A catalyst composition has an upstream stage and a downstream stage, the upstream stage containing a catalytic material which is different from the catalytic material contained on the downstream stage and is characterized by having a low ignition temperature, e.g., 350.degree. C. to less than 400.degree....http://www.google.co.uk/patents/US5531972?utm_source=gb-gplus-sharePatent US5531972 - Staged three-way conversion catalyst and method of using the same
