Cold-Start Hydrocarbon Collection for Advanced Exhaust Emission Control

This paper describes the findings of a laboratory effort to demonstrate improved automotive exhaust emission control with a cold-start hydrocarbon collection system. The emission control strategy developed in this study incorporated a zeolite molecular sieve in the exhaust system to collect cold-start hydrocarbons for subsequent release to an active catalytic converter. A prototype emission control system was designed and tested on a gasoline-fueled vehicle. Continuous raw exhaust emission measurements upstream and downstream of the zeolite molecular sieve revealed collection, storage, and release of cold-start hydrocarbons. Federal Test Procedure (FTP) emission results show a 35 percent reduction in hydrocarbons emitted during the cold-transient segment (Bag 1) due to adsorption by the zeolite. Furthermore, this paper identifies future development needs, namely improvements in adsorption capability, system purging of the collected pollutants, and a complete on-vehicle system demonstration. In this study, zeolite molecular sieves have been shown to be potentially capable of improving control of cold-start emissions. Such a capability suggests the possible future use of zeolite molecular sieves in advanced automotive exhaust aftertreatment systems.