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A Cu/ZSM-5 catalyst has been tested in both the laboratory and in a gasoline-fueled, lean-burn car. This catalyst is generally believed to be the current “state of the art” for removing NOx from lean engine exhaust. The laboratory tests showed that the HC species was the exhaust component which reduced the NOx. This catalyst actually produced CO, but the CO had no impact on the NOx reduction. The NOx conversion was inhibited by oxygen at oxygen levels below 4%, but was also modestly inhibited by oxygen levels above 4%. The NOx, conversion of these catalysts was less affected by SO2 than were the HC and CO conversions. These catalysts showed very poor thermal durability, losing much of their activity after aging under conditions milder than those typically used for three-way catalysts. The vehicle tests of the fresh Cu/ZSM-5 catalyst showed between 30 and 40% average NOx conversion.

The following study was performed to investigate the in-use emissions performance of a California TLEV equipped with components aged in customer service on an enhanced I/M test. Fuels and ambient temperature conditions were chosen to compare I/M test conditions typical for California (moderate temperature on California Phase II gasoline) to those likely to be encountered in a Northeastern state (cold temperature on Winter grade fuel). To obtain repeatable results and simulate typical customer driving prior to the test, Bag II of the FTP schedule was used to simulate urban driving to an I/M lane, followed by a variable length idle to simulate waiting for the I/M test, followed by the IM240 test.