Catalysts for Gasoline Fueled Spark Ignition Engines

Neither the fuel additive nor the catalytic soot combustion coating have the ability to substantially reduce the emission of carbon monoxide or aldehydes. To achieve this, a different, precious metal based, catalytic coating can be applied to the filter, or a precious metal based catalyst can be added in line with the filter system. To date, filtering systems have not reached widespread application, mainly because of the high costs associated with their complexity. 

A simpler way to achieve a considerable reduction in the mass of particulates emitted, is the use of special diesel oxidation catalysts (Section 1.4). They offer advantages over filtering devices as they are simple, cost effective and can also reduce the emissions of CO, gaseous hydrocarbons, aldehydes and polynuclear aromatic hydrocarbons. Their main disadvantage is that their particulate mass reduction efficiency is only about half that achieved by filtering devices. 

Finally, it is worthy of mention that the patent literature discloses many unconventional ways to reduce tailpipe emission of particulate matter for example, the use of electrostatic precipitation, cyclones or gaswashing devices. However, none of these has reached practical application [13]. 

3 Catalysts for Gasoline Fueled Spark Ignition Engines 

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