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Tuesday, November 6, 2012

Catalytic Converter

Catalytic converter is a device that put into vehicle muffler to reduce air pollution. The device contains hexagonal ceramics (like bee nest) layering aluminium oxide and it is filled with catalytic metal like platinum (Pt), palladium (Pd) and rhodium (Rd). Exhaust gas of vehicle is passed through hot catalytic chambers so CO gas and hydrocarbon compounds are oxidized, whereas oxides of nitrogen (NOx) are reduced.

Initially, catalytic converter is specified for oxidation process. Now, the converter is designed for analyzing both oxidation and reduction reactions that its influence becomes better for environment. Converter is designed to have wide surface that will be efficient in changing poisonous gases into non-pollutants.

Problem arises when catalytic converter must be heated first (≥600K) to be effective. Such condition prevents catalyst work effectively when a new machine is started and at the first journey. Converter with electric heating has been designed, but it may empty car storage battery. In 1994, researchers in Tutfs University, USA had a new idea, namely by involving reversible dehydration of lithium bromide (LiBr). When the vehicle is running and the machine becomes hot, hydrated LiBr is dehydrated. As it is rehydrated, the energy released can be used to heat catalytic converter just before ignition. But, the process has not yet been adopted commercially.

It is important to note that catalytic converter can only be used for vehicle using petrol without a lead because it can damage the function of its catalysts. In addition, pollutant will settle on catalyst surface and poisonous that the catalyst must be changed every five or six years.


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