Patent ID: 8578704

Claim:
A method of operating a catalytic system for reducing emissions from a rich burn spark-ignited engine, comprising: controlling intake air and fuel (AFR) to produce first exhaust gases substantially free of oxygen; passing said first exhaust gases into a first-stage catalyst chamber containing a three-way catalyst (TWC) operating above 800° F., which minimizes NOx content by reducing NOx (to N 2 and O 2 ); passing exhaust gases exiting from the first-stage catalyst chamber to an inter-stage cooling chamber having a) cooling means, and cooling by-pass means, which are used to adjust gas temperature to a controlled Tmix =390 -520° F., and b) secondary air injection means, which enriches the oxygen content to about 0.25- 1.0%; passing exhaust gases exiting from the inter-stage cooling chamber to a second-stage catalyst chamber containing a catalyst that minimizes CO content by oxidizing CO to CO 2 .