Abstract:

Typically, an engine/dynamometer thermal-aging cycle contains combinations of elevated catalyst inlet temperatures, chemical reaction-induced thermal excursions (simulating misfire events), and average air/fuel ratio's (AFR's) to create a condition that accelerates the aging of the test part. In theory, thermal aging is predominantly a function of the time at an exposure temperature. Therefore, if a burner system can be used to simulate the exhaust AFR and catalyst inlet and bed temperature profile generated by an engine running an accelerated aging cycle, then a catalyst should thermally age the same when exposed to either exhaust stream.

This paper describes the results of a study that examined the aging difference between six like catalysts aged using the Rapid Aging Test (RAT) cycle (an accelerated thermal aging cycle). Three catalysts were aged using a gasoline-fueled engine-aging stand; the other three were aged using a computer-controlled burner system. Both systems were programmed to run aging cycles that provided the same inlet temperature and AFR profiles, and space velocity conditions. Each catalyst was evaluated using a vehicle over the FTP emissions test cycle and an AFR sweep test using an engine test stand before and after aging. Finally, the catalysts were cored and analyzed to provide a composition and surface area comparison.

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