The effect of the oxygen storage material on a three-way catalyst spatio-temporally resolved with Spaci-MS

Abstract

A methodology that allows the estimation of the stored oxygen (oxygen storage capacity (OSC)) along the TWC catalyst length by spatio-temporally resolving the O2 profiles during rich to lean cycle conditions with the use of the Spaci-MS technique has been developed. As a case study, the effect of the presence of mixed cerium-zirconium oxide as oxygen storage material has been investigated. The oxygen storage capacity for the TWC containing Ce material was much higher than without. The study also explores the reaction pathways typical of TWC along the catalyst coordinates by spatio-temporally resolving O2, H2, CO, and NO, as well as the related products and intermediates providing important understanding on, for example, the water-gas shift reaction leading to H2 production and how they develop differently depending on the OSM (oxygen storage material) in the catalyst. H2 production occurs closer to the front of the TWC length in the case of the catalyst without Ce, and results in an earlier production of undesired NH3 from NO reaction with H2. However, more N2O has been observed for the catalyst with Ce, which suggests the catalyst composition could be optimised to minimize overall secondary emissions.