Development of Non-Ni Low H2 S Pt/Rh/CeO2 TWC Catalyst

A screening of new base metal oxides, which suppress H₂S formation in Pt/Rh/CeO₂ TWC catalysts, has been conducted using thermodynamic calculations.

As a result, several promissing candidates were found, and most of the candidates exhibited H₂S suppression effects in an engine H₂S formation test. However, many of these candidates for Pt/Rh/CeO₂ TWC catalyst negatively affected catalytic performance after thermal and engine agings. Among the candidates, the most prospective candidate as a non-Ni type H₂S scavenger was GeO₂.

Test results of an advanced type Pt/Rh/CeO₂ TWC catalyst with GeO₂ also showed both H₂S suppression effectiveness and no negative effects on catalytic performance. This catalyst is expected to be one of non-Ni low H₂S Pt/Rh/CeO₂ TWC catalyst candidates for near future applications.