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I would say that removing 11% carbon monoxide from an exhaust gas is quite a challenge. By my estimation, if you were to combust it in one step, the temperature rise in the catalyst bed would be ~ 900ºC – severely limiting the lifetime of most PGM catalysts.

My recommendation would be to dilute the exhaust gas with air (to about 1–2% CO); air dilution will be necessary to bring down the exotherm and is needed for the CO oxidation. However, adding air (unless it is hot) will lower the exhaust-gas temperature, and make light-off more difficult. In which case, it may be better to use one of our advanced oxidation catalysts (developed for homogeneous charge compression ignition (HCCI) engines).

The maximum temperature for oxidation catalyst, that we guarantee, is ~ 1250°F or 675°C.

Another option might be to inject water and then use a water gas shift catalyst to produce hydrogen, while reducing CO. The H₂ may be useful in another process or sold as a product.

Comments

It is assumed that these details refer to a stationery application.

The more detailed information needed from the questioner to help answer this problem needs input from one of Johnson Matthey’s business groups, knowledgeable about catalysts for all types of engines. They will help in identifying appropriate technology.

You are most welcome to visit our website at http://ect.jmcatalysts.com/, Emission Control Technologies (ECT) and contact any one of us for advice.

Answer posted 3 June 2005