Development and system application of an ultra-low loaded precious metal catalyst technology on LEV2 vehicles

摘要

Within the next decade, all light-duty vehicles in the United States will be required to meet Tier 2 or LEV 2 tailpipe emission standards. As emission standards have tightened over time catalyst systems have increased in cost. The factors that have contributed to the growth in cost include increases in both precious metal content and catalyst volumes. Calibration strategy, catalyst, and substrate technology improvements have also enabled previous emission standards to be met. The recent dramatic fluctuations in precious metal price, coupled with the increasing desire to reduce system cost, have led catalyst companies to develop converter technologies containing decreasing amounts of precious metal, and still meet Tier 2/LEV2 standards. In this paper the development of a novel, near base metal, catalyst technology is described. The effects of precious metal support type and catalyst preparation method are reported using model engine bench and vehicle tests. The application of this novel catalyst technology to a LEV2 light-duty truck is then detailed. The effects of underbody and close-coupled precious metal load were studied. Data demonstrating the performance of this catalyst in low volume (85% ESV), and low precious metal loading, systems is described. LEV2 emission standards are met on a fully aged system with less than 2 g of precious metal.