particulate number and more stringent particulate mass requirements. Three aftertreatment architecture choices with diesel particulate filters (DPF) were evaluated as candidates to fulfill the Stage V emission regulations.