bstract-A major cause ofair pollutionisthe emisson from vehicles and this cause has turned out to be a major concern as the population of vehicles on the road is increasing rapidly, henceit is predictedl that the levelof pollutants present in the air will escalate in the future as the incomplete combustion process of fossil fjuels leads to the production of products ilke 'carbon monoxide, oxides of nitrogen, hydrogen carbon and particulate matter which further leads to increment in the level ofemissions. To control the emission level for reducing air pollution, various methods are applied and one of them brings the use ofcatalytic converter,which involves the use of various materials like platinum, palladium, rhodium, copper, cobalt oxide,titanium dioxide and iron-exchange zelite which act as an auto catalyst to reduce harmful emisions to a certain level. The effectiveness of different types of catalytic converters has a major impact on the level ofemission.
2. NEED OF CATALYTIC CONVERTER
The catalytic converter is the best device to meet the strict exhaust emission limits as it converts the hydrocarbon, carbon monoxide, and oxides of nitrogen into less harmful gases by using a catalyst [3]. An alternative method for emission reduction s t increase he combustion temperature which ensures more complete burning takes place, but this increment leads to the formation of the third major pollutant, oxides of nitrogen. The converter forms a chamber for catalytic materialin the exhaust system through which when the exhaust gas passes in the presence of oxygen the HC and CO compounds combine with oxygen giving rise to harmless by-products.
3. TYPES OF CATALYTIC CONVERTER
Key Words: Catalytic Converter, Catalyst, Emissions, Effectiveness, Noble Group.
Two Way Catalytic Converter- Atwo-way catalytic converter performs two tasks simultaneously, oxidation of carbon monoxide o carbon dioxide and oxidation of hydrocarbons to carbon dioxide and water, as shown in figure 1. It has two separate elements one for nitrogen oxide and other forhydrocarbons/carbon monoxide.Theconverter has an axial flow and secondary air is injected ahead of the first element.
1.INTRODUCTION
Over the past decade or two, there has been a significant increment in the number of vehicles present on the roads, which in return makes them a major cause of deterioration of the air quality, so further cuts in pollution per vehicle are needed to keep improving the air quality, as around 1/3 of the contamination of the air is from automobile fleet[1]. So here the use of catalytic converters comes in the picture. A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less toxic pollutants by catalyzinga redox reaction 12.
Theprocess of Catalyzing is performed with the application of various materials like platinum, rhodium, pailadium, copper, cobalt oxide, etc which act as an autocatalyst resulting in a significant drop in the levels of pollutants emitted by vehicles which in return leads to improvement in the air quality.Usually, noble group metals like platinum, palladium, and rhodium are used as autocatalyst because of their superiority in the ability to work as a reducing or oxidizing agent for the conversion of toxic pollutants like nitrogen oxide, carbon monoxide, etc intoless harmful gases like nitrogen and carbon dioxide. But the cost of production of catalytic converter that incorporates the use of noble group metals is high so as an alternative option, materials ike oxides of copper, titanium, and cobalt are used as they are inexpensive and readily available
Rechcing ElementlorNl.,
Skcstny Air
ONidsrg Femet For HC/CO
Exhaust Gas Out
Figure 1: Two Way Catalytic Converter
4HC + 5 02-5 4 C02+ 2 H10 (Oxidatton of hydrocarbon)
2 CO + 02-> 2 COz(Oxidation of carbon monoxide)
Three Way Catalytic Converter-Three-way atalytic converters have the advantage of regulating the emissions of oxides ofnitrogen.
A three-waycatalytic converterperforms simultaneous tasks, reduction ofnitrogen oxides to nitrogen, oxidation of carbon monoxide to carbon dioxide and oxidation of unburnt hydrocarbons to carbon dioxide and