Influence of Oxygen Storage Characteristics on Automobile Emissions

The catalytic performance and On-Board Diagnostics (OBD) of the manifold catalyst having high Oxygen Storage Capacity (OSC) are described in this paper.

First of all, we compared the performance of three-way catalysts containing Cerium - Zirconium - Yttrium oxide with Cerium - Zirconium oxide. Three-way catalysts dispersed Pt, Rh and Pd on Cerium - Zirconium - Yttrium oxide showed excellent catalytic performance especially at cold starting and at transient states, after high temperature aging at 1050°C. The performance of these catalysts was studied using the Driving Mode Simulation Dynamometer, which was developed in-house, and oxygen storage and release responses were compared in actual gas.

Then we investigated the possibility of on-board diagnostics of catalyst deactivation with high OSC in manifold and close-coupled positions, a diagnostic which is usually assumed to be difficult to attain with present conventional technology. We achieved finding a correlation between the HC emission of catalysts and the delay in response of two exhaust gas sensors even at high temperatures (700°C) with high gas flow rate.