Recent advances in automobile exhaust catalysts

Catalysts, which were recently developed by Toyota for the control of automobile exhaust, are reviewed. (1) For use in low emission vehicles, a CeO2-ZrO2 solid solution (CZ) with both high oxygen storage capacity and high heat resistance was developed as a support for a high performance three-way catalyst (TWC). (2) A novel three-way catalyst named the NOx storage-reduction catalyst (NSR) was developed for automotive lean-burn engines. The NSR catalyst can store NOx in an oxidizing atmosphere and then reduce stored NOx at stoichiometric or reducing conditions. Also, it has high tolerance to sulfur poisoning which is the most stringent problem for the NSR catalyst.