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2011 Engines Review - Catalyst Page 2


Volvo Penta Catalyst


Illustration By Steve Karp

Exhaust gasses—also known as raw emissions—in the form of hydrocarbons, nitrogen oxide, and carbon monoxide [signified by the red dots in the image above] are common, yet toxic, outcomes of combustion engines. The gasses are awful for air quality and do much to harm the environment. They flow through a boat’s exhaust system and are chemically altered by a catalytic converter [the red boxes above] before being released into the outdoors. Once inside the converter, the gasses mingle with the exterior surfaces of a metal honeycomb that has been treated with a special wash coat made from the precious metals rhodium, palladium, and oftentimes platinum. A chemical reaction occurs that turns carbon monoxide (CO) into carbon dioxide (CO2), nitrogen oxide (NO) into nitrogen (N) and oxygen (O2), and unburned hydrocarbons into carbon dioxide (CO2) and water. So what eventually emerges in the exhaust stream is primarily a mixture of nitrogen, oxygen, carbon dioxide, and water. Best of all, this is accomplished without any moving parts.

(920) 929-5000.

Volvo Penta (757) 436-2800.

This article originally appeared in the June 2011 issue of Power & Motoryacht magazine.