All You Need To Know About The Catalytic Convertor
Posted: Aug 16, 2016
Catalytic converter is a device which controls emission and converts toxic gases and exhaust gases into a less toxic form. Catalytic converter works on the principle of catalyzing a redox reaction. The devices are commonly used in automobiles, trucks, buses, motorcycle, and the like. It works best when heated to an optimum temperature. Catalytic converters are mainly used in internal combustion engines. There are 3 types of catalytic converter –
Two-way catalytic converter
This cycle mainly helps in reducing hydrocarbons and carbon monoxide emissions, thus are mainly used in diesel engines. These devices were replaced by three-way catalytic because two-way catalytic converters were unable to control the oxides of nitrogen. The two-way catalytic converters only have reduction capabilities. Two simultaneous tasks take place in two-way catalytic converter, namely:
1. Oxidation of carbon monoxide to carbon dioxide:
2CO + O2? 2CO2
2. Oxidation of hydrocarbons or in other words unburnt fuels to carbon dioxide and water:
CxH2x+2 + [(3x+1)/2] O2? xCO2 + (x+1) H2O(a combustion reaction)
Three-way catalytic converter
Three-way catalytic converter eliminates gases like nitrogen oxide emissions, carbon monoxide and hydrocarbons or in other words, unburnt fuels. Three-way catalytic converter consists of two blocks - one is reduction catalyst and another is oxidation catalyst. The reduction catalyst consists of rhodium and platinum and the oxidation catalyst consists of platinum and palladium. The primary catalyst breaks nitrogen oxides into nitrogen (N2) and oxygen (O2). The secondary catalyst treats carbon monoxide and hydrocarbon, carbon monoxide pairs with oxygen and forms carbon dioxide (CO2), and hydrocarbon pairs with oxygen and forms water (H2O) and carbon dioxide (CO2). Three-way catalytic converters have 90% efficiency so there are still some harmful gases which are not treated.
1. Reduction of nitrogen oxides to nitrogen and oxygen:
2NOx? xO2 + N2
2. Oxidation of carbon monoxide to carbon dioxide:
2CO + O2? 2CO2
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water:
CxH2x+2 + [(3x+1)/2]O2? xCO2 + (x+1)H2O.
Diesel oxidation catalytic converter
The concept behind the oxidation catalyst is that it causes a chemical reaction to occur at lower temperatures without being changed or consumed. The oxidation catalytic converter consists of a stainless steel canister that typically contains a honeycomb like structure. The honeycomb like structure is called substrate. There are no moving parts, just a very large area of interior surfaces on the substrate coated with catalytic metal. In the case of diesel exhaust, the catalyst oxides carbon monoxide, gaseous hydrocarbon, unburnt fuel and oil absorbed on the carbon particle. The unburnt fuel and oil are referred to as the volatile or soluble organic fraction and can make up a significant part of the total particulate matter. A flow through oxidation catalytic converter installed on a vehicle can reduce the soluble organic fraction of particulate by as much as 90% and total particulate by as much as approximately 25%-50% depending upon the composition of the particulate being emitted plus, it can virtually eliminate the obnoxious odor of the diesel exhaust. Destruction of the soluble organic fraction is important since this portion of the particulate emissions contains numerous chemical pollutants that are the particular concerns of health experts. Furthermore, reduction of 60% to 90% of carbon monoxide and gaseous hydrocarbons emissions can be achieved. As a result the diesel oxidation catalyst has become a leading retrofit control strategy in the both on-road and non-road sectors throughout the world.
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About The Author
Benjamin Harvey is a mechanical engineer specializing in automobiles, and is closely associated with working and researching on catalytic converters. He is of the opinion that www.globalrefininggroup.com is the best destination to sell catalytic converters.
Benjamin Harvey is a mechanical engineer specializing in automobiles, and is closely associated with working and researching on catalytic converters.