By-Pass Hydrocarbon Absorber System for ULEV

A by-pass zeolite adsorber system consisting of a first catalyst, a by-pass loop containing the zeolite adsorbers followed by a downstream second catalyst was FTP tested using a U.S. vehicle equipped with a 3.8 L, V6 engine. The system exhibited ULEV emissions performance with hydrocarbon adsorption and regeneration (desorption and oxidation) within the FTP cycle and required only a single diversion valve within the exhaust line. Adsorption takes place during the initial 70 seconds of the FTP cycle. The adsorbers were regenerated with the exhaust gas plus injected air.