Automotive Exhaust Technology after Treatment for the Reduction of Emission-A Review Study Narendrasinh R. Makwana 1 , Prof. Shyam K. Dabhi 2 ABSTRACT Today, modern cars emit up to 99% less exhaust pollutants than 30 years ago. But due to incomplete combustion in the engine, there are a number of incomplete combustion products CO, HC, NO x, particulate matters etc. These pollutants have negative impact on air quality as well as on human health. This paper gives an overview of the advanced technologies currently used for abating emissions from the gasoline and diesel internal combustion engines also discusses automotive exhaust emission and its harmful impact, automotive exhaust emission control technique, catalytic converter and its types, DOC, limitation of catalytic converter, DPF, SCR and also significance of catalytic converter. KEYWORDS- Exhaust emission, Catalytic Converter, Gasoline Application, DOC, DPF, SCR I. INTRODUCTION Automobiles are a „necessary evil‟, while they have made living easy and convenient; they have also made human life more complicated and vulnerable to both toxic emissions and an increased risk of accidents. Due to incomplete combustion in the engine, there are a number of incomplete combustion products CO, HC, NO x, particulate matters etc. These pollutants have negative impact on air quality as well as on human health also on environment that leads in stringent norms of pollutant emission. Numbers of alternative technologies like improvement in engine design, fuel pre-treatment, use of alternative fuels, fuel additives, exhaust treatment etc. are being considered to reduce the emission levels of engine. Among all the types of technologies developed so far, use of catalytic converters is the best way to control automotive exhaust emissions. This review paper discusses automotive exhaust emission and its harmful impact, automotive exhaust emission control technique, catalytic converter and its types, diesel oxidation catalyst, limitation of catalytic converter, diesel particulate filter, selective catalytic reduction and also significance of catalytic converter. II. EXHAUST EMISSION Due to incomplete combustion in the engine, there are a number of combustion products. Typical exhaust gas composition at the normal engine operating conditions is:  Carbon monoxide (CO, 0.5 vol. %)  Unburned hydrocarbons (HC, 350 vppm)  Nitrogen oxides (NO x , 900 vppm)  Hydrogen (H 2 , 0.17 vol. %)  Water (H 2 O, 10 vol. %)  Carbon dioxide (CO 2, 10 vol. %)  Oxygen (O 2 , 0.5 vol. %) HC, CO and NOx are the major pollutants. HC and CO occur because the combustion efficiency is < 100% due to incomplete mixing of gases and the wall quenching effects of the colder cylinder walls. The NOx is formed during the very high temperatures (>1500 0 C) of the combustion process resulting in thermal fixation of the nitrogen in the air which forms NOx. Hydrocarbons react in the presence of nitrogen oxides and sunlight to form ground- level ozone, a major component of smog. Ozone irritates the eyes, damages the lungs, and aggravates respiratory problems. Nitrogen oxides, like hydrocarbons, are precursors to the formation of ozone. They also contribute to the formation of acid rain. Carbon monoxide reduces the flow of oxygen in the blood stream and is particularly dangerous to person with heart disease. Carbon dioxide does not directly impact human health, but it is a “greenhouse gas” that traps the earth‟s heat and contributes to the potential for global warming. III. CATALYTIC CONVERTER A Catalytic converter is a device used to reduce the toxicity of emissions from an internal combustion engine. It was invented by Eugene Houdry, a French mechanical engineer and expert in catalytic oil refining who lived in the United States. About 1950, when the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of automobile exhaust in air pollution and founded a special company, Oxy- Catalyst, to develop catalytic converters for gasoline engines - an idea ahead of its time for which he was awarded a patent (US2742437). International Journal of Engineering Research & Technology (IJERT) Vol. 2 Issue 4, April - 2013 ISSN: 2278-0181 www.ijert.org 876