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Measurements of oxygen storage capacity (OSC) and HC conversion efficiency for 17 catalysts were carried out in the laboratory. All catalysts with steady state HC efficiency below 90% were found to have roughly equivalent and very low capacities to store oxygen. However, catalyst oxygen storage capacity was seen to rise sharply with HC conversion efficiency in excess of 90 percent. These results parallel the trends which are observed between rear HEGO/EGO indexes for OBD-II catalyst monitoring and HC conversion efficiency. In addition, temperature programed reduction (TPR) was found to lend insight into the relationship between catalyst OSC and HC conversion efficiency by providing a qualitative understanding of the mechanisms by which OSC deteriorates. TPR profiles showed that most of the usable oxygen storage is derived from surface ceria which is interacted with precious metals.

The effect of MMT on the OBD-II catalyst efficiency monitor has been investigated. The results conclusively show that manganese which is deposited onto the catalyst during the combustion of MMT- containing fuel provides for an increased level of catalyst oxygen storage capacity. This added oxygen storage was found to result in a reduced rear EGO sensor response and caused malfunctioning catalysts to be incorrectly diagnosed by the OBD-II catalyst efficiency monitor.

This paper describes a study which was carried out to assess the potential for using a gasoline burner to heat the catalytic convertor during cold start. The results showed the catalyst/burner concept to be a promising LEV/ULEV capable technology. On a 1993 Ford Grand Marquis equipped with a catalyst burner system, catalyst light-off was achieved in less than 15 seconds while cold start HC emissions during the first 60 seconds of the FTP test were reduced by 60%. In addition, data are presented which compare the performance of the catalyst/burner to an electrically heated catalyst. In the tests performed, the catalyst/burner system out performed the EHC. Practical considerations, however, such as safety, durability, system integration, and packaging still need to be addressed.