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 NO_x storage-reduction catalyst (NSR) was developed for automotive lean-burn engines. The NSR catalyst can store NO_x in an oxidizing atmosphere and then reduce stored NO_x at stoichiometric or reducing conditions. Also, it has high tolerance to sulfur poisoning which is the most stringent problem for the NSR catalyst.